linux-kernel - Re: [PATCH] [CPUFREQ] fix race condition in store_scaling

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Message-ID: <4BED2A7D.1070801@udo.edu>
Date:	Fri, 14 May 2010 12:48:29 +0200
From:	Andrej Gelenberg <andrej.gelenberg@....edu>
To:	Américo Wang <xiyou.wangcong@...il.com>
CC:	linux@...do.de, ashok.raj@...el.com, jacob.shin@....com,
	linux-kernel@...r.kernel.org, akpm@...ux-foundation.org
Subject: Re: [PATCH] [CPUFREQ] fix race condition in store_scaling_governor

Hi,

i found the cause for the bug: it was commit "[CPUFREQ] remove rwsem 
lock from CPUFREQ_GOV_STOP call (second call site)".
It release the rwsem lock in the middle of __cpufreq_set_policy, that is 
not a good idea. There are no dead lock, which that patch solved,
because cpufreq_ondemand and cpufreq_conservative don't use the rwsem
lock in do_dbs_timer anymore.

Regards,
Andrej Gelenberg

View attachment "0001-CPUFREQ-Revert-CPUFREQ-remove-rwsem-lock-from-CPUFRE.patch" of type "text/plain" (1431 bytes)