Re: futex(2) man page update help request

[Michael Kerrisk (man-pages)]

Hello Torvald,

On 01/24/2015 02:12 PM, Torvald Riegel wrote:
> 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!

I've added some text to my draft to cover this point.

Cheers,

Michael


-- 
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
Linux/UNIX System Programming Training: http://man7.org/training/
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