Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > linux.kernel > #1353109

[PATCH] mm: slub: Ensure that slab_unlock() is atomic

Show all headers | View raw

We observed livelocks on ARC SMP setup when running hackbench with SLUB.
This hardware configuration lacks atomic instructions (LLOCK/SCOND) thus
kernel resorts to a central @smp_bitops_lock to protect any R-M-W ops
suh as test_and_set_bit()

The spinlock itself is implemented using Atomic [EX]change instruction
which is always available.

The race happened when both cores tried to slab_lock() the same page.

   c1		    c0
-----------	-----------
slab_lock
		slab_lock
slab_unlock
		Not observing the unlock

This in turn happened because slab_unlock() doesn't serialize properly
(doesn't use atomic clear) with a concurrent running
slab_lock()->test_and_set_bit()

Cc: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Noam Camus <noamc@ezchip.com>
Cc: <stable@vger.kernel.org>
Cc: <linux-mm@kvack.org>
Cc: <linux-kernel@vger.kernel.org>
Cc: <linux-snps-arc@lists.infradead.org>
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
---
 mm/slub.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/slub.c b/mm/slub.c
index d8fbd4a6ed59..b7d345a508dc 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -345,7 +345,7 @@ static __always_inline void slab_lock(struct page *page)
 static __always_inline void slab_unlock(struct page *page)
 {
 	VM_BUG_ON_PAGE(PageTail(page), page);
-	__bit_spin_unlock(PG_locked, &page->flags);
+	bit_spin_unlock(PG_locked, &page->flags);
 }
 
 static inline void set_page_slub_counters(struct page *page, unsigned long counters_new)
-- 
2.5.0

Back to linux.kernel | Previous | Next — Next in thread | Find similar | Unroll thread

Thread

[PATCH] mm: slub: Ensure that slab_unlock() is atomic Vineet Gupta <Vineet.Gupta1@synopsys.com> - 2016-03-08 15:40 +0100
  Re: [PATCH] mm: slub: Ensure that slab_unlock() is atomic Christoph Lameter <cl@linux.com> - 2016-03-08 16:10 +0100
    Re: [PATCH] mm: slub: Ensure that slab_unlock() is atomic Vineet Gupta <vgupta@synopsys.com> - 2016-03-08 16:50 +0100
      Re: [PATCH] mm: slub: Ensure that slab_unlock() is atomic Christoph Lameter <cl@linux.com> - 2016-03-08 21:50 +0100
        Re: [PATCH] mm: slub: Ensure that slab_unlock() is atomic Vineet Gupta <Vineet.Gupta1@synopsys.com> - 2016-03-09 07:50 +0100
          Re: [PATCH] mm: slub: Ensure that slab_unlock() is atomic Peter Zijlstra <peterz@infradead.org> - 2016-03-09 11:20 +0100
            Re: [PATCH] mm: slub: Ensure that slab_unlock() is atomic Peter Zijlstra <peterz@infradead.org> - 2016-03-09 11:40 +0100
              Re: [PATCH] mm: slub: Ensure that slab_unlock() is atomic Vineet Gupta <Vineet.Gupta1@synopsys.com> - 2016-03-09 12:20 +0100
            Re: [PATCH] mm: slub: Ensure that slab_unlock() is atomic Vineet Gupta <Vineet.Gupta1@synopsys.com> - 2016-03-09 12:10 +0100
              Re: [PATCH] mm: slub: Ensure that slab_unlock() is atomic Peter Zijlstra <peterz@infradead.org> - 2016-03-09 12:50 +0100
                Re: [PATCH] mm: slub: Ensure that slab_unlock() is atomic Vineet Gupta <Vineet.Gupta1@synopsys.com> - 2016-03-09 13:00 +0100
                Re: [PATCH] mm: slub: Ensure that slab_unlock() is atomic Peter Zijlstra <peterz@infradead.org> - 2016-03-09 13:30 +0100
                Re: [PATCH] mm: slub: Ensure that slab_unlock() is atomic Vineet Gupta <Vineet.Gupta1@synopsys.com> - 2016-03-14 09:10 +0100
            Re: [PATCH] mm: slub: Ensure that slab_unlock() is atomic Vineet Gupta <Vineet.Gupta1@synopsys.com> - 2016-03-09 14:30 +0100
              Re: [PATCH] mm: slub: Ensure that slab_unlock() is atomic Peter Zijlstra <peterz@infradead.org> - 2016-03-09 16:00 +0100
                Re: [PATCH] mm: slub: Ensure that slab_unlock() is atomic Vineet Gupta <Vineet.Gupta1@synopsys.com> - 2016-03-10 07:00 +0100
                Re: [PATCH] mm: slub: Ensure that slab_unlock() is atomic Peter Zijlstra <peterz@infradead.org> - 2016-03-10 10:20 +0100
  Re: [PATCH] mm: slub: Ensure that slab_unlock() is atomic Vlastimil Babka <vbabka@suse.cz> - 2016-03-08 16:40 +0100

csiph-web