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SubjectRe: heavy handed exit() in latest BK

On Sat, 8 Feb 2003, Linus Torvalds wrote:
>
> And then the call trace would be very interesting indeed if the above bug
> triggers.. (and unlike the do_exit() bug, the tri_to_wake_up() thing
> should clearly pinpoint where the problem actually happens, knock wood).

Ok, let's assume it was the wake_up_process() in handle_stop_signal(),
then hopefully this (totally untested) patch should fix it.

Roland, does this look sane to you? It makes the STOP wakeup be a
SIGCONT-only thing, and makes the wakeup conditional on !PF_EXITING.

It also makes SIGKILL ignore the stopped status for delivery.

Does this make the gdb test-suite happy?

Linus

---
===== kernel/signal.c 1.61 vs edited =====
--- 1.61/kernel/signal.c Fri Feb 7 06:46:13 2003
+++ edited/kernel/signal.c Sat Feb 8 18:29:11 2003
@@ -591,8 +591,7 @@
rm_from_queue(sigmask(SIGCONT), &t->pending);
t = next_thread(t);
} while (t != p);
- }
- else if (sig_kernel_cont(sig)) {
+ } else if (sig == SIGCONT) {
/*
* Remove all stop signals from all queues,
* and wake all threads.
@@ -637,17 +636,12 @@
* running the handler. With the TIF_SIGPENDING
* flag set, the thread will pause and acquire the
* siglock that we hold now and until we've queued
- * the pending signal. For SIGKILL, we likewise
- * don't want anybody doing anything but taking the
- * SIGKILL. The only case in which a thread would
- * not already be in the signal dequeuing loop is
- * non-signal (e.g. syscall) ptrace tracing, so we
- * don't worry about an unnecessary trip through
- * the signal code and just keep this code path
- * simpler by unconditionally setting the flag.
+ * the pending signal.
*/
- set_tsk_thread_flag(t, TIF_SIGPENDING);
- wake_up_process(t);
+ if (!(t->flags & PF_EXITING)) {
+ set_tsk_thread_flag(t, TIF_SIGPENDING);
+ wake_up_process(t);
+ }
t = next_thread(t);
} while (t != p);
}
@@ -789,15 +783,17 @@
* as soon as they're available, so putting the signal on the shared queue
* will be equivalent to sending it to one such thread.
*/
-#define wants_signal(sig, p) (!sigismember(&(p)->blocked, sig) \
- && (p)->state < TASK_STOPPED \
- && !((p)->flags & PF_EXITING) \
- && (task_curr(p) || !signal_pending(p)))
+#define wants_signal(sig, p, mask) \
+ (!sigismember(&(p)->blocked, sig) \
+ && ((p)->state & mask) \
+ && !((p)->flags & PF_EXITING) \
+ && (task_curr(p) || !signal_pending(p)))

static inline int
__group_send_sig_info(int sig, struct siginfo *info, struct task_struct *p)
{
struct task_struct *t;
+ unsigned int mask;
int ret;

#if CONFIG_SMP
@@ -815,6 +811,14 @@
return 0;

/*
+ * Normally we only post signals to non-stopped threads,
+ * bit SIGKILL will puch through that too..
+ */
+ mask = TASK_RUNNING | TASK_INTERRUPTIBLE | TASK_UNINTERRUPTIBLE;
+ if (sig == SIGKILL)
+ mask |= TASK_STOPPED;
+
+ /*
* Put this signal on the shared-pending queue, or fail with EAGAIN.
* We always use the shared queue for process-wide signals,
* to avoid several races.
@@ -829,7 +833,7 @@
* If the main thread wants the signal, it gets first crack.
* Probably the least surprising to the average bear.
*/
- if (wants_signal(sig, p))
+ if (wants_signal(sig, p, mask))
t = p;
else if (thread_group_empty(p))
/*
@@ -847,7 +851,7 @@
t = p->signal->curr_target = p;
BUG_ON(t->tgid != p->tgid);

- while (!wants_signal(sig, t)) {
+ while (!wants_signal(sig, t, mask)) {
t = next_thread(t);
if (t == p->signal->curr_target)
/*
-
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