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authorViresh Kumar <viresh.kumar@linaro.org>2017-09-21 10:44:36 -0700
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2017-10-05 09:47:35 +0200
commit5bf264461b2a45d28cdc1ba90ffa9bd52e667d2c (patch)
tree481190c86fb56cdd8b1e200a0206b535e7490331
parent211d5eabde61c1d7759b98f1b101abd35b330e28 (diff)
PM / OPP: Call notifier without holding opp_table->lock
commit e4d8ae00169f7686e1da5a62e5cf797d12bf8822 upstream. The notifier callbacks may want to call some OPP helper routines which may try to take the same opp_table->lock again and cause a deadlock. One such usecase was reported by Chanwoo Choi, where calling dev_pm_opp_disable() leads us to the devfreq's OPP notifier handler, which further calls dev_pm_opp_find_freq_floor() and it deadlocks. We don't really need the opp_table->lock to be held across the notifier call though, all we want to make sure is that the 'opp' doesn't get freed while being used from within the notifier chain. We can do it with help of dev_pm_opp_get/put() as well. Let's do it. Fixes: 5b650b388844 "PM / OPP: Take kref from _find_opp_table()" Reported-by: Chanwoo Choi <cw00.choi@samsung.com> Tested-by: Chanwoo Choi <cw00.choi@samsung.com> Reviewed-by: Stephen Boyd <sboyd@codeaurora.org> Reviewed-by: Chanwoo Choi <cw00.choi@samsung.com> Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--drivers/base/power/opp/core.c7
1 files changed, 7 insertions, 0 deletions
diff --git a/drivers/base/power/opp/core.c b/drivers/base/power/opp/core.c
index a8cc14fd8ae4..a6de32530693 100644
--- a/drivers/base/power/opp/core.c
+++ b/drivers/base/power/opp/core.c
@@ -1581,6 +1581,9 @@ static int _opp_set_availability(struct device *dev, unsigned long freq,
opp->available = availability_req;
+ dev_pm_opp_get(opp);
+ mutex_unlock(&opp_table->lock);
+
/* Notify the change of the OPP availability */
if (availability_req)
blocking_notifier_call_chain(&opp_table->head, OPP_EVENT_ENABLE,
@@ -1589,8 +1592,12 @@ static int _opp_set_availability(struct device *dev, unsigned long freq,
blocking_notifier_call_chain(&opp_table->head,
OPP_EVENT_DISABLE, opp);
+ dev_pm_opp_put(opp);
+ goto put_table;
+
unlock:
mutex_unlock(&opp_table->lock);
+put_table:
dev_pm_opp_put_opp_table(opp_table);
return r;
}