The patch titled
fix-send_sigqueue-vs-thread-exit-race fix
has been added to the -mm tree. Its filename is
fix-send_sigqueue-vs-thread-exit-race-fix.patch
Patches currently in -mm which might be from [EMAIL PROTECTED] are
fix-send_sigqueue-vs-thread-exit-race.patch
fix-send_sigqueue-vs-thread-exit-race-fix.patch
ppc-c99-initializers-for-hw_interrupt_type-structures.patch
sh-c99-initializers-for-hw_interrupt_type-structures.patch
v850-c99-initializers-for-hw_interrupt_type-structures.patch
sh64-c99-initializers-for-hw_interrupt_type-structures.patch
From: Thomas Gleixner <[EMAIL PROTECTED]>
The patch below on top of your patch should solve this. We don't need
tasklist_lock to check p->flags. As you pointed out p cannot be invalid in
send_sigqueue as it's protected by get_task_struct() in create_timer()
For send_group_sigqueue it's protected by exit_itimers() waiting for
k_itimer.it_lock.
It still does not solve the ugly dependency on tasklist_lock but at least the
race and the deadlock are fixed.
Signed-off-by: Thomas Gleixner <[EMAIL PROTECTED]>
Cc: Oleg Nesterov <[EMAIL PROTECTED]>
Signed-off-by: Andrew Morton <[EMAIL PROTECTED]>
---
kernel/posix-timers.c | 3 ++-
kernel/signal.c | 25 ++++++++++++++++++++++---
2 files changed, 24 insertions(+), 4 deletions(-)
diff -puN kernel/posix-timers.c~fix-send_sigqueue-vs-thread-exit-race-fix
kernel/posix-timers.c
--- devel/kernel/posix-timers.c~fix-send_sigqueue-vs-thread-exit-race-fix
2005-08-21 22:31:05.000000000 -0700
+++ devel-akpm/kernel/posix-timers.c 2005-08-21 22:31:05.000000000 -0700
@@ -501,7 +501,8 @@ static void posix_timer_fn(unsigned long
remove_from_abslist(timr);
}
- if (posix_timer_event(timr, si_private))
+ /* Do not rearm the timer, when we are exiting */
+ if (posix_timer_event(timr, si_private) > 0)
/*
* signal was not sent because of sig_ignor
* we will not get a call back to restart it AND
diff -puN kernel/signal.c~fix-send_sigqueue-vs-thread-exit-race-fix
kernel/signal.c
--- devel/kernel/signal.c~fix-send_sigqueue-vs-thread-exit-race-fix
2005-08-21 22:31:05.000000000 -0700
+++ devel-akpm/kernel/signal.c 2005-08-21 22:31:05.000000000 -0700
@@ -1367,8 +1367,15 @@ send_sigqueue(int sig, struct sigqueue *
int ret = 0;
BUG_ON(!(q->flags & SIGQUEUE_PREALLOC));
- read_lock(&tasklist_lock);
+retry:
+ if (unlikely(p->flags & PF_EXITING))
+ return -1;
+
+ if (unlikely(!read_trylock(&tasklist_lock))) {
+ cpu_relax();
+ goto retry;
+ }
if (unlikely(p->flags & PF_EXITING)) {
ret = -1;
goto out_err;
@@ -1413,7 +1420,18 @@ send_group_sigqueue(int sig, struct sigq
int ret = 0;
BUG_ON(!(q->flags & SIGQUEUE_PREALLOC));
- read_lock(&tasklist_lock);
+retry:
+ if (unlikely(p->flags & PF_EXITING))
+ return -1;
+
+ if (unlikely(!read_trylock(&tasklist_lock))) {
+ cpu_relax();
+ goto retry;
+ }
+ if (unlikely(p->flags & PF_EXITING)) {
+ ret = -1;
+ goto out_err;
+ }
spin_lock_irqsave(&p->sighand->siglock, flags);
handle_stop_signal(sig, p);
@@ -1447,8 +1465,9 @@ send_group_sigqueue(int sig, struct sigq
__group_complete_signal(sig, p);
out:
spin_unlock_irqrestore(&p->sighand->siglock, flags);
+out_err:
read_unlock(&tasklist_lock);
- return(ret);
+ return ret;
}
/*
_
-
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