The patch titled
sched: fix TASK_WAKEKILL vs SIGKILL race
has been removed from the -mm tree. Its filename was
sched-fix-task_wakekill-vs-sigkill-race.patch
This patch was dropped because it was merged into mainline or a subsystem tree
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
linux-next.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
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