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Merge pull request #1319 from brauner/2016-11-25/fix_logging_race

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log: fix race
This commit is contained in:
Stéphane Graber 2016-11-25 18:20:25 -05:00 committed by GitHub
commit 1145b82876
2 changed files with 62 additions and 26 deletions
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2
configure.ac
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@ -628,7 +628,7 @@ AC_CHECK_DECLS([PR_GET_NO_NEW_PRIVS], [], [], [#include <sys/prctl.h>])
AC_CHECK_HEADERS([sys/signalfd.h pty.h ifaddrs.h sys/capability.h sys/personality.h utmpx.h sys/timerfd.h])
# Check for some syscalls functions
AC_CHECK_FUNCS([setns pivot_root sethostname unshare rand_r confstr faccessat])
AC_CHECK_FUNCS([setns pivot_root sethostname unshare rand_r confstr faccessat gettid])
# Check for some functions
AC_CHECK_LIB(pthread, main)

86
src/lxc/log.c
View File

@ -45,6 +45,20 @@
#define LXC_LOG_DATEFOMAT_SIZE 15
#ifndef HAVE_GETTID
static inline pid_t gettid(void)
{
#ifdef __NR_gettid
return (pid_t)syscall(SYS_gettid);
#else
errno = ENOSYS;
return -1;
#endif
}
#else
extern pid_t gettid(void);
#endif
int lxc_log_fd = -1;
static int syslog_enable = 0;
int lxc_quiet_specified;
@ -137,11 +151,11 @@ static int log_append_stderr(const struct lxc_log_appender *appender,
static int log_append_logfile(const struct lxc_log_appender *appender,
struct lxc_log_event *event)
{
char date[LXC_LOG_DATEFOMAT_SIZE] = "20150427012246";
char date[LXC_LOG_DATEFOMAT_SIZE] = "N/A";
char buffer[LXC_LOG_BUFFER_SIZE];
struct tm newtime;
int n;
int ms;
int ms = 0;
int fd_to_use = -1;
#ifndef NO_LXC_CONF
@ -155,34 +169,56 @@ static int log_append_logfile(const struct lxc_log_appender *appender,
if (fd_to_use == -1)
return 0;
if (!localtime_r(&event->timestamp.tv_sec, &newtime))
return 0;
strftime(date, sizeof(date), "%Y%m%d%H%M%S", &newtime);
ms = event->timestamp.tv_usec / 1000;
n = snprintf(buffer, sizeof(buffer),
"%15s%s%s %10s.%03d %-8s %s - %s:%s:%d - ",
log_prefix,
log_vmname ? " " : "",
log_vmname ? log_vmname : "",
date,
ms,
lxc_log_priority_to_string(event->priority),
event->category,
event->locinfo->file, event->locinfo->func,
event->locinfo->line);
/* localtime_r() can lead to deadlocks when LXC is used multithreaded
* because it calls __tzset() and __tzconvert() internally. The deadlock
* stems from an interaction between these functions and the functions
* in monitor.c and commands.{c,h}. Some of the latter functions will
* write to the log independent of the container thread that is
* currently running. Since the monitor fork()ed it seems to duplicate
* the mutex states of the time functions mentioned above.
* As a short term fix, I suggest to simply disable receiving the time
* when these monitor.c or command.{c,h} functions are called. This
* should be ok, since the [lxc monitor] will only emit a few messages
* and thread-safety is currently more important than beautiful logs.
* The rest of the log stays the same as it was before.
*/
if (getpid() == gettid()) {
if (!localtime_r(&event->timestamp.tv_sec, &newtime))
return 0;
strftime(date, sizeof(date), "%Y%m%d%H%M%S", &newtime);
ms = event->timestamp.tv_usec / 1000;
n = snprintf(buffer, sizeof(buffer),
"%15s%s%s %14s.%03d %-8s %s - %s:%s:%d - ",
log_prefix,
log_vmname ? " " : "",
log_vmname ? log_vmname : "",
date,
ms,
lxc_log_priority_to_string(event->priority),
event->category,
event->locinfo->file, event->locinfo->func,
event->locinfo->line);
} else {
n = snprintf(buffer, sizeof(buffer),
"%15s%s%s %-14s %3s %-8s %s - %s:%s:%d - ",
log_prefix,
log_vmname ? " " : "",
log_vmname ? log_vmname : "",
date,
"",
lxc_log_priority_to_string(event->priority),
event->category,
event->locinfo->file, event->locinfo->func,
event->locinfo->line);
}
if (n < 0)
return n;
if (n < sizeof(buffer) - 1)
n += vsnprintf(buffer + n, sizeof(buffer) - n, event->fmt,
*event->vap);
else {
WARN("truncated next event from %d to %zd bytes", n,
sizeof(buffer));
if ((size_t)n < (sizeof(buffer) - 1))
n += vsnprintf(buffer + n, sizeof(buffer) - n, event->fmt, *event->vap);
else
n = sizeof(buffer) - 1;
}
buffer[n] = '\n';