From: Avi Kivity <avi@redhat.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>,
linux-kernel@vger.kernel.org, aarcange@redhat.com,
akpm@linux-foundation.org,
Kent Overstreet <kent.overstreet@gmail.com>,
Ingo Molnar <mingo@elte.hu>, tglx <tglx@linutronix.de>
Subject: Re: [COUNTERPATCH] mm: avoid overflowing preempt_count() in mmu_take_all_locks()
Date: Thu, 01 Apr 2010 14:09:30 +0300 [thread overview]
Message-ID: <4BB47EEA.4070102@redhat.com> (raw)
In-Reply-To: <1270117906.1653.139.camel@laptop>
On 04/01/2010 01:31 PM, Peter Zijlstra wrote:
> I'm sure you dropped Ingo and Thomas by accident.
>
> On Thu, 2010-04-01 at 12:40 +0300, Avi Kivity wrote:
>
>> mmu_take_all_locks() takes a spinlock for each vma, which means we increase
>> the preempt count by the number of vmas in an address space. Since the user
>> controls the number of vmas, they can cause preempt_count to overflow.
>>
>> Fix by making mmu_take_all_locks() only disable preemption once by making
>> the spinlocks preempt-neutral.
>>
> Right, so while this will get rid of the warning it doesn't make the
> code any nicer, its still a massive !preempt latency spot.
>
True. But this is a band-aid we can apply now while the correct fix is
being worked out.
--
error compiling committee.c: too many arguments to function
prev parent reply other threads:[~2010-04-01 11:10 UTC|newest]
Thread overview: 43+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-03-30 17:36 [PATCH] increase PREEMPT_BITS to 12 to avoid overflow when starting KVM Rik van Riel
2010-03-30 17:56 ` Peter Zijlstra
2010-03-30 18:05 ` Rik van Riel
2010-03-30 18:34 ` Peter Zijlstra
2010-04-01 9:40 ` [COUNTERPATCH] mm: avoid overflowing preempt_count() in mmu_take_all_locks() Avi Kivity
2010-04-01 10:31 ` Peter Zijlstra
2010-04-01 11:04 ` Thomas Gleixner
2010-04-01 11:13 ` Avi Kivity
2010-04-01 11:16 ` Peter Zijlstra
2010-04-01 11:19 ` Avi Kivity
2010-04-01 15:36 ` Andrea Arcangeli
2010-04-01 15:39 ` Avi Kivity
2010-04-01 15:54 ` Andrea Arcangeli
2010-04-01 16:02 ` Avi Kivity
2010-04-01 16:12 ` Andrea Arcangeli
2010-04-01 11:17 ` Avi Kivity
2010-04-01 11:27 ` Peter Zijlstra
2010-04-01 11:43 ` Peter Zijlstra
2010-04-01 11:47 ` Avi Kivity
2010-04-01 15:42 ` Andrea Arcangeli
2010-04-01 15:50 ` Peter Zijlstra
2010-04-01 15:56 ` Peter Zijlstra
2010-04-01 16:07 ` Andrea Arcangeli
2010-04-01 16:32 ` Peter Zijlstra
2010-04-01 16:00 ` Andrea Arcangeli
2010-04-01 15:51 ` Avi Kivity
2010-04-01 15:56 ` Peter Zijlstra
2010-04-01 16:06 ` Avi Kivity
2010-04-01 16:15 ` Paul E. McKenney
2010-04-01 16:36 ` Peter Zijlstra
2010-04-01 17:02 ` Paul E. McKenney
2010-04-01 16:08 ` Andrea Arcangeli
2010-04-01 16:14 ` Paul E. McKenney
2010-04-01 16:02 ` Andrea Arcangeli
2010-04-01 16:12 ` Peter Zijlstra
2010-04-01 16:18 ` Andrea Arcangeli
2010-04-01 16:45 ` Peter Zijlstra
2010-04-01 16:49 ` Peter Zijlstra
2010-04-01 17:04 ` Andrea Arcangeli
2010-04-01 14:16 ` Rik van Riel
2010-04-01 15:32 ` Andrea Arcangeli
2010-04-01 15:37 ` Avi Kivity
2010-04-01 11:09 ` Avi Kivity [this message]
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