Re: futex(2) man page update help request

On Sat, 2015-01-24 at 12:35 +0100, Thomas Gleixner wrote:

So we should never see -EINTR in the case of a spurious wakeup here.

But, here is the not so good news:

 I did some archaeology. The restart handling of futex_wait() got
 introduced in kernel 2.6.22, so anything older than that will have
 the spurious -EINTR issues.

futex_wait_pi() always had the restart handling and glibc folks back
then (2006) requested that it should never return -EINTR, so it
unconditionally restarts the syscall whether a signal had been
delivered or not.

So kernels >= 2.6.22 should never return -EINTR spuriously. If that
happens it's a bug and needs to be fixed.

Thanks for looking into this.

Michael, can you include the above in the documentation please?  This is
useful for userspace code like glibc that expects a minimum kernel
version.  Thanks!

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