The patch titled sched: fix TASK_WAKEKILL vs SIGKILL race has been added to the -mm tree. Its filename is sched-fix-task_wakekill-vs-sigkill-race.patch Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/SubmitChecklist when testing your code *** See http://www.zip.com.au/~akpm/linux/patches/stuff/added-to-mm.txt to find out what to do about this The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/ ------------------------------------------------------ Subject: sched: fix TASK_WAKEKILL vs SIGKILL race From: Oleg Nesterov <oleg@xxxxxxxxxx> schedule() has the special "TASK_INTERRUPTIBLE && signal_pending()" case, this allows us to do current->state = TASK_INTERRUPTIBLE; schedule(); without fear to sleep with pending signal. However, the code like current->state = TASK_KILLABLE; schedule(); is not right, schedule() doesn't take TASK_WAKEKILL into account. This means that mutex_lock_killable(), wait_for_completion_killable(), down_killable(), schedule_timeout_killable() can miss SIGKILL (and btw the second SIGKILL has no effect). Introduce the new helper, signal_pending_state(), and change schedule() to use it. Hopefully it will have more users, that is why the task's state is passed separately. Note this "__TASK_STOPPED | __TASK_TRACED" check in signal_pending_state(). This is needed to preserve the current behaviour (ptrace_notify). I hope this check will be removed soon, but this (afaics good) change needs the separate discussion. The fast path is "(state & (INTERRUPTIBLE | WAKEKILL)) + signal_pending(p)", basically the same that schedule() does now. However, this patch of course bloats schedule(). Signed-off-by: Oleg Nesterov <oleg@xxxxxxxxxx> Cc: Ingo Molnar <mingo@xxxxxxx> Cc: Matthew Wilcox <matthew@xxxxxx> Cc: Dmitry Adamushko <dmitry.adamushko@xxxxxxxxx> Cc: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx> Cc: Roland McGrath <roland@xxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- include/linux/sched.h | 13 +++++++++++++ kernel/sched.c | 6 ++---- 2 files changed, 15 insertions(+), 4 deletions(-) diff -puN include/linux/sched.h~sched-fix-task_wakekill-vs-sigkill-race include/linux/sched.h --- a/include/linux/sched.h~sched-fix-task_wakekill-vs-sigkill-race +++ a/include/linux/sched.h @@ -2040,6 +2040,19 @@ static inline int fatal_signal_pending(s return signal_pending(p) && __fatal_signal_pending(p); } +static inline int signal_pending_state(long state, struct task_struct *p) +{ + if (!(state & (TASK_INTERRUPTIBLE | TASK_WAKEKILL))) + return 0; + if (!signal_pending(p)) + return 0; + + if (state & (__TASK_STOPPED | __TASK_TRACED)) + return 0; + + return (state & TASK_INTERRUPTIBLE) || __fatal_signal_pending(p); +} + static inline int need_resched(void) { return unlikely(test_thread_flag(TIF_NEED_RESCHED)); diff -puN kernel/sched.c~sched-fix-task_wakekill-vs-sigkill-race kernel/sched.c --- a/kernel/sched.c~sched-fix-task_wakekill-vs-sigkill-race +++ a/kernel/sched.c @@ -4207,12 +4207,10 @@ need_resched_nonpreemptible: clear_tsk_need_resched(prev); if (prev->state && !(preempt_count() & PREEMPT_ACTIVE)) { - if (unlikely((prev->state & TASK_INTERRUPTIBLE) && - signal_pending(prev))) { + if (unlikely(signal_pending_state(prev->state, prev))) prev->state = TASK_RUNNING; - } else { + else deactivate_task(rq, prev, 1); - } switch_count = &prev->nvcsw; } _ Patches currently in -mm which might be from oleg@xxxxxxxxxx are origin.patch sched-fix-task_wakekill-vs-sigkill-race.patch __mutex_lock_common-use-signal_pending_state.patch do_generic_file_read-s-eintr-eio-if-lock_page_killable-fails.patch introduce-pf_kthread-flag.patch kill-pf_borrowed_mm-in-favour-of-pf_kthread.patch coredump-zap_threads-must-skip-kernel-threads.patch posix-timers-timer_delete-remove-the-bogus-it_process-=-null-check.patch posix-timers-release_posix_timer-kill-the-bogus-put_task_struct-it_process.patch signals-collect_signal-remove-the-unneeded-sigismember-check.patch signals-collect_signal-simplify-the-still_pending-logic.patch signals-change-collect_signal-to-return-void.patch __exit_signal-dont-take-rcu-lock.patch signals-dequeue_signal-dont-check-signal_group_exit-when-setting-signal_stop_dequeued.patch signals-do_signal_stop-kill-the-signal_unkillable-check.patch coredump-zap_threads-comments-use-while_each_thread.patch distinct-tgid-tid-i-o-statistics.patch -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html