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Commit 0b8728d6 authored by Nathan Lynch's avatar Nathan Lynch Committed by Bryan Wu
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ledtrig-cpu: kill useless mutex to fix sleep in atomic context 



Seeing the following every time the CPU enters or leaves idle on a
Beagleboard:

BUG: sleeping function called from invalid context at kernel/mutex.c:269
in_atomic(): 1, irqs_disabled(): 0, pid: 0, name: swapper/0
no locks held by swapper/0/0.
[<c001659c>] (unwind_backtrace+0x0/0xf8) from [<c05aaa7c>] (mutex_lock_nested+0x24/0x380)
[<c05aaa7c>] (mutex_lock_nested+0x24/0x380) from [<c043bd1c>] (ledtrig_cpu+0x38/0x88)
[<c043bd1c>] (ledtrig_cpu+0x38/0x88) from [<c000f4b0>] (cpu_idle+0xf4/0x120)
[<c000f4b0>] (cpu_idle+0xf4/0x120) from [<c07e47c8>] (start_kernel+0x2bc/0x30c)

Miles Lane has reported seeing similar splats during system suspend.

The mutex in struct led_trigger_cpu appears to have no function: it
resides in a per-cpu data structure which never changes after the
trigger is registered.  So just remove it.

Reported-by: default avatarMiles Lane <miles.lane@gmail.com>
Signed-off-by: default avatarNathan Lynch <ntl@pobox.com>
Signed-off-by: default avatarBryan Wu <roc@roc-samos.(none)>
parent 77b67063

drivers/leds/ledtrig-cpu.c

+0 −21
Original line number Diff line number Diff line
@@ -33,8 +33,6 @@ 
struct led_trigger_cpu {

	char name[MAX_NAME_LEN];

	struct led_trigger *_trig;

	struct mutex lock;

	int lock_is_inited;

};



static DEFINE_PER_CPU(struct led_trigger_cpu, cpu_trig);
@@ -50,12 +48,6 @@ void ledtrig_cpu(enum cpu_led_event ledevt) 
{

	struct led_trigger_cpu *trig = &__get_cpu_var(cpu_trig);



	/* mutex lock should be initialized before calling mutex_call() */

	if (!trig->lock_is_inited)

		return;



	mutex_lock(&trig->lock);



	/* Locate the correct CPU LED */

	switch (ledevt) {

	case CPU_LED_IDLE_END:
@@ -75,8 +67,6 @@ void ledtrig_cpu(enum cpu_led_event ledevt) 
		/* Will leave the LED as it is */

		break;

	}



	mutex_unlock(&trig->lock);

}

EXPORT_SYMBOL(ledtrig_cpu);
@@ -117,14 +107,9 @@ static int __init ledtrig_cpu_init(void) 
	for_each_possible_cpu(cpu) {

		struct led_trigger_cpu *trig = &per_cpu(cpu_trig, cpu);



		mutex_init(&trig->lock);



		snprintf(trig->name, MAX_NAME_LEN, "cpu%d", cpu);



		mutex_lock(&trig->lock);

		led_trigger_register_simple(trig->name, &trig->_trig);

		trig->lock_is_inited = 1;

		mutex_unlock(&trig->lock);

	}



	register_syscore_ops(&ledtrig_cpu_syscore_ops);
@@ -142,15 +127,9 @@ static void __exit ledtrig_cpu_exit(void) 
	for_each_possible_cpu(cpu) {

		struct led_trigger_cpu *trig = &per_cpu(cpu_trig, cpu);



		mutex_lock(&trig->lock);



		led_trigger_unregister_simple(trig->_trig);

		trig->_trig = NULL;

		memset(trig->name, 0, MAX_NAME_LEN);

		trig->lock_is_inited = 0;



		mutex_unlock(&trig->lock);

		mutex_destroy(&trig->lock);

	}



	unregister_syscore_ops(&ledtrig_cpu_syscore_ops);