Commit 40da1b11 authored Jun 02, 2017 by Sebastian Andrzej Siewior Committed by Thomas Gleixner Jun 03, 2017

cpu/hotplug: Drop the device lock on error



If a custom CPU target is specified and that one is not available _or_
can't be interrupted then the code returns to userland without dropping a
lock as notices by lockdep:

|echo 133 > /sys/devices/system/cpu/cpu7/hotplug/target
| ================================================
| [ BUG: lock held when returning to user space! ]
| ------------------------------------------------
| bash/503 is leaving the kernel with locks still held!
| 1 lock held by bash/503:
|  #0:  (device_hotplug_lock){+.+...}, at: [<ffffffff815b5650>] lock_device_hotplug_sysfs+0x10/0x40

So release the lock then.

Fixes: 757c989b ("cpu/hotplug: Make target state writeable")
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: stable@vger.kernel.org
Link: http://lkml.kernel.org/r/20170602142714.3ogo25f2wbq6fjpj@linutronix.de

parent 104c08ba

kernel/cpu.c

+2 −2

Original line number	Diff line number	Diff line
		@@ -1658,13 +1658,13 @@ static ssize_t write_cpuhp_target(struct device *dev,
		ret = !sp->name \|\| sp->cant_stop ? -EINVAL : 0;
		mutex_unlock(&cpuhp_state_mutex);
		if (ret)
		return ret;
		goto out;

		if (st->state < target)
		ret = do_cpu_up(dev->id, target);
		else
		ret = do_cpu_down(dev->id, target);

		out:
		unlock_device_hotplug();
		return ret ? ret : count;
		}

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