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From: Jerome Brunet <jbrunet@baylibre.com>
To: Jassi Brar <jassisinghbrar@gmail.com>
Cc: Jerome Brunet <jbrunet@baylibre.com>,
	Kevin Hilman <khilman@baylibre.com>,
	linux-amlogic@lists.infradead.org, linux-kernel@vger.kernel.org,
	Da Xue <da@libre.computer>
Subject: [PATCH] mailbox: cancel timer before starting it
Date: Wed, 23 Sep 2020 14:39:16 +0200	[thread overview]
Message-ID: <20200923123916.1115962-1-jbrunet@baylibre.com> (raw)

If the txdone is done by polling, it is possible for msg_submit() to start
the timer while txdone_hrtimer() callback is running. If the timer needs
recheduling, it could already be enqueued by the time hrtimer_forward_now()
is called, leading hrtimer to loudly complain.

WARNING: CPU: 3 PID: 74 at kernel/time/hrtimer.c:932 hrtimer_forward+0xc4/0x110
CPU: 3 PID: 74 Comm: kworker/u8:1 Not tainted 5.9.0-rc2-00236-gd3520067d01c-dirty #5
Hardware name: Libre Computer AML-S805X-AC (DT)
Workqueue: events_freezable_power_ thermal_zone_device_check
pstate: 20000085 (nzCv daIf -PAN -UAO BTYPE=--)
pc : hrtimer_forward+0xc4/0x110
lr : txdone_hrtimer+0xf8/0x118
[...]

Canceling the timer before starting it ensure that the timer callback is
not running when the timer is started, solving this race condition.

Fixes: 0cc67945ea59 ("mailbox: switch to hrtimer for tx_complete polling")
Reported-by: Da Xue <da@libre.computer>
Signed-off-by: Jerome Brunet <jbrunet@baylibre.com>
---
 drivers/mailbox/mailbox.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/mailbox/mailbox.c b/drivers/mailbox/mailbox.c
index 0b821a5b2db8..34f9ab01caef 100644
--- a/drivers/mailbox/mailbox.c
+++ b/drivers/mailbox/mailbox.c
@@ -82,9 +82,13 @@ static void msg_submit(struct mbox_chan *chan)
 exit:
 	spin_unlock_irqrestore(&chan->lock, flags);
 
-	if (!err && (chan->txdone_method & TXDONE_BY_POLL))
-		/* kick start the timer immediately to avoid delays */
+	if (!err && (chan->txdone_method & TXDONE_BY_POLL)) {
+		/* Disable the timer if already active ... */
+		hrtimer_cancel(&chan->mbox->poll_hrt);
+
+		/* ... and kick start it immediately to avoid delays */
 		hrtimer_start(&chan->mbox->poll_hrt, 0, HRTIMER_MODE_REL);
+	}
 }
 
 static void tx_tick(struct mbox_chan *chan, int r)
-- 
2.25.4


WARNING: multiple messages have this Message-ID (diff)
From: Jerome Brunet <jbrunet@baylibre.com>
To: Jassi Brar <jassisinghbrar@gmail.com>
Cc: Kevin Hilman <khilman@baylibre.com>,
	linux-amlogic@lists.infradead.org, Da Xue <da@libre.computer>,
	linux-kernel@vger.kernel.org,
	Jerome Brunet <jbrunet@baylibre.com>
Subject: [PATCH] mailbox: cancel timer before starting it
Date: Wed, 23 Sep 2020 14:39:16 +0200	[thread overview]
Message-ID: <20200923123916.1115962-1-jbrunet@baylibre.com> (raw)

If the txdone is done by polling, it is possible for msg_submit() to start
the timer while txdone_hrtimer() callback is running. If the timer needs
recheduling, it could already be enqueued by the time hrtimer_forward_now()
is called, leading hrtimer to loudly complain.

WARNING: CPU: 3 PID: 74 at kernel/time/hrtimer.c:932 hrtimer_forward+0xc4/0x110
CPU: 3 PID: 74 Comm: kworker/u8:1 Not tainted 5.9.0-rc2-00236-gd3520067d01c-dirty #5
Hardware name: Libre Computer AML-S805X-AC (DT)
Workqueue: events_freezable_power_ thermal_zone_device_check
pstate: 20000085 (nzCv daIf -PAN -UAO BTYPE=--)
pc : hrtimer_forward+0xc4/0x110
lr : txdone_hrtimer+0xf8/0x118
[...]

Canceling the timer before starting it ensure that the timer callback is
not running when the timer is started, solving this race condition.

Fixes: 0cc67945ea59 ("mailbox: switch to hrtimer for tx_complete polling")
Reported-by: Da Xue <da@libre.computer>
Signed-off-by: Jerome Brunet <jbrunet@baylibre.com>
---
 drivers/mailbox/mailbox.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/mailbox/mailbox.c b/drivers/mailbox/mailbox.c
index 0b821a5b2db8..34f9ab01caef 100644
--- a/drivers/mailbox/mailbox.c
+++ b/drivers/mailbox/mailbox.c
@@ -82,9 +82,13 @@ static void msg_submit(struct mbox_chan *chan)
 exit:
 	spin_unlock_irqrestore(&chan->lock, flags);
 
-	if (!err && (chan->txdone_method & TXDONE_BY_POLL))
-		/* kick start the timer immediately to avoid delays */
+	if (!err && (chan->txdone_method & TXDONE_BY_POLL)) {
+		/* Disable the timer if already active ... */
+		hrtimer_cancel(&chan->mbox->poll_hrt);
+
+		/* ... and kick start it immediately to avoid delays */
 		hrtimer_start(&chan->mbox->poll_hrt, 0, HRTIMER_MODE_REL);
+	}
 }
 
 static void tx_tick(struct mbox_chan *chan, int r)
-- 
2.25.4


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linux-amlogic@lists.infradead.org
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             reply	other threads:[~2020-09-23 12:39 UTC|newest]

Thread overview: 36+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-09-23 12:39 Jerome Brunet [this message]
2020-09-23 12:39 ` [PATCH] mailbox: cancel timer before starting it Jerome Brunet
2020-09-24 16:50 ` Kevin Hilman
2020-09-24 16:50   ` Kevin Hilman
2020-10-15 13:46 ` Ionela Voinescu
2020-10-15 13:46   ` Ionela Voinescu
2020-10-15 13:58   ` Jerome Brunet
2020-10-15 13:58     ` Jerome Brunet
2020-10-15 14:29     ` Ionela Voinescu
2020-10-15 14:29       ` Ionela Voinescu
2020-10-16  8:44       ` Sudeep Holla
2020-10-16  8:44         ` Sudeep Holla
2020-10-16  9:02         ` Jerome Brunet
2020-10-16  9:02           ` Jerome Brunet
2020-10-16  9:34           ` Sudeep Holla
2020-10-16  9:34             ` Sudeep Holla
2020-10-16 11:47             ` Sudeep Holla
2020-10-16 11:47               ` Sudeep Holla
2020-10-15 18:45     ` Jassi Brar
2020-10-15 18:45       ` Jassi Brar
2020-10-16  8:52       ` Ionela Voinescu
2020-10-16  8:52         ` Ionela Voinescu
2020-10-16  9:00         ` Jerome Brunet
2020-10-16  9:00           ` Jerome Brunet
2020-10-16 13:52           ` Sudeep Holla
2020-10-16 13:52             ` Sudeep Holla
2020-10-16 17:33           ` Jassi Brar
2020-10-16 17:33             ` Jassi Brar
2020-10-16 18:54             ` Jerome Brunet
2020-10-16 18:54               ` Jerome Brunet
2020-10-16 19:27               ` Jassi Brar
2020-10-16 19:27                 ` Jassi Brar
2022-07-19  7:08                 ` Da Xue
2022-07-19  7:08                   ` Da Xue
2020-10-16 11:52         ` Sudeep Holla
2020-10-16 11:52           ` Sudeep Holla

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