Re: [patch -rt] Fix infinite loop with 2.6.31.4-rt14 V2

[Darren Hart]

Darren Hart wrote:
> Dinakar Guniguntala wrote:
>  > Application threads calling futex_wait_requeue_pi run in an infinite 
> loop
>  > in the kernel if the futex value changes during the call. The following
>  > patch fixes the problem.
>
> The key bit here being that EAGAIN == EWOULDBLOCK - who thought that was 
> a good idea?

And now that I think about it, when I reviewed this original patch I
remember mentioning that this isn't even needed for
futex_wait_requeue_pi() because we don't have the same wake-up race as
futex_wait() suffers from - since we don't use the same lock_ptr == NULL
test (nor do we use the wake_list in the requeue code). I suspect the
only case where -EAGAIN is being used here is when the uval doesn't
match val - no spurious wakeups.

Dino, can you try with the following patch which just reverts the
spurious wakeup handling for the requeue_pi path.