Date: Tue, 27 Jul 2010 16:36:22 -0700
From: Andrew Morton <akpm@linux-foundation.org>
To: Xiaotian Feng <dfeng@redhat.com>
Cc: linux-kernel@vger.kernel.org, Ingo Molnar <mingo@elte.hu>,
        Dmitry Torokhov <dmitry.torokhov@gmail.com>,
        Neil Horman <nhorman@tuxdriver.com>,
        "David S. Miller" <davem@davemloft.net>
Subject: Re: [RFC PATCH] sysrq: don't hold the sysrq_key_table_lock during
 the handler
Message-Id: <20100727163622.a19a827b.akpm@linux-foundation.org>
In-Reply-To: <1280138042-1576-1-git-send-email-dfeng@redhat.com>
References: <1280138042-1576-1-git-send-email-dfeng@redhat.com>
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On Mon, 26 Jul 2010 17:54:02 +0800
Xiaotian Feng <dfeng@redhat.com> wrote:

> sysrq_key_table_lock is used to protect the sysrq_key_table, make sure
> we get/replace the right operation for the sysrq. But in __handle_sysrq,
> kernel will hold this lock and disable irqs until we finished op_p->handler().
> This may cause false positive watchdog alert when we're doing "show-task-states"
> on a system with many tasks.
> 

It would be better to find a suitable point in an inner loop and add an
appropriately-commented touch_nmi_watchdog().

That way the problem gets fixed for all irqs-off callers, not just one
of them.

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