Re: [RESEND v2] irq: Refactor irq_wait_for_interrupt info to simplify the code

[Thomas Gleixner <tglx@linutronix.de>]

chengkaitao <pilgrimtao@gmail.com> writes:
> From: Kaitao Cheng <pilgrimtao@gmail.com>
>
> Cleanup extra if(test_and_clear_bit), and put the other one in front.

That simplifies the code but opens a race window:

 CPU 0                                CPU 1
                                      irq_wait_for_interrupt()
                                        has not yet reached schedule()
 free_irq()
   remove_action();
   synchronize_irq();                   

   #ifdef CONFIG_DEBUG_SHIRQ
    action->handler()                   if (test_and_clear_bit())
                            ---> bit is not set yet                                           
      --> SET thread running
   #endif                               

   kthread_stop()                       if (kthread_stop())

                   ---> Leave with bit set and thread active count != 0

That's just the most obvious example...

Thanks,

        tglx