From: Martin Wilck <[email protected]> This fixes several issues with the log_thread. First, the running flag logq_running should be set by the thread itself, not by log_thread_start()/_stop(). Second, the thread was both cancelled and terminated via a flag (again, logq_running). It's sufficient to just cancel and join it. Third, the locking wasn't cancel-safe in some places. Forth, log_thread_start() didn't wait for startup properly. Fifth, using (pthread_t)0 is wrong (pthread_t is opaque; there's no guarantee that 0 is not a valid pthread_t value). Sixth, pthread_cancel() was called under logq_lock, which doesn't make sense to me.
Signed-off-by: Martin Wilck <[email protected]> --- libmultipath/log_pthread.c | 62 +++++++++++++++++++++++++++----------- 1 file changed, 45 insertions(+), 17 deletions(-) diff --git a/libmultipath/log_pthread.c b/libmultipath/log_pthread.c index 0c327ff..3a2566a 100644 --- a/libmultipath/log_pthread.c +++ b/libmultipath/log_pthread.c @@ -13,6 +13,7 @@ #include "log_pthread.h" #include "log.h" #include "lock.h" +#include "util.h" static pthread_t log_thr; @@ -56,35 +57,52 @@ static void flush_logqueue (void) } while (empty == 0); } +static void cleanup_log_thread(__attribute((unused)) void *arg) +{ + logdbg(stderr, "log thread exiting"); + pthread_mutex_lock(&logev_lock); + logq_running = 0; + pthread_mutex_unlock(&logev_lock); +} + static void * log_thread (__attribute__((unused)) void * et) { int running; pthread_mutex_lock(&logev_lock); - logq_running = 1; + running = logq_running; + if (!running) + logq_running = 1; + pthread_cond_signal(&logev_cond); pthread_mutex_unlock(&logev_lock); + if (running) + /* already started */ + return NULL; + pthread_cleanup_push(cleanup_log_thread, NULL); mlockall(MCL_CURRENT | MCL_FUTURE); logdbg(stderr,"enter log_thread\n"); while (1) { pthread_mutex_lock(&logev_lock); - if (logq_running && !log_messages_pending) + pthread_cleanup_push(cleanup_mutex, &logev_lock); + while (!log_messages_pending) + /* this is a cancellation point */ pthread_cond_wait(&logev_cond, &logev_lock); log_messages_pending = 0; - running = logq_running; - pthread_mutex_unlock(&logev_lock); - if (!running) - break; + pthread_cleanup_pop(1); + flush_logqueue(); } + pthread_cleanup_pop(1); return NULL; } void log_thread_start (pthread_attr_t *attr) { - logdbg(stderr,"enter log_thread_start\n"); + int running = 0; + logdbg(stderr,"enter log_thread_start\n"); pthread_mutex_init(&logq_lock, NULL); pthread_mutex_init(&logev_lock, NULL); pthread_cond_init(&logev_cond, NULL); @@ -93,7 +111,15 @@ void log_thread_start (pthread_attr_t *attr) fprintf(stderr,"can't initialize log buffer\n"); exit(1); } - if (pthread_create(&log_thr, attr, log_thread, NULL)) { + + pthread_mutex_lock(&logev_lock); + pthread_cleanup_push(cleanup_mutex, &logev_lock); + if (!pthread_create(&log_thr, attr, log_thread, NULL)) + while (!(running = logq_running)) + pthread_cond_wait(&logev_cond, &logev_lock); + pthread_cleanup_pop(1); + + if (!running) { fprintf(stderr,"can't start log thread\n"); exit(1); } @@ -112,23 +138,25 @@ void log_thread_reset (void) void log_thread_stop (void) { + int running; + if (!la) return; logdbg(stderr,"enter log_thread_stop\n"); pthread_mutex_lock(&logev_lock); - logq_running = 0; - pthread_cond_signal(&logev_cond); - pthread_mutex_unlock(&logev_lock); - - pthread_mutex_lock(&logq_lock); - pthread_cancel(log_thr); - pthread_mutex_unlock(&logq_lock); - pthread_join(log_thr, NULL); - log_thr = (pthread_t)0; + pthread_cleanup_push(cleanup_mutex, &logev_lock); + running = logq_running; + if (running) { + pthread_cancel(log_thr); + pthread_cond_signal(&logev_cond); + } + pthread_cleanup_pop(1); flush_logqueue(); + if (running) + pthread_join(log_thr, NULL); pthread_mutex_destroy(&logq_lock); pthread_mutex_destroy(&logev_lock); -- 2.29.0 -- dm-devel mailing list [email protected] https://www.redhat.com/mailman/listinfo/dm-devel
