From: Martin Wilck <mwilck@xxxxxxxx>
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 <mwilck@xxxxxxxx>
---
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
--
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