Revert "osq_lock: fix osq_lock queue corruption"

This reverts commit ba6bd90a30896933174c26e2d96d4df9acfcb75c.

Perparing for taking more optimized patch suggested to upstream
for using smp_wmb() instead of smp_mb().

Change-Id: Idc4fbd884055d9a8f65f102862dd276abe54699d
Signed-off-by: Prateek Sood <prsood@codeaurora.org>

1 files changed, 0 insertions, 26 deletions

diff --git a/kernel/locking/osq_lock.c b/kernel/locking/osq_lock.c
index 1e6a51cc25c4..99b8d991126f 100644
--- a/kernel/locking/osq_lock.c
+++ b/kernel/locking/osq_lock.c
@@ -106,32 +106,6 @@ bool osq_lock(struct optimistic_spin_queue *lock)
 
 	prev = decode_cpu(old);
 	node->prev = prev;
-
-	/*
-	 * We need to avoid reordering of link updation sequence of osq.
-	 * A case in which the status of optimistic spin queue is
-	 * CPU6->CPU2 in which CPU6 has acquired the lock. At this point
-	 * if CPU0 comes in to acquire osq_lock, it will update the tail
-	 * count. After tail count update if CPU2 starts to unqueue itself
-	 * from optimistic spin queue, it will find updated tail count with
-	 * CPU0 and update CPU2 node->next to NULL in osq_wait_next(). If
-	 * reordering of following stores happen then prev->next where prev
-	 * being CPU2 would be updated to point to CPU0 node:
-	 *      node->prev = prev;
-	 *      WRITE_ONCE(prev->next, node);
-	 *
-	 * At this point if next instruction
-	 *      WRITE_ONCE(next->prev, prev);
-	 * in CPU2 path is committed before the update of CPU0 node->prev =
-	 * prev then CPU0 node->prev will point to CPU6 node. At this point
-	 * if CPU0 path's node->prev = prev is committed resulting in change
-	 * of CPU0 prev back to CPU2 node. CPU2 node->next is NULL, so if
-	 * CPU0 gets into unqueue path of osq_lock it will keep spinning
-	 * in infinite loop as condition prev->next == node will never be
-	 * true.
-	 */
-	smp_mb();
-
 	WRITE_ONCE(prev->next, node);
 
 	/*