Re: [rfc][patch] futex: restartable futex_wait?

[Ingo Molnar <mingo@elte.hu>]

* Nick Piggin <npiggin@suse.de> wrote:

> Hi Ingo,
> 
> I'm seeing an LTP test fail for ltp test sigaction_16_24. Basically, 
> it tests whether the SA_RESTART flag works for the sem_wait operation.
> 
> I see sem_wait is implemented with futex_wait, so I wonder whether we 
> can make it restartable? Am I going about it the right way? (Seems to 
> fix the testcase here).

i think that's quite right. I'm wondering why this never came up before? 
But your fix is not complete i think:

> +             restart->arg2 = time;
> +             return -ERESTART_RESTARTBLOCK;
> +     }

'time' here is relative, so the restarted syscall will do a /full/ wait 
again.

maybe we should rather convert futex timed-waits to hrtimers? Thomas?

	Ingo