Use pthread_join() to wait until worker threads have finished
instead of using a counter to keep track of how many threads are
trying to grab a mutex. Remove mutex_lock.depth since this member
variable is no longer needed.
This patch fixes two race conditions:
* Incrementing "depth" in lock() without holding a mutex.
* Destroying a mutex from the main thread without waiting for the
worker threads to finish using that mutex.
Signed-off-by: Bart Van Assche <bart.vanassche@xxxxxxxxxxx>
---
libmultipath/lock.h | 15 +--------------
multipathd/main.c | 13 ++++++-------
2 files changed, 7 insertions(+), 21 deletions(-)
diff --git a/libmultipath/lock.h b/libmultipath/lock.h
index 9808480..a170efe 100644
--- a/libmultipath/lock.h
+++ b/libmultipath/lock.h
@@ -3,35 +3,22 @@
#include <pthread.h>
-/*
- * Wrapper for the mutex. Includes a ref-count to keep
- * track of how many there are out-standing threads blocking
- * on a mutex. */
struct mutex_lock {
pthread_mutex_t mutex;
- int depth;
};
static inline void lock(struct mutex_lock *a)
{
- a->depth++;
pthread_mutex_lock(&a->mutex);
}
static inline int timedlock(struct mutex_lock *a, struct timespec *tmo)
{
- int r;
-
- a->depth++;
- r = pthread_mutex_timedlock(&a->mutex, tmo);
- if (r)
- a->depth--;
- return r;
+ return pthread_mutex_timedlock(&a->mutex, tmo);
}
static inline void unlock(struct mutex_lock *a)
{
- a->depth--;
pthread_mutex_unlock(&a->mutex);
}
diff --git a/multipathd/main.c b/multipathd/main.c
index fff482c..c288195 100644
--- a/multipathd/main.c
+++ b/multipathd/main.c
@@ -2046,7 +2046,6 @@ init_vecs (void)
return NULL;
pthread_mutex_init(&vecs->lock.mutex, NULL);
- vecs->lock.depth = 0;
return vecs;
}
@@ -2394,16 +2393,16 @@ child (void * param)
pthread_cancel(uxlsnr_thr);
pthread_cancel(uevq_thr);
+ pthread_join(check_thr, NULL);
+ pthread_join(uevent_thr, NULL);
+ pthread_join(uxlsnr_thr, NULL);
+ pthread_join(uevq_thr, NULL);
+
lock(&vecs->lock);
free_pathvec(vecs->pathvec, FREE_PATHS);
vecs->pathvec = NULL;
unlock(&vecs->lock);
- /* Now all the waitevent threads will start rushing in. */
- while (vecs->lock.depth > 0) {
- sleep (1); /* This is weak. */
- condlog(3, "Have %d wait event checkers threads to de-alloc,"
- " waiting...", vecs->lock.depth);
- }
+
pthread_mutex_destroy(&vecs->lock.mutex);
FREE(vecs);
vecs = NULL;
--
2.9.2
--
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