From: Christoph Lameter <cl@linux.com>
To: Vineet Gupta <vgupta@synopsys.com>
Cc: linux-mm@kvack.org, Pekka Enberg <penberg@kernel.org>,
David Rientjes <rientjes@google.com>,
Joonsoo Kim <iamjoonsoo.kim@lge.com>,
Andrew Morton <akpm@linux-foundation.org>,
Noam Camus <noamc@ezchip.com>,
stable@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-snps-arc@lists.infradead.org
Subject: Re: [PATCH] mm: slub: Ensure that slab_unlock() is atomic
Date: Tue, 8 Mar 2016 14:40:52 -0600 (CST) [thread overview]
Message-ID: <alpine.DEB.2.20.1603081438020.4268@east.gentwo.org> (raw)
In-Reply-To: <56DEF3D3.6080008@synopsys.com>
On Tue, 8 Mar 2016, Vineet Gupta wrote:
> # set the bit
> 80543b8e: ld_s r2,[r13,0] <--- (A) Finds PG_locked is set
> 80543b90: or r3,r2,1 <--- (B) other core unlocks right here
> 80543b94: st_s r3,[r13,0] <--- (C) sets PG_locked (overwrites unlock)
Duh. Guess you need to take the spinlock also in the arch specific
implementation of __bit_spin_unlock(). This is certainly not the only case
in which we use the __ op to unlock.
You need a true atomic op or you need to take the "spinlock" in all
cases where you modify the bit. If you take the lock in __bit_spin_unlock
then the race cannot happen.
> Are you convinced now !
Yes, please fix your arch specific code.
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next prev parent reply other threads:[~2016-03-08 20:40 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-03-08 14:30 Vineet Gupta
2016-03-08 15:00 ` Christoph Lameter
2016-03-08 15:46 ` Vineet Gupta
2016-03-08 20:40 ` Christoph Lameter [this message]
2016-03-09 6:43 ` Vineet Gupta
2016-03-09 10:13 ` Peter Zijlstra
2016-03-09 10:31 ` Peter Zijlstra
2016-03-09 11:12 ` Vineet Gupta
2016-03-09 11:00 ` Vineet Gupta
2016-03-09 11:40 ` Peter Zijlstra
2016-03-09 11:53 ` Vineet Gupta
2016-03-09 12:22 ` Peter Zijlstra
2016-03-14 8:05 ` Vineet Gupta
2016-03-09 13:22 ` Vineet Gupta
2016-03-09 14:51 ` Peter Zijlstra
2016-03-10 5:51 ` Vineet Gupta
2016-03-10 9:10 ` Peter Zijlstra
2016-03-08 15:32 ` Vlastimil Babka
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