diff mbox

[PATCHv2,7/8] linux-generic: schedule: fix race condition in ordered locks

Message ID 1441293400-28777-8-git-send-email-bill.fischofer@linaro.org
State Accepted
Commit 5cdd039a6bcecae79d1fad0f2b4d52ad43c8e6d5
Headers show

Commit Message

Bill Fischofer Sept. 3, 2015, 3:16 p.m. UTC 
Correct race condition that arises due to attempt to permit ordered locks
to be reusable. For now, ordered locks can only be used once per scheduled
event.

Signed-off-by: Bill Fischofer <bill.fischofer@linaro.org>
---
 platform/linux-generic/include/odp_queue_internal.h | 6 +++++-
 platform/linux-generic/odp_queue.c                  | 8 +-------
 2 files changed, 6 insertions(+), 8 deletions(-)
diff mbox

Patch

diff --git a/platform/linux-generic/include/odp_queue_internal.h b/platform/linux-generic/include/odp_queue_internal.h
index 48576bc..0f30965 100644
--- a/platform/linux-generic/include/odp_queue_internal.h
+++ b/platform/linux-generic/include/odp_queue_internal.h
@@ -193,8 +193,12 @@  static inline void reorder_enq(queue_entry_t *queue,
 
 static inline void order_release(queue_entry_t *origin_qe, int count)
 {
+	uint64_t sync = odp_atomic_load_u64(&origin_qe->s.sync_out);
+
 	origin_qe->s.order_out += count;
-	odp_atomic_fetch_add_u64(&origin_qe->s.sync_out, count);
+	if (sync < origin_qe->s.order_out)
+		odp_atomic_fetch_add_u64(&origin_qe->s.sync_out,
+					 origin_qe->s.order_out - sync);
 }
 
 static inline int reorder_deq(queue_entry_t *queue,
diff --git a/platform/linux-generic/odp_queue.c b/platform/linux-generic/odp_queue.c
index 15abd93..ac933da 100644
--- a/platform/linux-generic/odp_queue.c
+++ b/platform/linux-generic/odp_queue.c
@@ -999,12 +999,6 @@  void odp_schedule_order_unlock(odp_schedule_order_lock_t *lock ODP_UNUSED)
 	if (!origin_qe)
 		return;
 
-	/* Get a new sync order for reusability, and release the lock. Note
-	 * that this must be done in this sequence to prevent race conditions
-	 * where the next waiter could lock and unlock before we're able to
-	 * get a new sync order since that would cause order inversion on
-	 * subsequent locks we may perform in this ordered context.
-	 */
-	*sync = odp_atomic_fetch_inc_u64(&origin_qe->s.sync_in);
+	/* Release the ordered lock */
 	odp_atomic_fetch_inc_u64(&origin_qe->s.sync_out);
 }