linux-kernel - [PATCHv3] bq2415x_charger: Fix Atomic Sleep Bug

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Message-Id: <1396869244-1000-1-git-send-email-sre@kernel.org>
Date:	Mon,  7 Apr 2014 13:14:04 +0200
From:	Sebastian Reichel <sre@...nel.org>
To:	Sebastian Reichel <sre@...g0.de>,
	Dmitry Eremin-Solenikov <dbaryshkov@...il.com>,
	David Woodhouse <dwmw2@...radead.org>
Cc:	Pali Rohár <pali.rohar@...il.com>,
	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Sebastian Reichel <sre@...nel.org>
Subject: [PATCHv3] bq2415x_charger: Fix Atomic Sleep Bug

Move sysfs_notify and i2c_transfer calls from bq2415x_notifier_call
to bq2415x_timer_work to avoid sleeping in atomic context.

This fixes the following bug:

[ 7.667449] Workqueue: events power_supply_changed_work
[ 7.673034] [<c0015c28>] (unwind_backtrace+0x0/0xe0) from [<c0011e1c>] (show_stack+0x10/0x14)
[ 7.682098] [<c0011e1c>] (show_stack+0x10/0x14) from [<c052cdd0>] (dump_stack+0x78/0xac)
[ 7.690704] [<c052cdd0>] (dump_stack+0x78/0xac) from [<c052a044>] (__schedule_bug+0x48/0x60)
[ 7.699645] [<c052a044>] (__schedule_bug+0x48/0x60) from [<c053071c>] (__schedule+0x74/0x638)
[ 7.708618] [<c053071c>] (__schedule+0x74/0x638) from [<c05301fc>] (schedule_timeout+0x1dc/0x24c)
[ 7.718017] [<c05301fc>] (schedule_timeout+0x1dc/0x24c) from [<c05316ec>] (wait_for_common+0x138/0x17c)
[ 7.727966] [<c05316ec>] (wait_for_common+0x138/0x17c) from [<c0362a70>] (omap_i2c_xfer+0x340/0x4a0)
[ 7.737640] [<c0362a70>] (omap_i2c_xfer+0x340/0x4a0) from [<c035d928>] (__i2c_transfer+0x40/0x74)
[ 7.747039] [<c035d928>] (__i2c_transfer+0x40/0x74) from [<c035e22c>] (i2c_transfer+0x6c/0x90)
[ 7.756195] [<c035e22c>] (i2c_transfer+0x6c/0x90) from [<c037ad24>] (bq2415x_i2c_write+0x48/0x78)
[ 7.765563] [<c037ad24>] (bq2415x_i2c_write+0x48/0x78) from [<c037ae60>] (bq2415x_set_weak_battery_voltage+0x4c/0x50)
[ 7.776824] [<c037ae60>] (bq2415x_set_weak_battery_voltage+0x4c/0x50) from [<c037bce8>] (bq2415x_set_mode+0xdc/0x14c)
[ 7.788085] [<c037bce8>] (bq2415x_set_mode+0xdc/0x14c) from [<c037bfb8>] (bq2415x_notifier_call+0xa8/0xb4)
[ 7.798309] [<c037bfb8>] (bq2415x_notifier_call+0xa8/0xb4) from [<c005f228>] (notifier_call_chain+0x38/0x68)
[ 7.808715] [<c005f228>] (notifier_call_chain+0x38/0x68) from [<c005f284>] (__atomic_notifier_call_chain+0x2c/0x3c)
[ 7.819732] [<c005f284>] (__atomic_notifier_call_chain+0x2c/0x3c) from [<c005f2a8>] (atomic_notifier_call_chain+0x14/0x18)
[ 7.831420] [<c005f2a8>] (atomic_notifier_call_chain+0x14/0x18) from [<c0378078>] (power_supply_changed_work+0x6c/0xb8)
[ 7.842864] [<c0378078>] (power_supply_changed_work+0x6c/0xb8) from [<c00556c0>] (process_one_work+0x248/0x440)
[ 7.853546] [<c00556c0>] (process_one_work+0x248/0x440) from [<c0055d6c>] (worker_thread+0x208/0x350)
[ 7.863372] [<c0055d6c>] (worker_thread+0x208/0x350) from [<c005b0ac>] (kthread+0xc8/0xdc)
[ 7.872131] [<c005b0ac>] (kthread+0xc8/0xdc) from [<c000e138>] (ret_from_fork+0x14/0x3c)

Signed-off-by: Sebastian Reichel <sre@...nel.org>
---
Hi,

I send this patch in February for 3.14-rc [0], but I never got a reply from
Dmitry or David. The last change in the power-supply git [1] was seven weeks
ago, so they seem to be too busy for kernel work at the moment.

But now the bug is in the 3.14 release (thus I added stable@ to the list of
receivers) and still a problem on HEAD with no sign of any pull request from
the power-supply subsystem.

Changes since PATCHv2:
 * Changed my e-mail address from @debian.org to @kernel.org

[0] https://lkml.org/lkml/2014/2/24/568
[1] http://git.infradead.org/battery-2.6.git/

-- Sebastian
---
 drivers/power/bq2415x_charger.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/power/bq2415x_charger.c b/drivers/power/bq2415x_charger.c
index 79a37f6..e384844 100644
--- a/drivers/power/bq2415x_charger.c
+++ b/drivers/power/bq2415x_charger.c
@@ -840,8 +840,7 @@ static int bq2415x_notifier_call(struct notifier_block *nb,
 	if (bq->automode < 1)
 		return NOTIFY_OK;
 
-	sysfs_notify(&bq->charger.dev->kobj, NULL, "reported_mode");
-	bq2415x_set_mode(bq, bq->reported_mode);
+	schedule_delayed_work(&bq->work, 0);
 
 	return NOTIFY_OK;
 }
@@ -892,6 +891,11 @@ static void bq2415x_timer_work(struct work_struct *work)
 	int error;
 	int boost;
 
+	if (bq->automode > 0 && (bq->reported_mode != bq->mode)) {
+		sysfs_notify(&bq->charger.dev->kobj, NULL, "reported_mode");
+		bq2415x_set_mode(bq, bq->reported_mode);
+	}
+
 	if (!bq->autotimer)
 		return;
 
-- 
1.9.1

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