@@ -1627,6 +1627,9 @@ 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,
@@ -1635,8 +1638,12 @@ 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;
}
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. Cc: 4.11+ <stable@vger.kernel.org> # 4.11+ Fixes: 5b650b388844 ("PM / OPP: Take kref from _find_opp_table()") Reported-by: Chanwoo Choi <cw00.choi@samsung.com> Reviewed-by: Stephen Boyd <sboyd@codeaurora.org> Reviewed-by: Chanwoo Choi <cw00.choi@samsung.com> Tested-by: Chanwoo Choi <cw00.choi@samsung.com> Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org> --- V2->V3: - Added fixes, Cc and tags from Chanwoo. drivers/base/power/opp/core.c | 7 +++++++ 1 file changed, 7 insertions(+) -- 2.7.4