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authorKrutika Dhananjay <kdhananj@redhat.com>2014-04-24 16:37:05 +0530
committerAnand Avati <avati@redhat.com>2014-04-26 00:52:25 -0700
commit6a188c6b2c95d16c1bb6391c9fcb8ef808c2141b (patch)
tree4af0e88cae2d1a7807b647c59e930bc4678aa9ed
parent0af287791f0d50b5d2975cb2e2c902c797b05860 (diff)
features/locks: Remove stale entrylk objects from 'blocked_locks' list
* In the event of a DISCONNECT from a client, as part of cleanup, entrylk objects are not removed from the blocked_locks list before being unref'd and freed, causing the brick process to crash at some point when the (now) stale object is accessed again in the list. * Also during cleanup, it is pointless to try and grant lock to a previously blocked entrylk (say L1) as part of releasing another conflicting lock (L2), (which is a side-effect of L1 not being deleted from blocked_locks list before grant_blocked_entry_locks() in cleanup) if L1 is also associated with the DISCONNECTing client. This patch fixes the problem. Change-Id: I3d684c6bafc7e6db89ba68f0a2ed1dcb333791c6 BUG: 1089470 Signed-off-by: Krutika Dhananjay <kdhananj@redhat.com> Reviewed-on: http://review.gluster.org/7560 Reviewed-by: Pranith Kumar Karampuri <pkarampu@redhat.com> Tested-by: Gluster Build System <jenkins@build.gluster.com> Reviewed-by: Anand Avati <avati@redhat.com>
-rw-r--r--xlators/features/locks/src/entrylk.c50
-rw-r--r--xlators/features/locks/src/inodelk.c2
2 files changed, 48 insertions, 4 deletions
diff --git a/xlators/features/locks/src/entrylk.c b/xlators/features/locks/src/entrylk.c
index 4f5d8ac..8496d9d 100644
--- a/xlators/features/locks/src/entrylk.c
+++ b/xlators/features/locks/src/entrylk.c
@@ -715,15 +715,16 @@ pl_entrylk_client_cleanup (xlator_t *this, pl_ctx_t *ctx)
pl_inode_t *pinode = NULL;
struct list_head released;
+ struct list_head unwind;
INIT_LIST_HEAD (&released);
+ INIT_LIST_HEAD (&unwind);
pthread_mutex_lock (&ctx->lock);
{
list_for_each_entry_safe (l, tmp, &ctx->entrylk_lockers,
client_list) {
list_del_init (&l->client_list);
- list_add_tail (&l->client_list, &released);
pl_entrylk_log_cleanup (l);
@@ -731,19 +732,62 @@ pl_entrylk_client_cleanup (xlator_t *this, pl_ctx_t *ctx)
pthread_mutex_lock (&pinode->mutex);
{
- list_del_init (&l->domain_list);
+ /* If the entrylk object is part of granted list but not
+ * blocked list, then perform the following actions:
+ * i. delete the object from granted list;
+ * ii. grant other locks (from other clients) that may
+ * have been blocked on this entrylk; and
+ * iii. unref the object.
+ *
+ * If the entrylk object (L1) is part of both granted
+ * and blocked lists, then this means that a parallel
+ * unlock on another entrylk (L2 say) may have 'granted'
+ * L1 and added it to 'granted' list in
+ * __grant_blocked_entry_locks() (although using the
+ * 'blocked_locks' member). In that case, the cleanup
+ * codepath must try and grant other overlapping
+ * blocked entrylks from other clients, now that L1 is
+ * out of their way and then unref L1 in the end, and
+ * leave it to the other thread (the one executing
+ * unlock codepath) to unwind L1's frame, delete it from
+ * blocked_locks list, and perform the last unref on L1.
+ *
+ * If the entrylk object (L1) is part of blocked list
+ * only, the cleanup code path must:
+ * i. delete it from the blocked_locks list inside
+ * this critical section,
+ * ii. unwind its frame with EAGAIN,
+ * iii. try and grant blocked entry locks from other
+ * clients that were otherwise grantable, but were
+ * blocked to avoid leaving L1 to starve forever.
+ * iv. unref the object.
+ */
+ if (!list_empty (&l->domain_list)) {
+ list_del_init (&l->domain_list);
+ list_add_tail (&l->client_list,
+ &released);
+ } else {
+ list_del_init (&l->blocked_locks);
+ list_add_tail (&l->client_list,
+ &unwind);
+ }
}
pthread_mutex_unlock (&pinode->mutex);
}
}
pthread_mutex_unlock (&ctx->lock);
- list_for_each_entry_safe (l, tmp, &released, client_list) {
+ list_for_each_entry_safe (l, tmp, &unwind, client_list) {
list_del_init (&l->client_list);
if (l->frame)
STACK_UNWIND_STRICT (entrylk, l->frame, -1, EAGAIN,
NULL);
+ list_add_tail (&l->client_list, &released);
+ }
+
+ list_for_each_entry_safe (l, tmp, &released, client_list) {
+ list_del_init (&l->client_list);
pinode = l->pinode;
diff --git a/xlators/features/locks/src/inodelk.c b/xlators/features/locks/src/inodelk.c
index d105e14..c76cb7f 100644
--- a/xlators/features/locks/src/inodelk.c
+++ b/xlators/features/locks/src/inodelk.c
@@ -26,7 +26,7 @@
inline void
__delete_inode_lock (pl_inode_lock_t *lock)
{
- list_del (&lock->list);
+ list_del_init (&lock->list);
}
static inline void