Re: [RFC PATCH] sysrq: don't hold the sysrq_key_table_lock duringthe handler

From: Andrew Morton
Date: Tue Jul 27 2010 - 19:37:28 EST

On Mon, 26 Jul 2010 17:54:02 +0800
Xiaotian Feng <dfeng@xxxxxxxxxx> 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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