From: "Rafael J. Wysocki" <rjw@rjwysocki.net>
To: Bo Yan <byan@nvidia.com>
Cc: viresh.kumar@linaro.org, sgurrappadi@nvidia.com,
linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] cpufreq: skip cpufreq resume if it's not suspended
Date: Mon, 05 Feb 2018 10:19:55 +0100 [thread overview]
Message-ID: <1563547.VDOW1Ixonm@aspire.rjw.lan> (raw)
In-Reply-To: <1516744675-21233-1-git-send-email-byan@nvidia.com>
On Tuesday, January 23, 2018 10:57:55 PM CET Bo Yan wrote:
> cpufreq_resume can be called even without preceding cpufreq_suspend.
> This can happen in following scenario:
>
> suspend_devices_and_enter
> --> dpm_suspend_start
> --> dpm_prepare
> --> device_prepare : this function errors out
> --> dpm_suspend: this is skipped due to dpm_prepare failure
> this means cpufreq_suspend is skipped over
> --> goto Recover_platform, due to previous error
> --> goto Resume_devices
> --> dpm_resume_end
> --> dpm_resume
> --> cpufreq_resume
>
> In case schedutil is used as frequency governor, cpufreq_resume will
> eventually call sugov_start, which does following:
>
> memset(sg_cpu, 0, sizeof(*sg_cpu));
> ....
>
> This effectively erases function pointer for frequency update, causing
> crash later on. The function pointer would have been set correctly if
> subsequent cpufreq_add_update_util_hook runs successfully, but that
> function returns earlier because cpufreq_suspend was not called:
>
> if (WARN_ON(per_cpu(cpufreq_update_util_data, cpu)))
> return;
>
> Ideally, suspend should succeed, then things will be fine. But even
> in case of suspend failure, system should not crash.
>
> The fix is to check cpufreq_suspended first, if it's false, that means
> cpufreq_suspend was not called in the first place, so do not resume
> cpufreq.
>
> Signed-off-by: Bo Yan <byan@nvidia.com>
> ---
> drivers/cpufreq/cpufreq.c | 4 ++++
> 1 file changed, 4 insertions(+)
>
> diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
> index 41d148af7748..95b1c4afe14e 100644
> --- a/drivers/cpufreq/cpufreq.c
> +++ b/drivers/cpufreq/cpufreq.c
> @@ -1680,6 +1680,10 @@ void cpufreq_resume(void)
> if (!cpufreq_driver)
> return;
>
> + if (unlikely(!cpufreq_suspended)) {
> + pr_warn("%s: resume after failing suspend\n", __func__);
> + return;
> + }
> cpufreq_suspended = false;
>
> if (!has_target() && !cpufreq_driver->resume)
I've just edited this patch somewhat (mostly by dropping the pr_warn())
and queued it up.
Thanks,
Rafael
next prev parent reply other threads:[~2018-02-05 9:22 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-01-23 21:57 [PATCH] cpufreq: skip cpufreq resume if it's not suspended Bo Yan
2018-01-24 2:02 ` Rafael J. Wysocki
2018-01-24 20:53 ` Bo Yan
2018-02-02 11:54 ` Rafael J. Wysocki
2018-02-02 19:34 ` Saravana Kannan
2018-02-02 21:28 ` Bo Yan
2018-02-05 4:01 ` Viresh Kumar
2018-02-05 8:50 ` Rafael J. Wysocki
2018-02-05 9:05 ` Viresh Kumar
2018-02-15 21:27 ` Saravana Kannan
2018-02-15 22:06 ` Rafael J. Wysocki
2018-01-25 19:15 ` [PATCH v2] " Bo Yan
2018-02-05 9:19 ` Rafael J. Wysocki [this message]
2018-02-05 9:23 ` [PATCH] " Viresh Kumar
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