Re: PATCH: sleeping while holding a lock in _pagebuf_free_bh()::page_buf.c

[Andi Kleen <ak@xxxxxxx>]

> >From what I can see and read, wake_up() and wake_up_sync() both wake
> up all non-exclusive sleepers and one exclusive sleeper.
> 
> The NON _sync versions, OTOH, will call reschedule_idle(), which _may_
> cause (if the conditions are favourable) _another_ task to run
> on _another_ CPU (SMP), _before_ the wake_up() returns.

Yes of course. But other CPUs are completely independent anyways, so 
there can be tasks scheduled there any time, no matter if you call
wake_up or not.

> This will cause a problem if that other task does IO on xfs
> and the code is as it was several days ago.

Can you explain how exactly that leads to problems ?

-Andi