Sorry for being late, I've just realized that you are discussing the freezer here. ;-)
On Wednesday, 13 June 2007 17:15, Oleg Nesterov wrote: > Sorry for delay, I was completely offline, > > On 06/06, Roland McGrath wrote: > > > > [PATCH] Restrict clearing TIF_SIGPENDING > > > > This patch should get a few birds. It prevents sigaction calls from > > clearing TIF_SIGPENDING in other threads, which could leak -ERESTART*. > > It fixes ptrace_stop not to clear it, which done at the syscall exit > > stop could leak -ERESTART*. It probably removes the harm from > > signalfd, at least assuming it never calls dequeue_signal on kernel > > threads that might have used block_all_signals. > > > > Signed-off-by: Roland McGrath <[EMAIL PROTECTED]> > > --- > > kernel/signal.c | 40 ++++++++++++++++++++++++---------------- > > 1 files changed, 24 insertions(+), 16 deletions(-) > > > > diff --git a/kernel/signal.c b/kernel/signal.c > > index acdfc05..dc5797c 100644 > > --- a/kernel/signal.c > > +++ b/kernel/signal.c > > @@ -105,7 +105,11 @@ static int recalc_sigpending_tsk(struct > > set_tsk_thread_flag(t, TIF_SIGPENDING); > > return 1; > > } > > - clear_tsk_thread_flag(t, TIF_SIGPENDING); > > + /* > > + * We must never clear the flag in another thread, or in current > > + * when it's possible the current syscall is returning -ERESTART*. > > + * So we don't clear it here, and only callers who know they should do. > > + */ > > return 0; > > } > > This breaks cancel_freezing(). Somehow we should clear TIF_SIGPENDING for > kernel threads. Otherwise we may have subtle failures if try_to_freeze_tasks() > fails. Well, the only code path in which we'd want to call cancel_freezing() for kernel threads is when the freezing of kernel threads. However, this only happens if one of the kernel threads declares itself as freezable and the fails to call try_to_freeze(), which is a bug. Thus I don't think that we need to worry about that case too much. Moreover, I'm not sure that it's a good idea at all to send signals to kernel threads from the freezer, since in fact we only need to wake them up to make them call try_to_freeze() (after we've set TIF_FREEZE for them). Greetings, Rafael -- "Premature optimization is the root of all evil." - Donald Knuth - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
