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SubjectRe: [PATCH -mm 3/3] proc: make task_sig() lockless
Date
> Yes. From the changelog:
>
> Of course, this means we read pending/blocked/etc nonatomically,
> but I hope this is OK for fs/proc.
>
> But I don't think the returned data could be "really" inconsistent
> from the /bin/ps pov. Yes, it is possible that, say, some signal is
> seen as both pending and ignored without ->siglock. Or we can report
> user->sigpending != 0 while pending/shpending are empty.
>
> But this looks harmless to me. We never guaranteed /proc/pid/status
> can't report the "intermediate" state, and I don't think we can
> confuse the user-space.
>
> Do you agree? Or do you think this can make problems ?

I'm not so sure. Operations like sigprocmask and sigaction really have
always been entirely atomic from the userland perspective before. Now it
becomes possible to read from /proc e.g. a blocked set that never existed
as such (one word updated by sigprocmask but not yet the next word).


Thanks,
Roland


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