linux-kernel - [PATCH 4.9 115/151] cpufreq: Skip cpufreq resume if its not suspended

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Message-Id: <20191127203044.013113893@linuxfoundation.org>
Date:   Wed, 27 Nov 2019 21:31:38 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Bo Yan <byan@...dia.com>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
        Lee Jones <lee.jones@...aro.org>
Subject: [PATCH 4.9 115/151] cpufreq: Skip cpufreq resume if its not suspended

From: Bo Yan <byan@...dia.com>

commit 703cbaa601ff3fb554d1246c336ba727cc083ea0 upstream.

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;

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@...dia.com>
Acked-by: Viresh Kumar <viresh.kumar@...aro.org>
[ rjw: Dropped printing a message ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
Signed-off-by: Lee Jones <lee.jones@...aro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/cpufreq/cpufreq.c |    3 +++
 1 file changed, 3 insertions(+)

--- a/drivers/cpufreq/cpufreq.c
+++ b/drivers/cpufreq/cpufreq.c
@@ -1646,6 +1646,9 @@ void cpufreq_resume(void)
 	if (!cpufreq_driver)
 		return;

+	if (unlikely(!cpufreq_suspended))
+		return;
+
 	cpufreq_suspended = false;

 	if (!has_target() && !cpufreq_driver->resume)