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Date: Wed, 3 Jun 2009 00:09:39 -0700 (PDT) From: Roland McGrath <roland@...hat.com> To: Oleg Nesterov <oleg@...hat.com> Cc: Alan Cox <alan@...rguk.ukuu.org.uk>, paul@...-scientist.net, linux-kernel@...r.kernel.org, stable@...nel.org, Andrew Morton <akpm@...ux-foundation.org>, Andi Kleen <andi@...stfloor.org> Subject: Re: [PATCH] coredump: Retry writes where appropriate > Oh, I forgot about freezer... We all would like to. > Well, not good to complicate recalc_sigpending_tsk() for this unlikely case. > And this can't help, freezer does signal_wake_up() unconditionally. > > So in fact this is another argument to check signal_pending() and clear it > in dump_write/seek. I can't agree with this at all. IMHO it's far better to have a consistent definition of when TIF_SIGPENDING ought to be triggered, and have recalc_sigpending_tsk() use logic that matches the logic controlling when to set TIF_SIGPENDING asynchronously (i.e. signal_wake_up calls). > But since the coredumping task is not freezable anyway, perhaps we should > change fake_signal_wake_up() to ignore SIGNAL_GROUP_DUMPING task. That could be a long delay and a lot of i/o before suspending. > Or we should make the coredumping freezable. This means dump_write/seek > and exit_mm() should do try_to_freeze(). Yes, I think this is the thing to do for that issue. (It's kind of a separate problem.) > In any case, the coredumping is special. If ->write() returns -ERESTART/EINTR > it assumes the return to ths user-space, this is not true for the coredump. > This means that handling the spurious signals in coredump_file_write() is > not so bad if we can't avoid this. I am not so confident. It seems far too easy to wind up with some other way that TIF_SIGPENDING gets continually set and this loops, for example. (This could be some day in the future when fs, driver or pipe-io code changes somehow completely obscure.) It's far better to have confidence just in the signals code itself: the only things that set TIF_SIGPENDING interlock with the logic of the only things that are expected to clear it. Thanks, Roland -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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