From: Peter Zijlstra <peterz@infradead.org>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Nick Piggin <npiggin@suse.de>, Jens Axboe <jens.axboe@oracle.com>,
"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
Ingo Molnar <mingo@elte.hu>,
Rusty Russell <rusty@rustcorp.com.au>,
linux-kernel@vger.kernel.org, Oleg Nesterov <oleg@redhat.com>
Subject: Re: [PATCH 1.5/2] generic-smp: fix initial quiesent count.
Date: Sat, 14 Feb 2009 22:14:16 +0100 [thread overview]
Message-ID: <1234646056.4695.10.camel@laptop> (raw)
In-Reply-To: <1234622792.4698.31.camel@laptop>
On Sat, 2009-02-14 at 15:46 +0100, Peter Zijlstra wrote:
> first compile, then send out...
>
> ---
> Subject: generic-smp: fix initial quiesent count.
> From: Peter Zijlstra <a.p.zijlstra@chello.nl>
> Date: Sat Feb 14 15:36:07 CET 2009
>
> If we start with a quiesent sequence count of 0, we'll match the initial stamp
> values of the cfd_data, and never make any progress.
>
> To avoid getting stuck in this situation, start out with an increased quiesent
> sequence count.
OK, so this is not going to fix the problem in generic. Its still
possible to end up with the original issue.
We'd need a callback list to free used entries, much like regular RCU,
this quiesent sequence count's wrapping just seems too brittle.
next prev parent reply other threads:[~2009-02-14 21:17 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-02-12 22:32 [PATCH 0/2] generic smp helpers vs kmalloc Peter Zijlstra
2009-02-12 22:32 ` [PATCH 1/2] generic-smp: remove single ipi fallback for smp_call_function_many() Peter Zijlstra
2009-02-14 14:41 ` [PATCH 1.5/2] generic-smp: fix initial quiesent count Peter Zijlstra
2009-02-14 14:46 ` Peter Zijlstra
2009-02-14 21:14 ` Peter Zijlstra [this message]
2009-02-14 23:29 ` Ingo Molnar
2009-02-12 22:32 ` [PATCH 2/2] generic-smp: remove kmalloc usage Peter Zijlstra
2009-02-14 14:46 ` [PATCH 2.5/2] generic-smp: remove cfd rcu_head Peter Zijlstra
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