[Devel] Re: [PATCH 1/13] BC: atomic_dec_and_lock_irqsave() helper

[Kirill Korotaev]

> Hello Kirill, Hello Pavel,
> 
> Kirill Korotaev wrote:
> 
>>Oleg Nesterov noticed to me that the construction like
>>(used in beancounter patches and free_uid()):
>>
>>  local_irq_save(flags);
>>  if (atomic_dec_and_lock(&refcnt, &lock))
>>	  ...
>>
>>is not that good for preemtible kernels, since with preemption
>>spin_lock() can schedule() to reduce latency. However, it won't schedule
>>if interrupts are disabled.
>>
>>So this patch introduces atomic_dec_and_lock_irqsave() as a logical
>>counterpart to atomic_dec_and_lock().
> 
> 
> You should probably send that one independently from the BC 
> patchset. 
Maybe, but BCs are the only user of this so far...

Thanks,
Kirill