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Commit 417dcdf99ec9f8d8d6917189130bdc17cb67c678

Authored by Jan Blunck
Committed by Linus Torvalds
1 parent a7d932af06
Exists in master and in 7 other branches imx_3.0.35_4.1.0, imx_3.10.17_1.0.1_ga, imx_3.10.53_1.1.0_ga, imx_3.14.28_1.0.0_ga, smarc-imx_3.10.53_1.1.0_ga, smarc-imx_3.14.28_1.0.0_ga, smarc-l5.0.0_1.0.0-ga

atomic: only take lock when the counter drops to zero on UP as well 

_atomic_dec_and_lock() should not unconditionally take the lock before
calling atomic_dec_and_test() in the UP case.  For consistency reasons it
should behave exactly like in the SMP case.

Besides that this works around the problem that with CONFIG_DEBUG_SPINLOCK
this spins in __spin_lock_debug() if the lock is already taken even if the
counter doesn't drop to 0.

Signed-off-by: Jan Blunck <jblunck@suse.de>
Acked-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Acked-by: Nick Piggin <npiggin@suse.de>
Cc: Valerie Aurora <vaurora@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Showing 1 changed file with 1 additions and 2 deletions Side-by-side Diff

... ... @@ -19,11 +19,10 @@
19 19 */
20 20 int _atomic_dec_and_lock(atomic_t *atomic, spinlock_t *lock)
21 21 {
22   -#ifdef CONFIG_SMP
23 22 /* Subtract 1 from counter unless that drops it to 0 (ie. it was 1) */
24 23 if (atomic_add_unless(atomic, -1, 1))
25 24 return 0;
26   -#endif
  25 +
27 26 /* Otherwise do it the slow way */
28 27 spin_lock(lock);
29 28 if (atomic_dec_and_test(atomic))