Linux内核Timer使用注意事项

在Timer Callback的调用中，不能出现上下文切换（比如mutex_lock之类的），否则会导致系统crash.

[    3.170017] [TC358743]hdmi_input_monitor_process into

[    3.175514] BUG: scheduling while atomic: swapper/1/0/0x00000103
[    3.182956] bad: scheduling from the idle thread!
[   72.010005] INFO: rcu_preempt self-detected stall on CPU
[   72.010005]  1: (1 GPs behind) idle=89b/2/0 @岍?
                                                    [   72.010005]       (t=6000 jiffies)
[   72.040016] INFO: rcu_preempt detected stalls on CPUs/tasks: 00000000
[   72.047299]  0: (1 GPs behind) idle=189/1/0 \}庢
[   72.050003]  1: (1 GPs behind) idle=89b/2/0 \}庢
[   72.050003]  (detected by 2, t=6003 jiffies)
[   72.050003] INFO: Stall ended before state dump start