linux-kernel - Re: [PATCH 3/3] cpufreq, powernow-k7: Fix double invocation of cpufreq_freq_transition

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Message-ID: <CAKohpo=RP-i9L4rNmQh=vEsXT5bEbXNQU1+bo7=gHZ4kLut9nA@mail.gmail.com>
Date:	Fri, 25 Apr 2014 13:54:52 +0530
From:	Viresh Kumar <viresh.kumar@...aro.org>
To:	"Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>
Cc:	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Meelis Roos <mroos@...ux.ee>,
	"cpufreq@...r.kernel.org" <cpufreq@...r.kernel.org>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 3/3] cpufreq, powernow-k7: Fix double invocation of cpufreq_freq_transition_begin/end

On 25 April 2014 13:48, Srivatsa S. Bhat
<srivatsa.bhat@...ux.vnet.ibm.com> wrote:
> During frequency transitions, the cpufreq core takes the responsibility of
> invoking cpufreq_freq_transition_begin() and cpufreq_freq_transition_end()
> for those cpufreq drivers that define the ->target_index callback but don't
> set the ASYNC_NOTIFICATION flag.
>
> The powernow-k7 cpufreq driver falls under this category, but this driver was
> invoking the _begin() and _end() APIs itself around frequency transitions,
> which led to double invocation of the _begin() API. The _begin API makes
> contending callers wait until the previous invocation is complete. Hence,
> the powernow-k7 driver ended up waiting on itself, leading to system hangs
> during boot.
>
> Fix this by removing the calls to the _begin() and _end() APIs from the
> powernow-k7 driver, since they rightly belong to the cpufreq core.
>
> Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@...ux.vnet.ibm.com>
> ---
>
>  drivers/cpufreq/powernow-k7.c |    4 ----
>  1 file changed, 4 deletions(-)

Acked-by: Viresh Kumar <viresh.kumar@...aro.org>
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