linux-kernel - Re: [PATCH]: Use stop_machine

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Message-ID: <45E42268.30209@redhat.com>
Date:	Tue, 27 Feb 2007 07:22:00 -0500
From:	Prarit Bhargava <prarit@...hat.com>
To:	Prarit Bhargava <prarit@...hat.com>
CC:	linux-kernel@...r.kernel.org, akpm@...ux-foundation.org,
	jbeulich@...ell.com, anil.s.keshavamurthy@...el.com,
	amul.shah@...sys.com
Subject: Re: [PATCH]: Use stop_machine_run in the Intel RNG driver



Prarit Bhargava wrote:
> Replace call_smp_function with stop_machine_run in the Intel RNG driver.
>
> CPU A has done read_lock(&lock)
> CPU B has done write_lock_irq(&lock) and is waiting for A to release the lock.
>
> A third CPU calls call_smp_function and issues the IPI.  CPU A takes CPU C's
> IPI.  CPU B is waiting with interrupts disabled and does not see the IPI.
> CPU C is stuck waiting for CPU B to respond to the IPI.
>
> Deadlock.
>
> The solution is to use stop_machine_run instead of call_smp_function
> (call_smp_function should not be called in situations where the CPUs may
> be suspended).
>
>
>   

Updated patch to latest-and-greatest git ...

P.


View attachment "intel-rng.patch" of type "text/plain" (10014 bytes)