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module-rt: Protect setrlimit() with mutex

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Make sure threads initializing the module doesn't get/set RLIMIT_RTTIME
simultaneously.
This commit is contained in:
Jonas Holmberg 2023-11-22 14:35:24 +01:00 • committed by Wim Taymans
parent f324f0e8e1
commit 72323dcaf3
1 changed files with 31 additions and 21 deletions
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52
src/modules/module-rt.c
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@ -230,6 +230,8 @@ struct impl {
#define RLIMIT_RTTIME 15
#endif
static pthread_mutex_t rlimit_lock = PTHREAD_MUTEX_INITIALIZER;
static pid_t _gettid(void)
{
#if defined(HAVE_GETTID)
@ -556,11 +558,12 @@ static bool check_realtime_privileges(struct impl *impl)
struct rlimit old_rlim;
struct rlimit no_rlim = { -1, -1 };
int try = 0;
bool ret = false;
if (!impl->rlimits_enabled)
return false;
return ret;
while (try++ < 2) {
while (!ret && try++ < 2) {
/* We could check `RLIMIT_RTPRIO`, but the BSDs generally don't have
* that available, and there are also other ways to use realtime
* scheduling without that rlimit being set such as `CAP_SYS_NICE` or
@ -568,11 +571,11 @@ static bool check_realtime_privileges(struct impl *impl)
* just try if setting realtime scheduling works or not. */
if ((err = pthread_getschedparam(pthread_self(), &old_policy, &old_sched_params)) != 0) {
pw_log_warn("Failed to check RLIMIT_RTPRIO: %s", strerror(err));
return false;
break;
}
if ((err = get_rt_priority_range(&min, &max)) < 0) {
pw_log_warn("Failed to get priority range: %s", strerror(err));
return false;
break;
}
if (try == 2) {
#ifdef RLIMIT_RTPRIO
@ -588,7 +591,7 @@ static bool check_realtime_privileges(struct impl *impl)
}
if (max < DEFAULT_RT_PRIO_MIN) {
pw_log_info("Priority max (%d) must be at least %d", max, DEFAULT_RT_PRIO_MIN);
return false;
break;
}
/* If the current scheduling policy has `SCHED_RESET_ON_FORK` set, then
@ -602,24 +605,29 @@ static bool check_realtime_privileges(struct impl *impl)
if ((old_policy & PW_SCHED_RESET_ON_FORK) != 0)
new_policy |= PW_SCHED_RESET_ON_FORK;
/* Disable RLIMIT_RTTIME while trying new_policy. */
if ((err = getrlimit(RLIMIT_RTTIME, &old_rlim)) < 0)
pw_log_debug("getrlimit() failed: %s", spa_strerror(err));
if ((err = setrlimit(RLIMIT_RTTIME, &no_rlim)) < 0)
pw_log_debug("setrlimit() failed: %s", spa_strerror(err));
if (pthread_setschedparam(pthread_self(), new_policy, &new_sched_params) == 0) {
/* Disable RLIMIT_RTTIME in a thread safe way and hope that the application
* doesn't also set RLIMIT_RTTIME while trying new_policy. */
pthread_mutex_lock(&rlimit_lock);
if (getrlimit(RLIMIT_RTTIME, &old_rlim) < 0)
pw_log_info("getrlimit() failed: %m");
if (setrlimit(RLIMIT_RTTIME, &no_rlim) < 0)
pw_log_info("setrlimit() failed: %m");
if (err = pthread_setschedparam(pthread_self(), new_policy, &new_sched_params) == 0) {
impl->rt_prio = new_sched_params.sched_priority;
pthread_setschedparam(pthread_self(), old_policy, &old_sched_params);
if ((err = setrlimit(RLIMIT_RTTIME, &old_rlim)) < 0)
pw_log_debug("setrlimit() failed: %s", spa_strerror(err));
return true;
}
if ((err = setrlimit(RLIMIT_RTTIME, &old_rlim)) < 0)
pw_log_debug("setrlimit() failed: %s", spa_strerror(err));
ret = true;
} else
pw_log_info("failed to set realtime policy: %s", strerror(err));
if (setrlimit(RLIMIT_RTTIME, &old_rlim) < 0)
pw_log_info("setrlimit() failed: %m");
pthread_mutex_unlock(&rlimit_lock);
}
pw_log_info("Can't set rt prio to %d: %m (try increasing rlimits)", (int)priority);
return false;
if (ret)
pw_log_debug("can set rt prio to %d", (int)priority);
else
pw_log_info("can't set rt prio to %d (try increasing rlimits)", (int)priority);
return ret;
}
static int sched_set_nice(pid_t pid, int nice_level)
@ -668,11 +676,13 @@ static int set_rlimit(struct rlimit *rlim)
{
int res = 0;
pthread_mutex_lock(&rlimit_lock);
if (setrlimit(RLIMIT_RTTIME, rlim) < 0)
res = -errno;
pthread_mutex_unlock(&rlimit_lock);
if (res < 0)
pw_log_debug("setrlimit() failed: %s", spa_strerror(res));
pw_log_info("setrlimit() failed: %s", spa_strerror(res));
else
pw_log_debug("rt.time.soft:%"PRIi64" rt.time.hard:%"PRIi64,
(int64_t)rlim->rlim_cur, (int64_t)rlim->rlim_max);