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: Miles Lane <miles.lane@gmail.com>
Signed-off-by: Nathan Lynch <ntl@pobox.com>
Signed-off-by: Bryan Wu <roc@roc-samos.(none)>

diff --git a/drivers/leds/ledtrig-cpu.c b/drivers/leds/ledtrig-cpu.c
index b312056..4239b39 100644 (file)
--- a/drivers/leds/ledtrig-cpu.c
+++ b/drivers/leds/ledtrig-cpu.c
@@ -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);