From: Ingo Molnar <mingo@elte.hu>
To: Mark Fasheh <mark.fasheh@oracle.com>
Cc: linux-kernel@vger.kernel.org, akpm@osdl.org,
jim.houston@ccur.com, sunil.mushran@oracle.com
Subject: Re: [PATCH] Conditionally check expected_preempt_count in __resched_legal()
Date: Wed, 13 Dec 2006 21:04:22 +0100 [thread overview]
Message-ID: <20061213200422.GA992@elte.hu> (raw)
In-Reply-To: <20061213195537.GH6831@ca-server1.us.oracle.com>
* Mark Fasheh <mark.fasheh@oracle.com> wrote:
> Commit 2d7d253548cffdce80f4e03664686e9ccb1b0ed7 ("fix cond_resched() fix")
> introduced an 'expected_preempt_count' parameter to __resched_legal() to fix
> a bug where it was returning a false negative when called from
> cond_resched_lock() and preemption was enabled.
>
> Unfortunately this broke things for when preemption is disabled.
> preempt_count() will always return zero, thus failing the check against
> any value of expected_preempt_count not equal to zero. cond_resched_lock()
> for example, passes an expected_preempt_count value of 1.
>
> So fix the fix for the cond_resched() fix by skipping the check of
> preempt_count() against expected_preempt_count when preemption is disabled.
>
> Credit should go to Sunil Mushran for spotting the bug during testing.
>
> Signed-off-by: Mark Fasheh <mark.fasheh@oracle.com>
well spotted. I'm wondering whether this piece of code has the highest
amount of fixes per line of code ratio in the whole kernel ...
Acked-by: Ingo Molnar <mingo@elte.hu>
Ingo
prev parent reply other threads:[~2006-12-13 20:06 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-12-13 19:55 [PATCH] Conditionally check expected_preempt_count in __resched_legal() Mark Fasheh
2006-12-13 20:04 ` Ingo Molnar [this message]
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