Re: [PATCH] Use ERESTARTNOHAND if poll() is interrupted by a signal

[Manfred Spraul <manfred@colorfullife.com>]

Andrew Morton wrote:
> On Sun, 29 Jul 2007 19:05:05 +0200
> Manfred Spraul <manfred@colorfullife.com> wrote:
>
>   
>> Hi Andrew,
>>
>> poll() returns -EINTR if a signal is pending.
>> EINTR is a bad choice: it means that poll returns to user space if the
>> task is stopped by SIGSTOP/SIGCONT or by the freezer.
>> select() and ppoll() both use ERESTARTNOHAND, this avoids a return to
>> user space for signals that are handled by the kernel.
>>
>> The patch switches poll() to ERESTARTNOHAND.
>> Tested with FC6. Patch against 2.6.23-rc1-mm1.
>>     
>
> hm.  Is this a fix against
> ftp://ftp.kernel.org/pub/linux/kernel/people/akpm/patches/2.6/2.6.23-rc1/2.6.23-rc1-mm1/broken-out/do_poll-return-eintr-when-signalled.patch
> only, or does mainline also need fixing?
>
>   
Mainline has the same problem: poll() returns to user space if it's 
interrupted by SIGSTOP/SIGCONT.
> I guess the consequences of the thing-which-this-fixes aren't huge, s I ca
> queue this up for 2.6.24, after Oleg's
> do_poll-return-eintr-when-signalled.patch?
>
>   
Yes, please queue it: most/all linux versions show this behavior. 
Additionally, poll() is usually called in a loop and a spurious wakeup 
has no consequences.

--
    Manfred