linux-kernel - [PATCH 2/8] PM / domains: Protect reading loop over list of domains

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Date:   Fri,  9 Jun 2017 18:08:47 +0200
From:   Krzysztof Kozlowski <krzk@...nel.org>
To:     "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Kevin Hilman <khilman@...nel.org>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        Pavel Machek <pavel@....cz>, Len Brown <len.brown@...el.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     Krzysztof Kozlowski <krzk@...nel.org>
Subject: [PATCH 2/8] PM / domains: Protect reading loop over list of domains

The pm_genpd_present() iterates over list of domains so grabbing a
gpd_list_lock mutex is necessary before calling it.  Otherwise we could
end up in iterating over and modifying the list at the same time.

Signed-off-by: Krzysztof Kozlowski <krzk@...nel.org>
---
 drivers/base/power/domain.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/base/power/domain.c b/drivers/base/power/domain.c
index 2e8d0f423507..2a6935dc0164 100644
--- a/drivers/base/power/domain.c
+++ b/drivers/base/power/domain.c
@@ -1099,8 +1099,13 @@ static void genpd_syscore_switch(struct device *dev, bool suspend)
 	struct generic_pm_domain *genpd;
 
 	genpd = dev_to_genpd(dev);
-	if (!pm_genpd_present(genpd))
+
+	mutex_lock(&gpd_list_lock);
+	if (!pm_genpd_present(genpd)) {
+		mutex_unlock(&gpd_list_lock);
 		return;
+	}
+	mutex_unlock(&gpd_list_lock);
 
 	if (suspend) {
 		genpd->suspended_count++;
-- 
2.9.3