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author | Oleg Nesterov <oleg@tv-sign.ru> | 2008-06-08 17:20:41 (GMT) |
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committer | Ingo Molnar <mingo@elte.hu> | 2008-06-10 09:37:25 (GMT) |
commit | 16882c1e962b4be5122fc05aaf2afc10fd9e2d15 (patch) | |
tree | c39cae4ae4874998d7e3486cd57d57613b05a89c /include/linux/sched.h | |
parent | 39b945a37bac2b692773a470890c8ba301485b15 (diff) | |
download | linux-fsl-qoriq-16882c1e962b4be5122fc05aaf2afc10fd9e2d15.tar.xz |
sched: fix TASK_WAKEKILL vs SIGKILL race
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@tv-sign.ru>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'include/linux/sched.h')
-rw-r--r-- | include/linux/sched.h | 13 |
1 files changed, 13 insertions, 0 deletions
diff --git a/include/linux/sched.h b/include/linux/sched.h index ae0be3c..c5d3f84 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -2026,6 +2026,19 @@ static inline int fatal_signal_pending(struct task_struct *p) 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)); |