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423 Commits
| Author | SHA1 | Message | Date | |
|---|---|---|---|---|
Adrian Hunter
|
135225a363 |
timekeeping: Let timekeeping_cycles_to_ns() handle both under and overflow
For the case !CONFIG_CLOCKSOURCE_VALIDATE_LAST_CYCLE, forego overflow protection in the range (mask << 1) < delta <= mask, and interpret it always as an inconsistency between CPU clock values. That allows slightly neater code, and it is on a slow path so has no effect on performance. Suggested-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Adrian Hunter <adrian.hunter@intel.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Link: https://lore.kernel.org/r/20240325064023.2997-19-adrian.hunter@intel.com |
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Adrian Hunter
|
fcf190c369 |
timekeeping: Make delta calculation overflow safe
Kernel timekeeping is designed to keep the change in cycles (since the last timer interrupt) below max_cycles, which prevents multiplication overflow when converting cycles to nanoseconds. However, if timer interrupts stop, the calculation will eventually overflow. Add protection against that. In timekeeping_cycles_to_ns() calculation, check against max_cycles, falling back to a slower higher precision calculation. In timekeeping_forward_now(), process delta in chunks of at most max_cycles. Suggested-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Adrian Hunter <adrian.hunter@intel.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Link: https://lore.kernel.org/r/20240325064023.2997-18-adrian.hunter@intel.com |
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Adrian Hunter
|
e809a80aa0 |
timekeeping: Prepare timekeeping_cycles_to_ns() for overflow safety
Open code clocksource_delta() in timekeeping_cycles_to_ns() so that overflow safety can be added efficiently. Suggested-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Adrian Hunter <adrian.hunter@intel.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Link: https://lore.kernel.org/r/20240325064023.2997-17-adrian.hunter@intel.com |
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Adrian Hunter
|
3094c6db1c |
timekeeping: Fold in timekeeping_delta_to_ns()
timekeeping_delta_to_ns() is now called only from timekeeping_cycles_to_ns(), and it is not useful otherwise. Simplify the code by folding it into timekeeping_cycles_to_ns(). No functional change. Suggested-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Adrian Hunter <adrian.hunter@intel.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Link: https://lore.kernel.org/r/20240325064023.2997-16-adrian.hunter@intel.com |
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Adrian Hunter
|
e84f43e34f |
timekeeping: Consolidate timekeeping helpers
Consolidate timekeeping helpers, making use of timekeeping_cycles_to_ns() in preference to directly using timekeeping_delta_to_ns(). No functional change. Suggested-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Adrian Hunter <adrian.hunter@intel.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Link: https://lore.kernel.org/r/20240325064023.2997-15-adrian.hunter@intel.com |
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Adrian Hunter
|
e8e9d21a5d |
timekeeping: Refactor timekeeping helpers
Simplify the usage of timekeeping sanity checking, in preparation for consolidating timekeeping helpers. This works towards eliminating timekeeping_delta_to_ns() in favour of timekeeping_cycles_to_ns(). No functional change. Suggested-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Adrian Hunter <adrian.hunter@intel.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Link: https://lore.kernel.org/r/20240325064023.2997-14-adrian.hunter@intel.com |
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Adrian Hunter
|
670be12ba8 |
timekeeping: Reuse timekeeping_cycles_to_ns()
Simplify __timekeeping_get_ns() by reusing timekeeping_cycles_to_ns(). No functional change. Suggested-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Adrian Hunter <adrian.hunter@intel.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Link: https://lore.kernel.org/r/20240325064023.2997-13-adrian.hunter@intel.com |
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Adrian Hunter
|
9af4548e82 |
timekeeping: Tidy timekeeping_cycles_to_ns() slightly
Put together declaration and initialization of the local variable 'delta'. Suggested-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Adrian Hunter <adrian.hunter@intel.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Link: https://lore.kernel.org/r/20240325064023.2997-12-adrian.hunter@intel.com |
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Adrian Hunter
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a729a63c6b |
timekeeping: Rename fast_tk_get_delta_ns() to __timekeeping_get_ns()
Rename fast_tk_get_delta_ns() to __timekeeping_get_ns() to prepare for its reuse as a general timekeeping helper function. Suggested-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Adrian Hunter <adrian.hunter@intel.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Link: https://lore.kernel.org/r/20240325064023.2997-11-adrian.hunter@intel.com |
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Adrian Hunter
|
e98ab3d415 |
timekeeping: Move timekeeping helper functions
Move timekeeping helper functions to prepare for their reuse. Suggested-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Adrian Hunter <adrian.hunter@intel.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Link: https://lore.kernel.org/r/20240325064023.2997-10-adrian.hunter@intel.com |
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Linus Torvalds
|
d08c407f71 |
A large set of updates and features for timers and timekeeping:
- The hierarchical timer pull model
When timer wheel timers are armed they are placed into the timer wheel
of a CPU which is likely to be busy at the time of expiry. This is done
to avoid wakeups on potentially idle CPUs.
This is wrong in several aspects:
1) The heuristics to select the target CPU are wrong by
definition as the chance to get the prediction right is close
to zero.
2) Due to #1 it is possible that timers are accumulated on a
single target CPU
3) The required computation in the enqueue path is just overhead for
dubious value especially under the consideration that the vast
majority of timer wheel timers are either canceled or rearmed
before they expire.
The timer pull model avoids the above by removing the target
computation on enqueue and queueing timers always on the CPU on which
they get armed.
This is achieved by having separate wheels for CPU pinned timers and
global timers which do not care about where they expire.
As long as a CPU is busy it handles both the pinned and the global
timers which are queued on the CPU local timer wheels.
When a CPU goes idle it evaluates its own timer wheels:
- If the first expiring timer is a pinned timer, then the global
timers can be ignored as the CPU will wake up before they expire.
- If the first expiring timer is a global timer, then the expiry time
is propagated into the timer pull hierarchy and the CPU makes sure
to wake up for the first pinned timer.
The timer pull hierarchy organizes CPUs in groups of eight at the
lowest level and at the next levels groups of eight groups up to the
point where no further aggregation of groups is required, i.e. the
number of levels is log8(NR_CPUS). The magic number of eight has been
established by experimention, but can be adjusted if needed.
In each group one busy CPU acts as the migrator. It's only one CPU to
avoid lock contention on remote timer wheels.
The migrator CPU checks in its own timer wheel handling whether there
are other CPUs in the group which have gone idle and have global timers
to expire. If there are global timers to expire, the migrator locks the
remote CPU timer wheel and handles the expiry.
Depending on the group level in the hierarchy this handling can require
to walk the hierarchy downwards to the CPU level.
Special care is taken when the last CPU goes idle. At this point the
CPU is the systemwide migrator at the top of the hierarchy and it
therefore cannot delegate to the hierarchy. It needs to arm its own
timer device to expire either at the first expiring timer in the
hierarchy or at the first CPU local timer, which ever expires first.
This completely removes the overhead from the enqueue path, which is
e.g. for networking a true hotpath and trades it for a slightly more
complex idle path.
This has been in development for a couple of years and the final series
has been extensively tested by various teams from silicon vendors and
ran through extensive CI.
There have been slight performance improvements observed on network
centric workloads and an Intel team confirmed that this allows them to
power down a die completely on a mult-die socket for the first time in
a mostly idle scenario.
There is only one outstanding ~1.5% regression on a specific overloaded
netperf test which is currently investigated, but the rest is either
positive or neutral performance wise and positive on the power
management side.
- Fixes for the timekeeping interpolation code for cross-timestamps:
cross-timestamps are used for PTP to get snapshots from hardware timers
and interpolated them back to clock MONOTONIC. The changes address a
few corner cases in the interpolation code which got the math and logic
wrong.
- Simplifcation of the clocksource watchdog retry logic to automatically
adjust to handle larger systems correctly instead of having more
incomprehensible command line parameters.
- Treewide consolidation of the VDSO data structures.
- The usual small improvements and cleanups all over the place.
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Merge tag 'timers-core-2024-03-10' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull timer updates from Thomas Gleixner:
"A large set of updates and features for timers and timekeeping:
- The hierarchical timer pull model
When timer wheel timers are armed they are placed into the timer
wheel of a CPU which is likely to be busy at the time of expiry.
This is done to avoid wakeups on potentially idle CPUs.
This is wrong in several aspects:
1) The heuristics to select the target CPU are wrong by
definition as the chance to get the prediction right is
close to zero.
2) Due to #1 it is possible that timers are accumulated on
a single target CPU
3) The required computation in the enqueue path is just overhead
for dubious value especially under the consideration that the
vast majority of timer wheel timers are either canceled or
rearmed before they expire.
The timer pull model avoids the above by removing the target
computation on enqueue and queueing timers always on the CPU on
which they get armed.
This is achieved by having separate wheels for CPU pinned timers
and global timers which do not care about where they expire.
As long as a CPU is busy it handles both the pinned and the global
timers which are queued on the CPU local timer wheels.
When a CPU goes idle it evaluates its own timer wheels:
- If the first expiring timer is a pinned timer, then the global
timers can be ignored as the CPU will wake up before they
expire.
- If the first expiring timer is a global timer, then the expiry
time is propagated into the timer pull hierarchy and the CPU
makes sure to wake up for the first pinned timer.
The timer pull hierarchy organizes CPUs in groups of eight at the
lowest level and at the next levels groups of eight groups up to
the point where no further aggregation of groups is required, i.e.
the number of levels is log8(NR_CPUS). The magic number of eight
has been established by experimention, but can be adjusted if
needed.
In each group one busy CPU acts as the migrator. It's only one CPU
to avoid lock contention on remote timer wheels.
The migrator CPU checks in its own timer wheel handling whether
there are other CPUs in the group which have gone idle and have
global timers to expire. If there are global timers to expire, the
migrator locks the remote CPU timer wheel and handles the expiry.
Depending on the group level in the hierarchy this handling can
require to walk the hierarchy downwards to the CPU level.
Special care is taken when the last CPU goes idle. At this point
the CPU is the systemwide migrator at the top of the hierarchy and
it therefore cannot delegate to the hierarchy. It needs to arm its
own timer device to expire either at the first expiring timer in
the hierarchy or at the first CPU local timer, which ever expires
first.
This completely removes the overhead from the enqueue path, which
is e.g. for networking a true hotpath and trades it for a slightly
more complex idle path.
This has been in development for a couple of years and the final
series has been extensively tested by various teams from silicon
vendors and ran through extensive CI.
There have been slight performance improvements observed on network
centric workloads and an Intel team confirmed that this allows them
to power down a die completely on a mult-die socket for the first
time in a mostly idle scenario.
There is only one outstanding ~1.5% regression on a specific
overloaded netperf test which is currently investigated, but the
rest is either positive or neutral performance wise and positive on
the power management side.
- Fixes for the timekeeping interpolation code for cross-timestamps:
cross-timestamps are used for PTP to get snapshots from hardware
timers and interpolated them back to clock MONOTONIC. The changes
address a few corner cases in the interpolation code which got the
math and logic wrong.
- Simplifcation of the clocksource watchdog retry logic to
automatically adjust to handle larger systems correctly instead of
having more incomprehensible command line parameters.
- Treewide consolidation of the VDSO data structures.
- The usual small improvements and cleanups all over the place"
* tag 'timers-core-2024-03-10' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (62 commits)
timer/migration: Fix quick check reporting late expiry
tick/sched: Fix build failure for CONFIG_NO_HZ_COMMON=n
vdso/datapage: Quick fix - use asm/page-def.h for ARM64
timers: Assert no next dyntick timer look-up while CPU is offline
tick: Assume timekeeping is correctly handed over upon last offline idle call
tick: Shut down low-res tick from dying CPU
tick: Split nohz and highres features from nohz_mode
tick: Move individual bit features to debuggable mask accesses
tick: Move got_idle_tick away from common flags
tick: Assume the tick can't be stopped in NOHZ_MODE_INACTIVE mode
tick: Move broadcast cancellation up to CPUHP_AP_TICK_DYING
tick: Move tick cancellation up to CPUHP_AP_TICK_DYING
tick: Start centralizing tick related CPU hotplug operations
tick/sched: Don't clear ts::next_tick again in can_stop_idle_tick()
tick/sched: Rename tick_nohz_stop_sched_tick() to tick_nohz_full_stop_tick()
tick: Use IS_ENABLED() whenever possible
tick/sched: Remove useless oneshot ifdeffery
tick/nohz: Remove duplicate between lowres and highres handlers
tick/nohz: Remove duplicate between tick_nohz_switch_to_nohz() and tick_setup_sched_timer()
hrtimer: Select housekeeping CPU during migration
...
|
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Peter Hilber
|
14274d0bd3 |
timekeeping: Fix cross-timestamp interpolation for non-x86
So far, get_device_system_crosststamp() unconditionally passes
system_counterval.cycles to timekeeping_cycles_to_ns(). But when
interpolating system time (do_interp == true), system_counterval.cycles is
before tkr_mono.cycle_last, contrary to the timekeeping_cycles_to_ns()
expectations.
On x86, CONFIG_CLOCKSOURCE_VALIDATE_LAST_CYCLE will mitigate on
interpolating, setting delta to 0. With delta == 0, xtstamp->sys_monoraw
and xtstamp->sys_realtime are then set to the last update time, as
implicitly expected by adjust_historical_crosststamp(). On other
architectures, the resulting nonsense xtstamp->sys_monoraw and
xtstamp->sys_realtime corrupt the xtstamp (ts) adjustment in
adjust_historical_crosststamp().
Fix this by deriving xtstamp->sys_monoraw and xtstamp->sys_realtime from
the last update time when interpolating, by using the local variable
"cycles". The local variable already has the right value when
interpolating, unlike system_counterval.cycles.
Fixes:
|
||
|
Peter Hilber
|
87a4113088 |
timekeeping: Fix cross-timestamp interpolation corner case decision
The cycle_between() helper checks if parameter test is in the open interval
(before, after). Colloquially speaking, this also applies to the counter
wrap-around special case before > after. get_device_system_crosststamp()
currently uses cycle_between() at the first call site to decide whether to
interpolate for older counter readings.
get_device_system_crosststamp() has the following problem with
cycle_between() testing against an open interval: Assume that, by chance,
cycles == tk->tkr_mono.cycle_last (in the following, "cycle_last" for
brevity). Then, cycle_between() at the first call site, with effective
argument values cycle_between(cycle_last, cycles, now), returns false,
enabling interpolation. During interpolation,
get_device_system_crosststamp() will then call cycle_between() at the
second call site (if a history_begin was supplied). The effective argument
values are cycle_between(history_begin->cycles, cycles, cycles), since
system_counterval.cycles == interval_start == cycles, per the assumption.
Due to the test against the open interval, cycle_between() returns false
again. This causes get_device_system_crosststamp() to return -EINVAL.
This failure should be avoided, since get_device_system_crosststamp() works
both when cycles follows cycle_last (no interpolation), and when cycles
precedes cycle_last (interpolation). For the case cycles == cycle_last,
interpolation is actually unneeded.
Fix this by changing cycle_between() into timestamp_in_interval(), which
now checks against the closed interval, rather than the open interval.
This changes the get_device_system_crosststamp() behavior for three corner
cases:
1. Bypass interpolation in the case cycles == tk->tkr_mono.cycle_last,
fixing the problem described above.
2. At the first timestamp_in_interval() call site, cycles == now no longer
causes failure.
3. At the second timestamp_in_interval() call site, history_begin->cycles
== system_counterval.cycles no longer causes failure.
adjust_historical_crosststamp() also works for this corner case,
where partial_history_cycles == total_history_cycles.
These behavioral changes should not cause any problems.
Fixes:
|
||
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Peter Hilber
|
84dccadd3e |
timekeeping: Fix cross-timestamp interpolation on counter wrap
cycle_between() decides whether get_device_system_crosststamp() will
interpolate for older counter readings.
cycle_between() yields wrong results for a counter wrap-around where after
< before < test, and for the case after < test < before.
Fix the comparison logic.
Fixes:
|
||
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Peter Hilber
|
4b7f521229 |
timekeeping: Evaluate system_counterval_t.cs_id instead of .cs
Clocksource pointers can be problematic to obtain for drivers which are not clocksource drivers themselves. In particular, the RFC virtio_rtc driver [1] would require a new helper function to obtain a pointer to the ARM Generic Timer clocksource. The ptp_kvm driver also required a similar workaround. Address this by evaluating the clocksource ID, rather than the clocksource pointer, of struct system_counterval_t. By this, setting the clocksource pointer becomes unneeded, and get_device_system_crosststamp() callers will no longer need to supply clocksource pointers. All relevant clocksource drivers provide the ID, so this change is not changing the behaviour. [1] https://lore.kernel.org/lkml/20231218073849.35294-1-peter.hilber@opensynergy.com/ Signed-off-by: Peter Hilber <peter.hilber@opensynergy.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Link: https://lore.kernel.org/r/20240201010453.2212371-7-peter.hilber@opensynergy.com |
||
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Peter Zijlstra
|
d16317de9b |
seqlock/latch: Provide raw_read_seqcount_latch_retry()
The read side of seqcount_latch consists of:
do {
seq = raw_read_seqcount_latch(&latch->seq);
...
} while (read_seqcount_latch_retry(&latch->seq, seq));
which is asymmetric in the raw_ department, and sure enough,
read_seqcount_latch_retry() includes (explicit) instrumentation where
raw_read_seqcount_latch() does not.
This inconsistency becomes a problem when trying to use it from
noinstr code. As such, fix it by renaming and re-implementing
raw_read_seqcount_latch_retry() without the instrumentation.
Specifically the instrumentation in question is kcsan_atomic_next(0)
in do___read_seqcount_retry(). Loosing this annotation is not a
problem because raw_read_seqcount_latch() does not pass through
kcsan_atomic_next(KCSAN_SEQLOCK_REGION_MAX).
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Tested-by: Michael Kelley <mikelley@microsoft.com> # Hyper-V
Link: https://lore.kernel.org/r/20230519102715.233598176@infradead.org
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||
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Geert Uytterhoeven
|
158009f1b4 |
timekeeping: Fix references to nonexistent ktime_get_fast_ns()
There was never a function named ktime_get_fast_ns().
Presumably these should refer to ktime_get_mono_fast_ns() instead.
Fixes:
|
||
|
Randy Dunlap
|
f3cb80804b |
time: Fix various kernel-doc problems
Clean up kernel-doc complaints about function names and non-kernel-doc comments in kernel/time/. Fixes these warnings: kernel/time/time.c:479: warning: expecting prototype for set_normalized_timespec(). Prototype was for set_normalized_timespec64() instead kernel/time/time.c:553: warning: expecting prototype for msecs_to_jiffies(). Prototype was for __msecs_to_jiffies() instead kernel/time/timekeeping.c:1595: warning: contents before sections kernel/time/timekeeping.c:1705: warning: This comment starts with '/**', but isn't a kernel-doc comment. * We have three kinds of time sources to use for sleep time kernel/time/timekeeping.c:1726: warning: This comment starts with '/**', but isn't a kernel-doc comment. * 1) can be determined whether to use or not only when doing kernel/time/tick-oneshot.c:21: warning: missing initial short description on line: * tick_program_event kernel/time/tick-oneshot.c:107: warning: expecting prototype for tick_check_oneshot_mode(). Prototype was for tick_oneshot_mode_active() instead Signed-off-by: Randy Dunlap <rdunlap@infradead.org> Signed-off-by: Ingo Molnar <mingo@kernel.org> Link: https://lore.kernel.org/r/20230103032849.12723-1-rdunlap@infradead.org |
||
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Jason A. Donenfeld
|
b8ac29b401 |
timekeeping: contribute wall clock to rng on time change
The rng's random_init() function contributes the real time to the rng at
boot time, so that events can at least start in relation to something
particular in the real world. But this clock might not yet be set that
point in boot, so nothing is contributed. In addition, the relation
between minor clock changes from, say, NTP, and the cycle counter is
potentially useful entropic data.
This commit addresses this by mixing in a time stamp on calls to
settimeofday and adjtimex. No entropy is credited in doing so, so it
doesn't make initialization faster, but it is still useful input to
have.
Fixes:
|
||
|
Linus Torvalds
|
ac2ab99072 |
Random number generator updates for Linux 5.19-rc1.
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Merge tag 'random-5.19-rc1-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/crng/random
Pull random number generator updates from Jason Donenfeld:
"These updates continue to refine the work began in 5.17 and 5.18 of
modernizing the RNG's crypto and streamlining and documenting its
code.
New for 5.19, the updates aim to improve entropy collection methods
and make some initial decisions regarding the "premature next" problem
and our threat model. The cloc utility now reports that random.c is
931 lines of code and 466 lines of comments, not that basic metrics
like that mean all that much, but at the very least it tells you that
this is very much a manageable driver now.
Here's a summary of the various updates:
- The random_get_entropy() function now always returns something at
least minimally useful. This is the primary entropy source in most
collectors, which in the best case expands to something like RDTSC,
but prior to this change, in the worst case it would just return 0,
contributing nothing. For 5.19, additional architectures are wired
up, and architectures that are entirely missing a cycle counter now
have a generic fallback path, which uses the highest resolution
clock available from the timekeeping subsystem.
Some of those clocks can actually be quite good, despite the CPU
not having a cycle counter of its own, and going off-core for a
stamp is generally thought to increase jitter, something positive
from the perspective of entropy gathering. Done very early on in
the development cycle, this has been sitting in next getting some
testing for a while now and has relevant acks from the archs, so it
should be pretty well tested and fine, but is nonetheless the thing
I'll be keeping my eye on most closely.
- Of particular note with the random_get_entropy() improvements is
MIPS, which, on CPUs that lack the c0 count register, will now
combine the high-speed but short-cycle c0 random register with the
lower-speed but long-cycle generic fallback path.
- With random_get_entropy() now always returning something useful,
the interrupt handler now collects entropy in a consistent
construction.
- Rather than comparing two samples of random_get_entropy() for the
jitter dance, the algorithm now tests many samples, and uses the
amount of differing ones to determine whether or not jitter entropy
is usable and how laborious it must be. The problem with comparing
only two samples was that if the cycle counter was extremely slow,
but just so happened to be on the cusp of a change, the slowness
wouldn't be detected. Taking many samples fixes that to some
degree.
This, combined with the other improvements to random_get_entropy(),
should make future unification of /dev/random and /dev/urandom
maybe more possible. At the very least, were we to attempt it again
today (we're not), it wouldn't break any of Guenter's test rigs
that broke when we tried it with 5.18. So, not today, but perhaps
down the road, that's something we can revisit.
- We attempt to reseed the RNG immediately upon waking up from system
suspend or hibernation, making use of the various timestamps about
suspend time and such available, as well as the usual inputs such
as RDRAND when available.
- Batched randomness now falls back to ordinary randomness before the
RNG is initialized. This provides more consistent guarantees to the
types of random numbers being returned by the various accessors.
- The "pre-init injection" code is now gone for good. I suspect you
in particular will be happy to read that, as I recall you
expressing your distaste for it a few months ago. Instead, to avoid
a "premature first" issue, while still allowing for maximal amount
of entropy availability during system boot, the first 128 bits of
estimated entropy are used immediately as it arrives, with the next
128 bits being buffered. And, as before, after the RNG has been
fully initialized, it winds up reseeding anyway a few seconds later
in most cases. This resulted in a pretty big simplification of the
initialization code and let us remove various ad-hoc mechanisms
like the ugly crng_pre_init_inject().
- The RNG no longer pretends to handle the "premature next" security
model, something that various academics and other RNG designs have
tried to care about in the past. After an interesting mailing list
thread, these issues are thought to be a) mainly academic and not
practical at all, and b) actively harming the real security of the
RNG by delaying new entropy additions after a potential compromise,
making a potentially bad situation even worse. As well, in the
first place, our RNG never even properly handled the premature next
issue, so removing an incomplete solution to a fake problem was
particularly nice.
This allowed for numerous other simplifications in the code, which
is a lot cleaner as a consequence. If you didn't see it before,
https://lore.kernel.org/lkml/YmlMGx6+uigkGiZ0@zx2c4.com/ may be a
thread worth skimming through.
- While the interrupt handler received a separate code path years ago
that avoids locks by using per-cpu data structures and a faster
mixing algorithm, in order to reduce interrupt latency, input and
disk events that are triggered in hardirq handlers were still
hitting locks and more expensive algorithms. Those are now
redirected to use the faster per-cpu data structures.
- Rather than having the fake-crypto almost-siphash-based random32
implementation be used right and left, and in many places where
cryptographically secure randomness is desirable, the batched
entropy code is now fast enough to replace that.
- As usual, numerous code quality and documentation cleanups. For
example, the initialization state machine now uses enum symbolic
constants instead of just hard coding numbers everywhere.
- Since the RNG initializes once, and then is always initialized
thereafter, a pretty heavy amount of code used during that
initialization is never used again. It is now completely cordoned
off using static branches and it winds up in the .text.unlikely
section so that it doesn't reduce cache compactness after the RNG
is ready.
- A variety of functions meant for waiting on the RNG to be
initialized were only used by vsprintf, and in not a particularly
optimal way. Replacing that usage with a more ordinary setup made
it possible to remove those functions.
- A cleanup of how we warn userspace about the use of uninitialized
/dev/urandom and uninitialized get_random_bytes() usage.
Interestingly, with the change you merged for 5.18 that attempts to
use jitter (but does not block if it can't), the majority of users
should never see those warnings for /dev/urandom at all now, and
the one for in-kernel usage is mainly a debug thing.
- The file_operations struct for /dev/[u]random now implements
.read_iter and .write_iter instead of .read and .write, allowing it
to also implement .splice_read and .splice_write, which makes
splice(2) work again after it was broken here (and in many other
places in the tree) during the set_fs() removal. This was a bit of
a last minute arrival from Jens that hasn't had as much time to
bake, so I'll be keeping my eye on this as well, but it seems
fairly ordinary. Unfortunately, read_iter() is around 3% slower
than read() in my tests, which I'm not thrilled about. But Jens and
Al, spurred by this observation, seem to be making progress in
removing the bottlenecks on the iter paths in the VFS layer in
general, which should remove the performance gap for all drivers.
- Assorted other bug fixes, cleanups, and optimizations.
- A small SipHash cleanup"
* tag 'random-5.19-rc1-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/crng/random: (49 commits)
random: check for signals after page of pool writes
random: wire up fops->splice_{read,write}_iter()
random: convert to using fops->write_iter()
random: convert to using fops->read_iter()
random: unify batched entropy implementations
random: move randomize_page() into mm where it belongs
random: remove mostly unused async readiness notifier
random: remove get_random_bytes_arch() and add rng_has_arch_random()
random: move initialization functions out of hot pages
random: make consistent use of buf and len
random: use proper return types on get_random_{int,long}_wait()
random: remove extern from functions in header
random: use static branch for crng_ready()
random: credit architectural init the exact amount
random: handle latent entropy and command line from random_init()
random: use proper jiffies comparison macro
random: remove ratelimiting for in-kernel unseeded randomness
random: move initialization out of reseeding hot path
random: avoid initializing twice in credit race
random: use symbolic constants for crng_init states
...
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|
Linus Torvalds
|
6e01f86fb2 |
Updates for timers and timekeeping core code:
- Expose CLOCK_TAI to instrumentation to aid with TSN debugging.
- Ensure that the clockevent is stopped when there is no timer armed to
avoid pointless wakeups.
- Make the sched clock frequency handling and rounding consistent.
- Provide a better debugobject hint for delayed works. The timer callback
is always the same, which makes it difficult to identify the underlying
work. Use the work function as a hint instead.
- Move the timer specific sysctl code into the timer subsystem.
- The usual set of improvements and cleanups
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Merge tag 'timers-core-2022-05-23' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull timer and timekeeping updates from Thomas Gleixner:
- Expose CLOCK_TAI to instrumentation to aid with TSN debugging.
- Ensure that the clockevent is stopped when there is no timer armed to
avoid pointless wakeups.
- Make the sched clock frequency handling and rounding consistent.
- Provide a better debugobject hint for delayed works. The timer
callback is always the same, which makes it difficult to identify the
underlying work. Use the work function as a hint instead.
- Move the timer specific sysctl code into the timer subsystem.
- The usual set of improvements and cleanups
* tag 'timers-core-2022-05-23' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
timers: Provide a better debugobjects hint for delayed works
time/sched_clock: Fix formatting of frequency reporting code
time/sched_clock: Use Hz as the unit for clock rate reporting below 4kHz
time/sched_clock: Round the frequency reported to nearest rather than down
timekeeping: Consolidate fast timekeeper
timekeeping: Annotate ktime_get_boot_fast_ns() with data_race()
timers/nohz: Switch to ONESHOT_STOPPED in the low-res handler when the tick is stopped
timekeeping: Introduce fast accessor to clock tai
tracing/timer: Add missing argument documentation of trace points
clocksource: Replace cpumask_weight() with cpumask_empty()
timers: Move timer sysctl into the timer code
clockevents: Use dedicated list iterator variable
timers: Simplify calc_index()
timers: Initialize base::next_expiry_recalc in timers_prepare_cpu()
|
||
|
Jason A. Donenfeld
|
1366992e16 |
timekeeping: Add raw clock fallback for random_get_entropy()
The addition of random_get_entropy_fallback() provides access to whichever time source has the highest frequency, which is useful for gathering entropy on platforms without available cycle counters. It's not necessarily as good as being able to quickly access a cycle counter that the CPU has, but it's still something, even when it falls back to being jiffies-based. In the event that a given arch does not define get_cycles(), falling back to the get_cycles() default implementation that returns 0 is really not the best we can do. Instead, at least calling random_get_entropy_fallback() would be preferable, because that always needs to return _something_, even falling back to jiffies eventually. It's not as though random_get_entropy_fallback() is super high precision or guaranteed to be entropic, but basically anything that's not zero all the time is better than returning zero all the time. Finally, since random_get_entropy_fallback() is used during extremely early boot when randomizing freelists in mm_init(), it can be called before timekeeping has been initialized. In that case there really is nothing we can do; jiffies hasn't even started ticking yet. So just give up and return 0. Suggested-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com> Reviewed-by: Thomas Gleixner <tglx@linutronix.de> Cc: Arnd Bergmann <arnd@arndb.de> Cc: Theodore Ts'o <tytso@mit.edu> |
||
|
Thomas Gleixner
|
90be8d6c1f |
timekeeping: Consolidate fast timekeeper
Provide a inline function which replaces the copy & pasta. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lore.kernel.org/r/20220415091921.072296632@linutronix.de |
||
|
Thomas Gleixner
|
eff4849f92 |
timekeeping: Annotate ktime_get_boot_fast_ns() with data_race()
Accessing timekeeper::offset_boot in ktime_get_boot_fast_ns() is an intended data race as the reader side cannot synchronize with a writer and there is no space in struct tk_read_base of the NMI safe timekeeper. Mark it so. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Link: https://lore.kernel.org/r/20220415091920.956045162@linutronix.de |
||
|
Kurt Kanzenbach
|
2c33d775ef |
timekeeping: Mark NMI safe time accessors as notrace
Mark the CLOCK_MONOTONIC fast time accessors as notrace. These functions are used in tracing to retrieve timestamps, so they should not recurse. Fixes: |
||
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Kurt Kanzenbach
|
3dc6ffae2d |
timekeeping: Introduce fast accessor to clock tai
Introduce fast/NMI safe accessor to clock tai for tracing. The Linux kernel tracing infrastructure has support for using different clocks to generate timestamps for trace events. Especially in TSN networks it's useful to have TAI as trace clock, because the application scheduling is done in accordance to the network time, which is based on TAI. With a tai trace_clock in place, it becomes very convenient to correlate network activity with Linux kernel application traces. Use the same implementation as ktime_get_boot_fast_ns() does by reading the monotonic time and adding the TAI offset. The same limitations as for the fast boot implementation apply. The TAI offset may change at run time e.g., by setting the time or using adjtimex() with an offset. However, these kind of offset changes are rare events. Nevertheless, the user has to be aware and deal with it in post processing. An alternative approach would be to use the same implementation as ktime_get_real_fast_ns() does. However, this requires to add an additional u64 member to the tk_read_base struct. This struct together with a seqcount is designed to fit into a single cache line on 64 bit architectures. Adding a new member would violate this constraint. Signed-off-by: Kurt Kanzenbach <kurt@linutronix.de> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: Steven Rostedt <rostedt@goodmis.org> Link: https://lore.kernel.org/r/20220414091805.89667-2-kurt@linutronix.de |
||
|
Yu Liao
|
4e8c11b6b3 |
timekeeping: Really make sure wall_to_monotonic isn't positive
Even after commit |
||
|
Thomas Gleixner
|
17a1b8826b |
hrtimer: Add bases argument to clock_was_set()
clock_was_set() unconditionaly invokes retrigger_next_event() on all online CPUs. This was necessary because that mechanism was also used for resume from suspend to idle which is not longer the case. The bases arguments allows the callers of clock_was_set() to hand in a mask which tells clock_was_set() which of the hrtimer clock bases are affected by the clock setting. This mask will be used in the next step to check whether a CPU base has timers queued on a clock base affected by the event and avoid the SMP function call if there are none. Add a @bases argument, provide defines for the active bases masking and fixup all callsites. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Link: https://lore.kernel.org/r/20210713135158.691083465@linutronix.de |
||
|
Thomas Gleixner
|
1b267793f4 |
time/timekeeping: Avoid invoking clock_was_set() twice
do_adjtimex() might end up scheduling a delayed clock_was_set() via timekeeping_advance() and then invoke clock_was_set() directly which is pointless. Make timekeeping_advance() return whether an invocation of clock_was_set() is required and handle it at the call sites which allows do_adjtimex() to issue a single direct call if required. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Link: https://lore.kernel.org/r/20210713135158.580966888@linutronix.de |
||
|
Thomas Gleixner
|
a761a67f59 |
timekeeping: Distangle resume and clock-was-set events
Resuming timekeeping is a clock-was-set event and uses the clock-was-set notification mechanism. This is in the way of making the clock-was-set update for hrtimers selective so unnecessary IPIs are avoided when a CPU base does not have timers queued which are affected by the clock setting. Distangle it by invoking hrtimer_resume() on each unfreezing CPU and invoke the new timerfd_resume() function from timekeeping_resume() which is the only place where this is needed. Rename hrtimer_resume() to hrtimer_resume_local() to reflect the change. With this the clock_was_set*() functions are not longer required to IPI all CPUs unconditionally and can get some smarts to avoid them. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Link: https://lore.kernel.org/r/20210713135158.488853478@linutronix.de |
||
|
Linus Torvalds
|
152d32aa84 |
ARM:
- Stage-2 isolation for the host kernel when running in protected mode
- Guest SVE support when running in nVHE mode
- Force W^X hypervisor mappings in nVHE mode
- ITS save/restore for guests using direct injection with GICv4.1
- nVHE panics now produce readable backtraces
- Guest support for PTP using the ptp_kvm driver
- Performance improvements in the S2 fault handler
x86:
- Optimizations and cleanup of nested SVM code
- AMD: Support for virtual SPEC_CTRL
- Optimizations of the new MMU code: fast invalidation,
zap under read lock, enable/disably dirty page logging under
read lock
- /dev/kvm API for AMD SEV live migration (guest API coming soon)
- support SEV virtual machines sharing the same encryption context
- support SGX in virtual machines
- add a few more statistics
- improved directed yield heuristics
- Lots and lots of cleanups
Generic:
- Rework of MMU notifier interface, simplifying and optimizing
the architecture-specific code
- Some selftests improvements
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Merge tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm
Pull kvm updates from Paolo Bonzini:
"This is a large update by KVM standards, including AMD PSP (Platform
Security Processor, aka "AMD Secure Technology") and ARM CoreSight
(debug and trace) changes.
ARM:
- CoreSight: Add support for ETE and TRBE
- Stage-2 isolation for the host kernel when running in protected
mode
- Guest SVE support when running in nVHE mode
- Force W^X hypervisor mappings in nVHE mode
- ITS save/restore for guests using direct injection with GICv4.1
- nVHE panics now produce readable backtraces
- Guest support for PTP using the ptp_kvm driver
- Performance improvements in the S2 fault handler
x86:
- AMD PSP driver changes
- Optimizations and cleanup of nested SVM code
- AMD: Support for virtual SPEC_CTRL
- Optimizations of the new MMU code: fast invalidation, zap under
read lock, enable/disably dirty page logging under read lock
- /dev/kvm API for AMD SEV live migration (guest API coming soon)
- support SEV virtual machines sharing the same encryption context
- support SGX in virtual machines
- add a few more statistics
- improved directed yield heuristics
- Lots and lots of cleanups
Generic:
- Rework of MMU notifier interface, simplifying and optimizing the
architecture-specific code
- a handful of "Get rid of oprofile leftovers" patches
- Some selftests improvements"
* tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm: (379 commits)
KVM: selftests: Speed up set_memory_region_test
selftests: kvm: Fix the check of return value
KVM: x86: Take advantage of kvm_arch_dy_has_pending_interrupt()
KVM: SVM: Skip SEV cache flush if no ASIDs have been used
KVM: SVM: Remove an unnecessary prototype declaration of sev_flush_asids()
KVM: SVM: Drop redundant svm_sev_enabled() helper
KVM: SVM: Move SEV VMCB tracking allocation to sev.c
KVM: SVM: Explicitly check max SEV ASID during sev_hardware_setup()
KVM: SVM: Unconditionally invoke sev_hardware_teardown()
KVM: SVM: Enable SEV/SEV-ES functionality by default (when supported)
KVM: SVM: Condition sev_enabled and sev_es_enabled on CONFIG_KVM_AMD_SEV=y
KVM: SVM: Append "_enabled" to module-scoped SEV/SEV-ES control variables
KVM: SEV: Mask CPUID[0x8000001F].eax according to supported features
KVM: SVM: Move SEV module params/variables to sev.c
KVM: SVM: Disable SEV/SEV-ES if NPT is disabled
KVM: SVM: Free sev_asid_bitmap during init if SEV setup fails
KVM: SVM: Zero out the VMCB array used to track SEV ASID association
x86/sev: Drop redundant and potentially misleading 'sev_enabled'
KVM: x86: Move reverse CPUID helpers to separate header file
KVM: x86: Rename GPR accessors to make mode-aware variants the defaults
...
|
||
|
Thomas Gleixner
|
b2c67cbe9f |
time: Add mechanism to recognize clocksource in time_get_snapshot
System time snapshots are not conveying information about the current clocksource which was used, but callers like the PTP KVM guest implementation have the requirement to evaluate the clocksource type to select the appropriate mechanism. Introduce a clocksource id field in struct clocksource which is by default set to CSID_GENERIC (0). Clocksource implementations can set that field to a value which allows to identify the clocksource. Store the clocksource id of the current clocksource in the system_time_snapshot so callers can evaluate which clocksource was used to take the snapshot and act accordingly. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Jianyong Wu <jianyong.wu@arm.com> Signed-off-by: Marc Zyngier <maz@kernel.org> Link: https://lore.kernel.org/r/20201209060932.212364-5-jianyong.wu@arm.com |
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|
Niklas Söderlund
|
d4c7c28806 |
timekeeping: Allow runtime PM from change_clocksource()
The struct clocksource callbacks enable() and disable() are described as a
way to allow clock sources to enter a power save mode. See commit
|
||
|
Ingo Molnar
|
4bf07f6562 |
timekeeping, clocksource: Fix various typos in comments
Fix ~56 single-word typos in timekeeping & clocksource code comments. Signed-off-by: Ingo Molnar <mingo@kernel.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: John Stultz <john.stultz@linaro.org> Cc: Stephen Boyd <sboyd@kernel.org> Cc: Daniel Lezcano <daniel.lezcano@linaro.org> Cc: linux-kernel@vger.kernel.org |
||
|
Chunguang Xu
|
aba428a0c6 |
timekeeping: Remove unused get_seconds()
The get_seconds() cleanup seems to have been completed, now it is time to delete the legacy interface to avoid misuse later. Signed-off-by: Chunguang Xu <brookxu@tencent.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Link: https://lore.kernel.org/r/1606816351-26900-1-git-send-email-brookxu@tencent.com |
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|
Linus Torvalds
|
7a932e5702 |
asm-generic: cross-architecture timer cleanup
This cleans up two ancient timer features that were never completed in the past, CONFIG_GENERIC_CLOCKEVENTS and CONFIG_ARCH_USES_GETTIMEOFFSET. There was only one user left for the ARCH_USES_GETTIMEOFFSET variant of clocksource implementations, the ARM EBSA110 platform. Rather than changing to use modern timekeeping, we remove the platform entirely as Russell no longer uses his machine and nobody else seems to have one any more. The conditional code for using arch_gettimeoffset() is removed as a result. For CONFIG_GENERIC_CLOCKEVENTS, there are still a couple of platforms not using clockevent drivers: parisc, ia64, most of m68k, and one Arm platform. These all do timer ticks slighly differently, and this gets cleaned up to the point they at least all call the same helper function. Instead of most platforms using 'select GENERIC_CLOCKEVENTS' in Kconfig, the polarity is now reversed, with the few remaining ones selecting LEGACY_TIMER_TICK instead. Signed-off-by: Arnd Bergmann <arnd@arndb.de> -----BEGIN PGP SIGNATURE----- iQIzBAABCgAdFiEEo6/YBQwIrVS28WGKmmx57+YAGNkFAl/Y1v8ACgkQmmx57+YA GNmCvQ/9EDlgCt92r8SB+LGafDtgB8TUQZeIrs9S2mByzdxwnw0lxObIXFCnhQgh RpG3dR+ONRDnC5eI149B377JOEFMZWe2+BtYHUHkFARtUEWatslQcz7yAGvVRK/l TS/qReb6piKltlzuanF1bMZbjy2OhlaDRcm+OlC3y5mALR33M4emb+rJ6cSdfk3K v1iZhrxtfQT77ztesh/oPkPiyQ6kNcz7SfpyYOb6f5VLlml2BZ7YwBSVyGY7urHk RL3XqOUP4KKlMEAI8w0E2nvft6Fk+luziBhrMYWK0GvbmI1OESENuX/c6tgT2OQ1 DRaVHvcPG/EAY8adOKxxVyHhEJDSoz5GJV/EtjlOegsJk6RomczR1uuiT3Kvm7Ah PktMKv4xQht1E15KPSKbOvNIEP18w2s5z6gw+jVDv8pw42pVEQManm1D+BICqrhl fcpw6T1drf9UxAjwX4+zXtmNs+a+mqiFG8puU4VVgT4GpQ8umHvunXz2WUjZO0jc 3m8ErJHBvtJwW5TOHGyXnjl9SkwPzHOfF6IcXTYWEDU4/gQIK9TwUvCjLc0lE27t FMCV2ds7/K1CXwRgpa5IrefSkb8yOXSbRZ56NqqF7Ekxw4J5bYRSaY7jb+qD/e+3 5O1y+iPxFrpH+16hSahvzrtcdFNbLQvBBuRtEQOYuHLt2UJrNoU= =QpNs -----END PGP SIGNATURE----- Merge tag 'asm-generic-timers-5.11' of git://git.kernel.org/pub/scm/linux/kernel/git/arnd/asm-generic Pull asm-generic cross-architecture timer cleanup from Arnd Bergmann: "This cleans up two ancient timer features that were never completed in the past, CONFIG_GENERIC_CLOCKEVENTS and CONFIG_ARCH_USES_GETTIMEOFFSET. There was only one user left for the ARCH_USES_GETTIMEOFFSET variant of clocksource implementations, the ARM EBSA110 platform. Rather than changing to use modern timekeeping, we remove the platform entirely as Russell no longer uses his machine and nobody else seems to have one any more. The conditional code for using arch_gettimeoffset() is removed as a result. For CONFIG_GENERIC_CLOCKEVENTS, there are still a couple of platforms not using clockevent drivers: parisc, ia64, most of m68k, and one Arm platform. These all do timer ticks slighly differently, and this gets cleaned up to the point they at least all call the same helper function. Instead of most platforms using 'select GENERIC_CLOCKEVENTS' in Kconfig, the polarity is now reversed, with the few remaining ones selecting LEGACY_TIMER_TICK instead" * tag 'asm-generic-timers-5.11' of git://git.kernel.org/pub/scm/linux/kernel/git/arnd/asm-generic: timekeeping: default GENERIC_CLOCKEVENTS to enabled timekeeping: remove xtime_update m68k: remove timer_interrupt() function m68k: change remaining timers to legacy_timer_tick m68k: m68328: use legacy_timer_tick() m68k: sun3/sun3c: use legacy_timer_tick m68k: split heartbeat out of timer function m68k: coldfire: use legacy_timer_tick() parisc: use legacy_timer_tick ARM: rpc: use legacy_timer_tick ia64: convert to legacy_timer_tick timekeeping: add CONFIG_LEGACY_TIMER_TICK timekeeping: remove arch_gettimeoffset net: remove am79c961a driver ARM: remove ebsa110 platform |
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|
Alex Shi
|
6e5a91901c |
timekeeping: Address parameter documentation issues for various functions
The kernel-doc parser complains: kernel/time/timekeeping.c:1543: warning: Function parameter or member 'ts' not described in 'read_persistent_clock64' kernel/time/timekeeping.c:764: warning: Function parameter or member 'tk' not described in 'timekeeping_forward_now' kernel/time/timekeeping.c:1331: warning: Function parameter or member 'ts' not described in 'timekeeping_inject_offset' kernel/time/timekeeping.c:1331: warning: Excess function parameter 'tv' description in 'timekeeping_inject_offset' Add the missing parameter documentations and rename the 'tv' parameter of timekeeping_inject_offset() to 'ts' so it matches the implemention. [ tglx: Reworded a few docs and massaged changelog ] Signed-off-by: Alex Shi <alex.shi@linux.alibaba.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Link: https://lore.kernel.org/r/1605252275-63652-5-git-send-email-alex.shi@linux.alibaba.com |
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Alex Shi
|
29efc4612a |
timekeeping: Fix parameter docs of read_persistent_wall_and_boot_offset()
Address the following kernel-doc markup warnings: kernel/time/timekeeping.c:1563: warning: Function parameter or member 'wall_time' not described in 'read_persistent_wall_and_boot_offset' kernel/time/timekeeping.c:1563: warning: Function parameter or member 'boot_offset' not described in 'read_persistent_wall_and_boot_offset' The parameters are described but miss the leading '@' and the colon after the parameter names. [ tglx: Massaged changelog ] Signed-off-by: Alex Shi <alex.shi@linux.alibaba.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Link: https://lore.kernel.org/r/1605252275-63652-6-git-send-email-alex.shi@linux.alibaba.com |
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Alex Shi
|
f27f7c3f10 |
timekeeping: Add missing parameter docs for pvclock_gtod_[un]register_notifier()
The kernel-doc parser complains about: kernel/time/timekeeping.c:651: warning: Function parameter or member 'nb' not described in 'pvclock_gtod_register_notifier' kernel/time/timekeeping.c:670: warning: Function parameter or member 'nb' not described in 'pvclock_gtod_unregister_notifier' Add the missing parameter explanations. [ tglx: Massaged changelog ] Signed-off-by: Alex Shi <alex.shi@linux.alibaba.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Link: https://lore.kernel.org/r/1605252275-63652-3-git-send-email-alex.shi@linux.alibaba.com |
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Thomas Gleixner
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c1ce406e80 |
timekeeping: Fix up function documentation for the NMI safe accessors
Alex reported the following warning: kernel/time/timekeeping.c:464: warning: Function parameter or member 'tkf' not described in '__ktime_get_fast_ns' which is not entirely correct because the documented function is ktime_get_mono_fast_ns() which does not have a parameter, but the kernel-doc parser looks at the function declaration which follows the comment and complains about the missing parameter documentation. Aside of that the documentation for the rest of the NMI safe accessors is either incomplete or missing. - Move the function documentation to the right place - Fixup the references and inconsistencies - Add the missing documentation for ktime_get_raw_fast_ns() Reported-by: Alex Shi <alex.shi@linux.alibaba.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> |
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Alex Shi
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e025b03113 |
timekeeping: Add missing parameter documentation for update_fast_timekeeper()
Address the following warning: kernel/time/timekeeping.c:415: warning: Function parameter or member 'tkf' not described in 'update_fast_timekeeper' [ tglx: Remove the bogus ktime_get_mono_fast_ns() part ] Signed-off-by: Alex Shi <alex.shi@linux.alibaba.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Link: https://lore.kernel.org/r/1605252275-63652-2-git-send-email-alex.shi@linux.alibaba.com |
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Alex Shi
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199d280c88 |
timekeeping: Remove static functions from kernel-doc markup
Various static functions in the timekeeping code have function comments which pretend to be kernel-doc, but are incomplete and trigger parser warnings. As these functions are local to the timekeeping core code there is no need to expose them via kernel-doc. Remove the double star kernel-doc marker and remove excess newlines. [ tglx: Massaged changelog and removed excess newlines ] Signed-off-by: Alex Shi <alex.shi@linux.alibaba.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Link: https://lore.kernel.org/r/1605252275-63652-4-git-send-email-alex.shi@linux.alibaba.com |
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Arnd Bergmann
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56cc7b8acf |
timekeeping: remove xtime_update
There are no more users of xtime_update aside from legacy_timer_tick(), so fold it into that function and remove the declaration. update_process_times() is now only called inside of the kernel/time/ code, so the declaration can be moved there. Reviewed-by: Geert Uytterhoeven <geert@linux-m68k.org> Tested-by: Geert Uytterhoeven <geert@linux-m68k.org> Reviewed-by: Linus Walleij <linus.walleij@linaro.org> Signed-off-by: Arnd Bergmann <arnd@arndb.de> |
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Arnd Bergmann
|
77f6c0b874 |
timekeeping: remove arch_gettimeoffset
With Arm EBSA110 gone, nothing uses it any more, so the corresponding code and the Kconfig option can be removed. Acked-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Linus Walleij <linus.walleij@linaro.org> Signed-off-by: Arnd Bergmann <arnd@arndb.de> |
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Linus Torvalds
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ed016af52e |
These are the locking updates for v5.10:
- Add deadlock detection for recursive read-locks. The rationale is outlined
in:
|
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Ahmed S. Darwish
|
249d053835 |
timekeeping: Use seqcount_latch_t
Latch sequence counters are a multiversion concurrency control mechanism where the seqcount_t counter even/odd value is used to switch between two data storage copies. This allows the seqcount_t read path to safely interrupt its write side critical section (e.g. from NMIs). Initially, latch sequence counters were implemented as a single write function, raw_write_seqcount_latch(), above plain seqcount_t. The read path was expected to use plain seqcount_t raw_read_seqcount(). A specialized read function was later added, raw_read_seqcount_latch(), and became the standardized way for latch read paths. Having unique read and write APIs meant that latch sequence counters are basically a data type of their own -- just inappropriately overloading plain seqcount_t. The seqcount_latch_t data type was thus introduced at seqlock.h. Use that new data type instead of seqcount_raw_spinlock_t. This ensures that only latch-safe APIs are to be used with the sequence counter. Note that the use of seqcount_raw_spinlock_t was not very useful in the first place. Only the "raw_" subset of seqcount_t APIs were used at timekeeping.c. This subset was created for contexts where lockdep cannot be used. seqcount_LOCKTYPE_t's raison d'être -- verifying that the seqcount_t writer serialization lock is held -- cannot thus be done. References: |
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Thomas Gleixner
|
e2d977c9f1 |
timekeeping: Provide multi-timestamp accessor to NMI safe timekeeper
printk wants to store various timestamps (MONOTONIC, REALTIME, BOOTTIME) to
make correlation of dmesg from several systems easier.
Provide an interface to retrieve all three timestamps in one go.
There are some caveats:
1) Boot time and late sleep time injection
Boot time is a racy access on 32bit systems if the sleep time injection
happens late during resume and not in timekeeping_resume(). That could be
avoided by expanding struct tk_read_base with boot offset for 32bit and
adding more overhead to the update. As this is a hard to observe once per
resume event which can be filtered with reasonable effort using the
accurate mono/real timestamps, it's probably not worth the trouble.
Aside of that it might be possible on 32 and 64 bit to observe the
following when the sleep time injection happens late:
CPU 0 CPU 1
timekeeping_resume()
ktime_get_fast_timestamps()
mono, real = __ktime_get_real_fast()
inject_sleep_time()
update boot offset
boot = mono + bootoffset;
That means that boot time already has the sleep time adjustment, but
real time does not. On the next readout both are in sync again.
Preventing this for 64bit is not really feasible without destroying the
careful cache layout of the timekeeper because the sequence count and
struct tk_read_base would then need two cache lines instead of one.
2) Suspend/resume timestamps
Access to the time keeper clock source is disabled accross the innermost
steps of suspend/resume. The accessors still work, but the timestamps
are frozen until time keeping is resumed which happens very early.
For regular suspend/resume there is no observable difference vs. sched
clock, but it might affect some of the nasty low level debug printks.
OTOH, access to sched clock is not guaranteed accross suspend/resume on
all systems either so it depends on the hardware in use.
If that turns out to be a real problem then this could be mitigated by
using sched clock in a similar way as during early boot. But it's not as
trivial as on early boot because it needs some careful protection
against the clock monotonic timestamp jumping backwards on resume.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20200814115512.159981360@linutronix.de
|
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Thomas Gleixner
|
71419b30ca |
timekeeping: Utilize local_clock() for NMI safe timekeeper during early boot
During early boot the NMI safe timekeeper returns 0 until the first clocksource becomes available. This prevents it from being used for printk or other facilities which today use sched clock. sched clock can be available way before timekeeping is initialized. The obvious workaround for this is to utilize the early sched clock in the default dummy clock read function until a clocksource becomes available. After switching to the clocksource clock MONOTONIC and BOOTTIME will not jump because the timekeeping_init() bases clock MONOTONIC on sched clock and the offset between clock MONOTONIC and BOOTTIME is zero during boot. Clock REALTIME cannot provide useful timestamps during early boot up to the point where a persistent clock becomes available, which is either in timekeeping_init() or later when the RTC driver which might depend on I2C or other subsystems is initialized. There is a minor difference to sched_clock() vs. suspend/resume. As the timekeeper clock source might not be accessible during suspend, after timekeeping_suspend() timestamps freeze up to the point where timekeeping_resume() is invoked. OTOH this is true for some sched clock implementations as well. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Tested-by: Petr Mladek <pmladek@suse.com> Link: https://lore.kernel.org/r/20200814115512.041422402@linutronix.de |
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|
Linus Torvalds
|
b923f1247b |
A set oftimekeeping/VDSO updates:
- Preparatory work to allow S390 to switch over to the generic VDSO
implementation.
S390 requires that the VDSO data pointer is handed in to the counter
read function when time namespace support is enabled. Adding the pointer
is a NOOP for all other architectures because the compiler is supposed
to optimize that out when it is unused in the architecture specific
inline. The change also solved a similar problem for MIPS which
fortunately has time namespaces not yet enabled.
S390 needs to update clock related VDSO data independent of the
timekeeping updates. This was solved so far with yet another sequence
counter in the S390 implementation. A better solution is to utilize the
already existing VDSO sequence count for this. The core code now exposes
helper functions which allow to serialize against the timekeeper code
and against concurrent readers.
S390 needs extra data for their clock readout function. The initial
common VDSO data structure did not provide a way to add that. It now has
an embedded architecture specific struct embedded which defaults to an
empty struct.
Doing this now avoids tree dependencies and conflicts post rc1 and
allows all other architectures which work on generic VDSO support to
work from a common upstream base.
- A trivial comment fix.
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Merge tag 'timers-urgent-2020-08-14' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull timekeeping updates from Thomas Gleixner:
"A set of timekeeping/VDSO updates:
- Preparatory work to allow S390 to switch over to the generic VDSO
implementation.
S390 requires that the VDSO data pointer is handed in to the
counter read function when time namespace support is enabled.
Adding the pointer is a NOOP for all other architectures because
the compiler is supposed to optimize that out when it is unused in
the architecture specific inline. The change also solved a similar
problem for MIPS which fortunately has time namespaces not yet
enabled.
S390 needs to update clock related VDSO data independent of the
timekeeping updates. This was solved so far with yet another
sequence counter in the S390 implementation. A better solution is
to utilize the already existing VDSO sequence count for this. The
core code now exposes helper functions which allow to serialize
against the timekeeper code and against concurrent readers.
S390 needs extra data for their clock readout function. The initial
common VDSO data structure did not provide a way to add that. It
now has an embedded architecture specific struct embedded which
defaults to an empty struct.
Doing this now avoids tree dependencies and conflicts post rc1 and
allows all other architectures which work on generic VDSO support
to work from a common upstream base.
- A trivial comment fix"
* tag 'timers-urgent-2020-08-14' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
time: Delete repeated words in comments
lib/vdso: Allow to add architecture-specific vdso data
timekeeping/vsyscall: Provide vdso_update_begin/end()
vdso/treewide: Add vdso_data pointer argument to __arch_get_hw_counter()
|
||
|
Linus Torvalds
|
97d052ea3f |
A set of locking fixes and updates:
- Untangle the header spaghetti which causes build failures in various
situations caused by the lockdep additions to seqcount to validate that
the write side critical sections are non-preemptible.
- The seqcount associated lock debug addons which were blocked by the
above fallout.
seqcount writers contrary to seqlock writers must be externally
serialized, which usually happens via locking - except for strict per
CPU seqcounts. As the lock is not part of the seqcount, lockdep cannot
validate that the lock is held.
This new debug mechanism adds the concept of associated locks.
sequence count has now lock type variants and corresponding
initializers which take a pointer to the associated lock used for
writer serialization. If lockdep is enabled the pointer is stored and
write_seqcount_begin() has a lockdep assertion to validate that the
lock is held.
Aside of the type and the initializer no other code changes are
required at the seqcount usage sites. The rest of the seqcount API is
unchanged and determines the type at compile time with the help of
_Generic which is possible now that the minimal GCC version has been
moved up.
Adding this lockdep coverage unearthed a handful of seqcount bugs which
have been addressed already independent of this.
While generaly useful this comes with a Trojan Horse twist: On RT
kernels the write side critical section can become preemtible if the
writers are serialized by an associated lock, which leads to the well
known reader preempts writer livelock. RT prevents this by storing the
associated lock pointer independent of lockdep in the seqcount and
changing the reader side to block on the lock when a reader detects
that a writer is in the write side critical section.
- Conversion of seqcount usage sites to associated types and initializers.
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Merge tag 'locking-urgent-2020-08-10' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull locking updates from Thomas Gleixner:
"A set of locking fixes and updates:
- Untangle the header spaghetti which causes build failures in
various situations caused by the lockdep additions to seqcount to
validate that the write side critical sections are non-preemptible.
- The seqcount associated lock debug addons which were blocked by the
above fallout.
seqcount writers contrary to seqlock writers must be externally
serialized, which usually happens via locking - except for strict
per CPU seqcounts. As the lock is not part of the seqcount, lockdep
cannot validate that the lock is held.
This new debug mechanism adds the concept of associated locks.
sequence count has now lock type variants and corresponding
initializers which take a pointer to the associated lock used for
writer serialization. If lockdep is enabled the pointer is stored
and write_seqcount_begin() has a lockdep assertion to validate that
the lock is held.
Aside of the type and the initializer no other code changes are
required at the seqcount usage sites. The rest of the seqcount API
is unchanged and determines the type at compile time with the help
of _Generic which is possible now that the minimal GCC version has
been moved up.
Adding this lockdep coverage unearthed a handful of seqcount bugs
which have been addressed already independent of this.
While generally useful this comes with a Trojan Horse twist: On RT
kernels the write side critical section can become preemtible if
the writers are serialized by an associated lock, which leads to
the well known reader preempts writer livelock. RT prevents this by
storing the associated lock pointer independent of lockdep in the
seqcount and changing the reader side to block on the lock when a
reader detects that a writer is in the write side critical section.
- Conversion of seqcount usage sites to associated types and
initializers"
* tag 'locking-urgent-2020-08-10' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (25 commits)
locking/seqlock, headers: Untangle the spaghetti monster
locking, arch/ia64: Reduce <asm/smp.h> header dependencies by moving XTP bits into the new <asm/xtp.h> header
x86/headers: Remove APIC headers from <asm/smp.h>
seqcount: More consistent seqprop names
seqcount: Compress SEQCNT_LOCKNAME_ZERO()
seqlock: Fold seqcount_LOCKNAME_init() definition
seqlock: Fold seqcount_LOCKNAME_t definition
seqlock: s/__SEQ_LOCKDEP/__SEQ_LOCK/g
hrtimer: Use sequence counter with associated raw spinlock
kvm/eventfd: Use sequence counter with associated spinlock
userfaultfd: Use sequence counter with associated spinlock
NFSv4: Use sequence counter with associated spinlock
iocost: Use sequence counter with associated spinlock
raid5: Use sequence counter with associated spinlock
vfs: Use sequence counter with associated spinlock
timekeeping: Use sequence counter with associated raw spinlock
xfrm: policy: Use sequence counters with associated lock
netfilter: nft_set_rbtree: Use sequence counter with associated rwlock
netfilter: conntrack: Use sequence counter with associated spinlock
sched: tasks: Use sequence counter with associated spinlock
...
|