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From: Viresh Kumar <viresh.kumar@linaro.org>
To: Viresh Kumar <vireshk@kernel.org>, Nishanth Menon <nm@ti.com>,
	Stephen Boyd <sboyd@kernel.org>
Cc: Viresh Kumar <viresh.kumar@linaro.org>,
	linux-pm@vger.kernel.org,
	Vincent Guittot <vincent.guittot@linaro.org>,
	Rafael Wysocki <rjw@rjwysocki.net>,
	Dmitry Osipenko <digetx@gmail.com>,
	linux-kernel@vger.kernel.org
Subject: [PATCH] opp: Reinitialize the list_kref before adding the static OPPs again
Date: Fri, 18 Oct 2019 14:58:41 +0530	[thread overview]
Message-ID: <2700308706c0d46ca06eeb973079a1f18bf553dd.1571390916.git.viresh.kumar@linaro.org> (raw)

The list_kref reaches a count of 0 when all the static OPPs are removed,
for example when dev_pm_opp_of_cpumask_remove_table() is called, though
the actual OPP table may not get freed as it may still be referenced by
other parts of the kernel, like from a call to
dev_pm_opp_set_supported_hw(). And if we call
dev_pm_opp_of_cpumask_add_table() again at this point, we must
reinitialize the list_kref otherwise the kernel will hit a WARN() in
kref infrastructure for incrementing a kref with value 0.

Fixes: 11e1a1648298 ("opp: Don't decrement uninitialized list_kref")
Reported-by: Dmitry Osipenko <digetx@gmail.com>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
---
 drivers/opp/of.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/opp/of.c b/drivers/opp/of.c
index 6dc41faf74b5..1cbb58240b80 100644
--- a/drivers/opp/of.c
+++ b/drivers/opp/of.c
@@ -663,6 +663,13 @@ static int _of_add_opp_table_v2(struct device *dev, struct opp_table *opp_table)
 		return 0;
 	}
 
+	/*
+	 * Re-initialize list_kref every time we add static OPPs to the OPP
+	 * table as the reference count may be 0 after the last tie static OPPs
+	 * were removed.
+	 */
+	kref_init(&opp_table->list_kref);
+
 	/* We have opp-table node now, iterate over it and add OPPs */
 	for_each_available_child_of_node(opp_table->np, np) {
 		opp = _opp_add_static_v2(opp_table, dev, np);
-- 
2.21.0.rc0.269.g1a574e7a288b


             reply	other threads:[~2019-10-18  9:28 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-10-18  9:28 Viresh Kumar [this message]
2019-10-18 15:35 ` [PATCH] opp: Reinitialize the list_kref before adding the static OPPs again Dmitry Osipenko
2019-10-21  2:18   ` Viresh Kumar
2019-10-18 21:12 ` Stephen Boyd
2019-10-21  2:25   ` Viresh Kumar
2019-10-28 12:01     ` Stephen Boyd
2019-10-30  7:50       ` Viresh Kumar
     [not found]         ` <20191030143400.1680D20656@mail.kernel.org>
2019-11-11  8:21           ` Viresh Kumar
2019-11-11 11:31             ` Viresh Kumar

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