Re: [PATCH/RFC] signal: Export signal_wake_up_state() to modules

From: Oleg Nesterov
Date: Sat May 06 2017 - 15:43:08 EST

On 05/05, Geert Uytterhoeven wrote:
> I'm using signal_wake_up() to abort a task blocked on
> wait_for_completion_interruptible(), cfr. sh_msiof_slave_abort() in
> "spi: sh-msiof: Add slave mode support"
> (
> Is exporting signal_wake_up_state() an acceptable solution?
> Alternatively, I can extract the code to abort an completion into a
> generic abort_completion() function, and export that.

I too do not think this is a good idea... signal_wake_up() or even
set_tsk_thread_flag() should never be used unless you actually send a
signal. Yes, freeze_task() does this too but note that recalc_sigpending()
checks freezing() and in this case we really want the target to enter the
get_signal() path.

And in fact I do not really understand why do you need it, it seems that
you can easily rework this code and avoid this hack.

Not to mention that sh_msiof_slave_abort() plays with struct completion
internals, this doesn't look good too.

Finally, clear_thread_flag(TIF_SIGPENDING) in sh_msiof_wait_for_completion()
looks wrong. Or it is only for kthreads?