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locking: update per Dwight's comment

Browse Source 
Create three pairs of functions:
	int process_lock(void);
	void process_unlock(void);
	int container_mem_lock(struct lxc_container *c)
	void container_mem_unlock(struct lxc_container *c)
	int container_disk_lock(struct lxc_container *c);
	void container_disk_unlock(struct lxc_container *c);

and use those in lxccontainer.c

process_lock() is to protect the process state among multiple threads.
container_mem_lock() is to protect a struct container among multiple
threads.  container_disk_lock is to protect a container on disk.

Also remove the lock in lxcapi_init_pid() as Dwight suggested.

Fix a typo (s/container/contain) spotted by Dwight.

More locking fixes are needed, but let's first the the fundamentals
right.  How close does this get us?

Changelog: v2:
	fix lxclock compile

Signed-off-by: Serge Hallyn <serge.hallyn@ubuntu.com>
Acked-by: Dwight Engen <dwight.engen@oracle.com>
This commit is contained in:
Serge Hallyn 2013-05-24 16:03:22 -05:00
parent df271a59cb
commit 5cee8c5040
3 changed files with 119 additions and 117 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

129
src/lxc/lxccontainer.c
View File

@ -43,8 +43,6 @@
#include <arpa/inet.h> #include <arpa/inet.h>
#include <ifaddrs.h> #include <ifaddrs.h>
extern pthread_mutex_t thread_mutex;
lxc_log_define(lxc_container, lxc); lxc_log_define(lxc_container, lxc);
/* LOCKING /* LOCKING
@ -138,7 +136,7 @@ int lxc_container_get(struct lxc_container *c)
if (c->numthreads < 1) if (c->numthreads < 1)
return 0; return 0;
if (lxclock(c->privlock, 0)) if (container_mem_lock(c))
return 0; return 0;
if (c->numthreads < 1) { if (c->numthreads < 1) {
// bail without trying to unlock, bc the privlock is now probably // bail without trying to unlock, bc the privlock is now probably
@ -146,7 +144,7 @@ int lxc_container_get(struct lxc_container *c)
return 0; return 0;
} }
c->numthreads++; c->numthreads++;
lxcunlock(c->privlock); container_mem_unlock(c);
return 1; return 1;
} }
@ -154,14 +152,14 @@ int lxc_container_put(struct lxc_container *c)
{ {
if (!c) if (!c)
return -1; return -1;
if (lxclock(c->privlock, 0)) if (container_mem_lock(c))
return -1; return -1;
if (--c->numthreads < 1) { if (--c->numthreads < 1) {
lxcunlock(c->privlock); container_mem_unlock(c);
lxc_container_free(c); lxc_container_free(c);
return 1; return 1;
} }
lxcunlock(c->privlock); container_mem_unlock(c);
return 0; return 0;
} }
@ -181,7 +179,7 @@ static bool lxcapi_is_defined(struct lxc_container *c)
if (!c) if (!c)
return false; return false;
if (lxclock(c->privlock, 0)) if (container_mem_lock(c))
return false; return false;
if (!c->configfile) if (!c->configfile)
goto out; goto out;
@ -191,7 +189,7 @@ static bool lxcapi_is_defined(struct lxc_container *c)
ret = true; ret = true;
out: out:
lxcunlock(c->privlock); container_mem_unlock(c);
return ret; return ret;
} }
@ -202,15 +200,11 @@ static const char *lxcapi_state(struct lxc_container *c)
if (!c) if (!c)
return NULL; return NULL;
if (lxclock(c->privlock, 0)) if (container_disk_lock(c))
return NULL; return NULL;
if (lxclock(c->slock, 0))
goto bad;
s = lxc_getstate(c->name, c->config_path); s = lxc_getstate(c->name, c->config_path);
ret = lxc_state2str(s); ret = lxc_state2str(s);
lxcunlock(c->slock); container_disk_unlock(c);
bad:
lxcunlock(c->privlock);
return ret; return ret;
} }
@ -240,15 +234,10 @@ static bool lxcapi_freeze(struct lxc_container *c)
if (!c) if (!c)
return false; return false;
if (lxclock(c->privlock, 0)) if (container_disk_lock(c))
return false; return false;
if (lxclock(c->slock, 0)) {
lxcunlock(c->privlock);
return false;
}
ret = lxc_freeze(c->name, c->config_path); ret = lxc_freeze(c->name, c->config_path);
lxcunlock(c->slock); container_disk_unlock(c);
lxcunlock(c->privlock);
if (ret) if (ret)
return false; return false;
return true; return true;
@ -260,15 +249,10 @@ static bool lxcapi_unfreeze(struct lxc_container *c)
if (!c) if (!c)
return false; return false;
if (lxclock(c->privlock, 0)) if (container_disk_lock(c))
return false; return false;
if (lxclock(c->slock, 0)) {
lxcunlock(c->privlock);
return false;
}
ret = lxc_unfreeze(c->name, c->config_path); ret = lxc_unfreeze(c->name, c->config_path);
lxcunlock(c->slock); container_disk_unlock(c);
lxcunlock(c->privlock);
if (ret) if (ret)
return false; return false;
return true; return true;
@ -276,20 +260,10 @@ static bool lxcapi_unfreeze(struct lxc_container *c)
static pid_t lxcapi_init_pid(struct lxc_container *c) static pid_t lxcapi_init_pid(struct lxc_container *c)
{ {
pid_t ret;
if (!c) if (!c)
return -1; return -1;
if (lxclock(c->privlock, 0)) return lxc_cmd_get_init_pid(c->name, c->config_path);
return -1;
if (lxclock(c->slock, 0)) {
lxcunlock(c->privlock);
return -1;
}
ret = lxc_cmd_get_init_pid(c->name, c->config_path);
lxcunlock(c->slock);
lxcunlock(c->privlock);
return ret;
} }
static bool load_config_locked(struct lxc_container *c, const char *fname) static bool load_config_locked(struct lxc_container *c, const char *fname)
@ -313,15 +287,10 @@ static bool lxcapi_load_config(struct lxc_container *c, const char *alt_file)
fname = alt_file; fname = alt_file;
if (!fname) if (!fname)
return false; return false;
if (lxclock(c->privlock, 0)) if (container_disk_lock(c))
return false; return false;
if (lxclock(c->slock, 0)) {
lxcunlock(c->privlock);
return false;
}
ret = load_config_locked(c, fname); ret = load_config_locked(c, fname);
lxcunlock(c->slock); container_disk_unlock(c);
lxcunlock(c->privlock);
return ret; return ret;
} }
@ -384,11 +353,11 @@ static bool lxcapi_start(struct lxc_container *c, int useinit, char * const argv
if (useinit && !argv) if (useinit && !argv)
return false; return false;
if (lxclock(c->privlock, 0)) if (container_mem_lock(c))
return false; return false;
conf = c->lxc_conf; conf = c->lxc_conf;
daemonize = c->daemonize; daemonize = c->daemonize;
lxcunlock(c->privlock); container_mem_unlock(c);
if (useinit) { if (useinit) {
ret = lxc_execute(c->name, argv, 1, conf, c->config_path); ret = lxc_execute(c->name, argv, 1, conf, c->config_path);
@ -409,23 +378,20 @@ static bool lxcapi_start(struct lxc_container *c, int useinit, char * const argv
return false; return false;
lxc_monitord_spawn(c->config_path); lxc_monitord_spawn(c->config_path);
ret = pthread_mutex_lock(&thread_mutex); if (process_lock())
if (ret != 0) {
ERROR("pthread_mutex_lock returned:%d %s", ret, strerror(ret));
return false; return false;
}
pid_t pid = fork(); pid_t pid = fork();
if (pid < 0) { if (pid < 0) {
lxc_container_put(c); lxc_container_put(c);
pthread_mutex_unlock(&thread_mutex); process_unlock();
return false; return false;
} }
if (pid != 0) { if (pid != 0) {
ret = wait_on_daemonized_start(c); ret = wait_on_daemonized_start(c);
pthread_mutex_unlock(&thread_mutex); process_unlock();
return ret; return ret;
} }
pthread_mutex_unlock(&thread_mutex); process_unlock();
/* second fork to be reparented by init */ /* second fork to be reparented by init */
pid = fork(); pid = fork();
if (pid < 0) { if (pid < 0) {
@ -613,13 +579,8 @@ static bool lxcapi_create(struct lxc_container *c, const char *t, char *const ar
/* we're going to fork. but since we'll wait for our child, we /* we're going to fork. but since we'll wait for our child, we
* don't need to lxc_container_get */ * don't need to lxc_container_get */
if (lxclock(c->privlock, 0)) if (container_disk_lock(c))
goto out; goto out;
if (lxclock(c->slock, 0)) {
ERROR("failed to grab global container lock for %s\n", c->name);
lxcunlock(c->privlock);
goto out_unlock1;
}
pid = fork(); pid = fork();
if (pid < 0) { if (pid < 0) {
@ -698,9 +659,7 @@ static bool lxcapi_create(struct lxc_container *c, const char *t, char *const ar
bret = load_config_locked(c, c->configfile); bret = load_config_locked(c, c->configfile);
out_unlock: out_unlock:
lxcunlock(c->slock); container_disk_unlock(c);
out_unlock1:
lxcunlock(c->privlock);
out: out:
if (tpath) if (tpath)
free(tpath); free(tpath);
@ -778,11 +737,10 @@ static bool lxcapi_clear_config_item(struct lxc_container *c, const char *key)
if (!c || !c->lxc_conf) if (!c || !c->lxc_conf)
return false; return false;
if (lxclock(c->privlock, 0)) { if (container_mem_lock(c))
return false; return false;
}
ret = lxc_clear_config_item(c->lxc_conf, key); ret = lxc_clear_config_item(c->lxc_conf, key);
lxcunlock(c->privlock); container_mem_unlock(c);
return ret == 0; return ret == 0;
} }
@ -904,11 +862,10 @@ static int lxcapi_get_config_item(struct lxc_container *c, const char *key, char
if (!c || !c->lxc_conf) if (!c || !c->lxc_conf)
return -1; return -1;
if (lxclock(c->privlock, 0)) { if (container_mem_lock(c))
return -1; return -1;
}
ret = lxc_get_config_item(c->lxc_conf, key, retv, inlen); ret = lxc_get_config_item(c->lxc_conf, key, retv, inlen);
lxcunlock(c->privlock); container_mem_unlock(c);
return ret; return ret;
} }
@ -923,12 +880,12 @@ static int lxcapi_get_keys(struct lxc_container *c, const char *key, char *retv,
*/ */
if (!c || !c->lxc_conf) if (!c || !c->lxc_conf)
return -1; return -1;
if (lxclock(c->privlock, 0)) if (container_mem_lock(c))
return -1; return -1;
int ret = -1; int ret = -1;
if (strncmp(key, "lxc.network.", 12) == 0) if (strncmp(key, "lxc.network.", 12) == 0)
ret = lxc_list_nicconfigs(c->lxc_conf, key, retv, inlen); ret = lxc_list_nicconfigs(c->lxc_conf, key, retv, inlen);
lxcunlock(c->privlock); container_mem_unlock(c);
return ret; return ret;
} }
@ -953,13 +910,13 @@ static bool lxcapi_save_config(struct lxc_container *c, const char *alt_file)
FILE *fout = fopen(alt_file, "w"); FILE *fout = fopen(alt_file, "w");
if (!fout) if (!fout)
return false; return false;
if (lxclock(c->privlock, 0)) { if (container_mem_lock(c)) {
fclose(fout); fclose(fout);
return false; return false;
} }
write_config(fout, c->lxc_conf); write_config(fout, c->lxc_conf);
fclose(fout); fclose(fout);
lxcunlock(c->privlock); container_mem_unlock(c);
return true; return true;
} }
@ -1000,7 +957,7 @@ static bool lxcapi_set_config_item(struct lxc_container *c, const char *key, con
if (!c) if (!c)
return false; return false;
if (lxclock(c->privlock, 0)) if (container_mem_lock(c))
return false; return false;
if (!c->lxc_conf) if (!c->lxc_conf)
@ -1015,7 +972,7 @@ static bool lxcapi_set_config_item(struct lxc_container *c, const char *key, con
b = true; b = true;
err: err:
lxcunlock(c->privlock); container_mem_unlock(c);
return b; return b;
} }
@ -1076,7 +1033,7 @@ static bool lxcapi_set_config_path(struct lxc_container *c, const char *path)
if (!c) if (!c)
return b; return b;
if (lxclock(c->privlock, 0)) if (container_mem_lock(c))
return b; return b;
p = strdup(path); p = strdup(path);
@ -1102,7 +1059,7 @@ static bool lxcapi_set_config_path(struct lxc_container *c, const char *path)
err: err:
if (oldpath) if (oldpath)
free(oldpath); free(oldpath);
lxcunlock(c->privlock); container_mem_unlock(c);
return b; return b;
} }
@ -1115,7 +1072,7 @@ static bool lxcapi_set_cgroup_item(struct lxc_container *c, const char *subsys,
if (!c) if (!c)
return false; return false;
if (lxclock(c->privlock, 0)) if (container_mem_lock(c))
return false; return false;
if (is_stopped_nolock(c)) if (is_stopped_nolock(c))
@ -1125,7 +1082,7 @@ static bool lxcapi_set_cgroup_item(struct lxc_container *c, const char *subsys,
if (!ret) if (!ret)
b = true; b = true;
err: err:
lxcunlock(c->privlock); container_mem_unlock(c);
return b; return b;
} }
@ -1136,7 +1093,7 @@ static int lxcapi_get_cgroup_item(struct lxc_container *c, const char *subsys, c
if (!c || !c->lxc_conf) if (!c || !c->lxc_conf)
return -1; return -1;
if (lxclock(c->privlock, 0)) if (container_mem_lock(c))
return -1; return -1;
if (is_stopped_nolock(c)) if (is_stopped_nolock(c))
@ -1145,7 +1102,7 @@ static int lxcapi_get_cgroup_item(struct lxc_container *c, const char *subsys, c
ret = lxc_cgroup_get(c->name, subsys, retv, inlen, c->config_path); ret = lxc_cgroup_get(c->name, subsys, retv, inlen, c->config_path);
out: out:
lxcunlock(c->privlock); container_mem_unlock(c);
return ret; return ret;
} }
@ -1600,7 +1557,7 @@ struct lxc_container *lxcapi_clone(struct lxc_container *c, const char *newname,
if (!c || !c->is_defined(c)) if (!c || !c->is_defined(c))
return NULL; return NULL;
if (lxclock(c->privlock, 0)) if (container_mem_lock(c))
return NULL; return NULL;
if (c->is_running(c)) { if (c->is_running(c)) {
@ -1682,11 +1639,11 @@ struct lxc_container *lxcapi_clone(struct lxc_container *c, const char *newname,
goto out; goto out;
// TODO: update c's lxc.snapshot = count // TODO: update c's lxc.snapshot = count
lxcunlock(c->privlock); container_mem_unlock(c);
return c2; return c2;
out: out:
lxcunlock(c->privlock); container_mem_unlock(c);
if (c2) { if (c2) {
c2->destroy(c2); c2->destroy(c2);
lxc_container_put(c2); lxc_container_put(c2);

94
src/lxc/lxclock.c
View File

@ -25,6 +25,7 @@
#include <unistd.h> #include <unistd.h>
#include <lxc/utils.h> #include <lxc/utils.h>
#include <lxc/log.h> #include <lxc/log.h>
#include <lxc/lxccontainer.h>
#define OFLAG (O_CREAT | O_RDWR) #define OFLAG (O_CREAT | O_RDWR)
#define SEMMODE 0660 #define SEMMODE 0660
@ -48,7 +49,10 @@ static char *lxclock_name(const char *p, const char *n)
free(dest); free(dest);
return NULL; return NULL;
} }
if (mkdir_p(dest, 0755) < 0) { process_lock();
ret = mkdir_p(dest, 0755);
process_unlock();
if (ret < 0) {
free(dest); free(dest);
return NULL; return NULL;
} }
@ -80,11 +84,6 @@ static sem_t *lxc_new_unnamed_sem(void)
struct lxc_lock *lxc_newlock(const char *lxcpath, const char *name) struct lxc_lock *lxc_newlock(const char *lxcpath, const char *name)
{ {
struct lxc_lock *l; struct lxc_lock *l;
int ret = pthread_mutex_lock(&thread_mutex);
if (ret != 0) {
ERROR("pthread_mutex_lock returned:%d %s", ret, strerror(ret));
return NULL;
}
l = malloc(sizeof(*l)); l = malloc(sizeof(*l));
if (!l) if (!l)
@ -106,18 +105,12 @@ struct lxc_lock *lxc_newlock(const char *lxcpath, const char *name)
l->u.f.fd = -1; l->u.f.fd = -1;
out: out:
pthread_mutex_unlock(&thread_mutex);
return l; return l;
} }
int lxclock(struct lxc_lock *l, int timeout) int lxclock(struct lxc_lock *l, int timeout)
{ {
int saved_errno = errno; int ret = -1, saved_errno = errno;
int ret = pthread_mutex_lock(&thread_mutex);
if (ret != 0) {
ERROR("pthread_mutex_lock returned:%d %s", ret, strerror(ret));
return ret;
}
switch(l->type) { switch(l->type) {
case LXC_LOCK_ANON_SEM: case LXC_LOCK_ANON_SEM:
@ -149,35 +142,31 @@ int lxclock(struct lxc_lock *l, int timeout)
ret = -2; ret = -2;
goto out; goto out;
} }
process_lock();
if (l->u.f.fd == -1) { if (l->u.f.fd == -1) {
l->u.f.fd = open(l->u.f.fname, O_RDWR|O_CREAT, l->u.f.fd = open(l->u.f.fname, O_RDWR|O_CREAT,
S_IWUSR | S_IRUSR); S_IWUSR | S_IRUSR);
if (l->u.f.fd == -1) { if (l->u.f.fd == -1) {
process_unlock();
ERROR("Error opening %s", l->u.f.fname); ERROR("Error opening %s", l->u.f.fname);
goto out; goto out;
} }
} }
ret = flock(l->u.f.fd, LOCK_EX); ret = flock(l->u.f.fd, LOCK_EX);
process_unlock();
if (ret == -1) if (ret == -1)
saved_errno = errno; saved_errno = errno;
break; break;
} }
out: out:
pthread_mutex_unlock(&thread_mutex);
errno = saved_errno; errno = saved_errno;
return ret; return ret;
} }
int lxcunlock(struct lxc_lock *l) int lxcunlock(struct lxc_lock *l)
{ {
int saved_errno = errno; int ret = 0, saved_errno = errno;
int ret = pthread_mutex_lock(&thread_mutex);
if (ret != 0) {
ERROR("pthread_mutex_lock returned:%d %s", ret, strerror(ret));
return ret;
}
switch(l->type) { switch(l->type) {
case LXC_LOCK_ANON_SEM: case LXC_LOCK_ANON_SEM:
@ -188,6 +177,7 @@ int lxcunlock(struct lxc_lock *l)
saved_errno = errno; saved_errno = errno;
break; break;
case LXC_LOCK_FLOCK: case LXC_LOCK_FLOCK:
process_lock();
if (l->u.f.fd != -1) { if (l->u.f.fd != -1) {
if ((ret = flock(l->u.f.fd, LOCK_UN)) < 0) if ((ret = flock(l->u.f.fd, LOCK_UN)) < 0)
saved_errno = errno; saved_errno = errno;
@ -195,40 +185,84 @@ int lxcunlock(struct lxc_lock *l)
l->u.f.fd = -1; l->u.f.fd = -1;
} else } else
ret = -2; ret = -2;
process_unlock();
break; break;
} }
pthread_mutex_unlock(&thread_mutex);
errno = saved_errno; errno = saved_errno;
return ret; return ret;
} }
/*
* lxc_putlock() is only called when a container_new() fails,
* or during container_put(), which is already guaranteed to
* only be done by one task.
* So the only exclusion we need to provide here is for regular
* thread safety (i.e. file descriptor table changes).
*/
void lxc_putlock(struct lxc_lock *l) void lxc_putlock(struct lxc_lock *l)
{ {
int ret = pthread_mutex_lock(&thread_mutex);
if (ret != 0) {
ERROR("pthread_mutex_lock returned:%d %s", ret, strerror(ret));
return;
}
if (!l) if (!l)
goto out; return;
switch(l->type) { switch(l->type) {
case LXC_LOCK_ANON_SEM: case LXC_LOCK_ANON_SEM:
if (l->u.sem) if (l->u.sem)
sem_close(l->u.sem); sem_close(l->u.sem);
break; break;
case LXC_LOCK_FLOCK: case LXC_LOCK_FLOCK:
process_lock();
if (l->u.f.fd != -1) { if (l->u.f.fd != -1) {
close(l->u.f.fd); close(l->u.f.fd);
l->u.f.fd = -1; l->u.f.fd = -1;
} }
process_unlock();
if (l->u.f.fname) { if (l->u.f.fname) {
free(l->u.f.fname); free(l->u.f.fname);
l->u.f.fname = NULL; l->u.f.fname = NULL;
} }
break; break;
} }
out: }
int process_lock(void)
{
int ret;
ret = pthread_mutex_lock(&thread_mutex);
if (ret != 0)
ERROR("pthread_mutex_lock returned:%d %s", ret, strerror(ret));
return ret;
}
void process_unlock(void)
{
pthread_mutex_unlock(&thread_mutex); pthread_mutex_unlock(&thread_mutex);
} }
int container_mem_lock(struct lxc_container *c)
{
return lxclock(c->privlock, 0);
}
void container_mem_unlock(struct lxc_container *c)
{
lxcunlock(c->privlock);
}
int container_disk_lock(struct lxc_container *c)
{
int ret;
if ((ret = lxclock(c->privlock, 0)))
return ret;
if ((ret = lxclock(c->slock, 0))) {
lxcunlock(c->privlock);
return ret;
}
return 0;
}
void container_disk_unlock(struct lxc_container *c)
{
lxcunlock(c->slock);
lxcunlock(c->privlock);
}

13
src/lxc/lxclock.h
View File

@ -1,3 +1,5 @@
#ifndef __LXCLOCK_H
#define __LXCLOCK_H
/* liblxcapi /* liblxcapi
* *
* Copyright © 2012 Serge Hallyn <serge.hallyn@ubuntu.com>. * Copyright © 2012 Serge Hallyn <serge.hallyn@ubuntu.com>.
@ -53,7 +55,7 @@ struct lxc_lock {
* We use that to protect the containers as represented on disk. * We use that to protect the containers as represented on disk.
* lxc_newlock() for the named lock only allocates the pathname in * lxc_newlock() for the named lock only allocates the pathname in
* memory so we can quickly open+lock it at lxclock. * memory so we can quickly open+lock it at lxclock.
* l->u.f.fname will container the malloc'ed name (which must be * l->u.f.fname will contain the malloc'ed name (which must be
* freed when the container is freed), and u.f.fd = -1. * freed when the container is freed), and u.f.fd = -1.
* *
* return lxclock on success, NULL on failure. * return lxclock on success, NULL on failure.
@ -81,3 +83,12 @@ extern int lxclock(struct lxc_lock *lock, int timeout);
extern int lxcunlock(struct lxc_lock *lock); extern int lxcunlock(struct lxc_lock *lock);
extern void lxc_putlock(struct lxc_lock *l); extern void lxc_putlock(struct lxc_lock *l);
extern int process_lock(void);
extern void process_unlock(void);
struct lxc_container;
extern int container_mem_lock(struct lxc_container *c);
extern void container_mem_unlock(struct lxc_container *c);
extern int container_disk_lock(struct lxc_container *c);
extern void container_disk_unlock(struct lxc_container *c);
#endif