From: Manfred Spraul <manfred@colorfullife.com>
de_thread is called by exec to kill all threads in the thread group except
the threads required for exec.
The waiting is implemented by waiting for a wakeup from __exit_signal: If
the reference count is less or equal to 2, then the waiter is woken up. If
exec is called by a non-leader thread, then two threads are required for
exec.
But if a thread group leader calls exec, then only one thread is required
for exec. Thus the hardcoded "2" leads to a superfluous wakeup. The patch
fixes that by adding a "notify_count" field to the signal structure.
fs/exec.c | 1 +
include/linux/sched.h | 6 ++++++
kernel/signal.c | 2 +-
3 files changed, 8 insertions(+), 1 deletion(-)
diff -puN fs/exec.c~notify_count-for-de_thread fs/exec.c
--- 25/fs/exec.c~notify_count-for-de_thread 2003-05-18 11:18:57.000000000 -0700
+++ 25-akpm/fs/exec.c 2003-05-18 11:18:57.000000000 -0700
@@ -609,6 +609,7 @@ static inline int de_thread(struct task_
count = 1;
while (atomic_read(&oldsig->count) > count) {
oldsig->group_exit_task = current;
+ oldsig->notify_count = count;
__set_current_state(TASK_UNINTERRUPTIBLE);
spin_unlock_irq(lock);
schedule();
diff -puN include/linux/sched.h~notify_count-for-de_thread include/linux/sched.h
--- 25/include/linux/sched.h~notify_count-for-de_thread 2003-05-18 11:18:57.000000000 -0700
+++ 25-akpm/include/linux/sched.h 2003-05-18 11:18:57.000000000 -0700
@@ -264,7 +264,13 @@ struct signal_struct {
/* thread group exit support */
int group_exit;
int group_exit_code;
+ /* overloaded:
+ * - notify group_exit_task when ->count is equal to notify_count
+ * - everyone except group_exit_task is stopped during signal delivery
+ * of fatal signals, group_exit_task processes the signal.
+ */
struct task_struct *group_exit_task;
+ int notify_count;
/* thread group stop support, overloads group_exit_code too */
int group_stop_count;
diff -puN kernel/signal.c~notify_count-for-de_thread kernel/signal.c
--- 25/kernel/signal.c~notify_count-for-de_thread 2003-05-18 11:18:57.000000000 -0700
+++ 25-akpm/kernel/signal.c 2003-05-18 11:18:57.000000000 -0700
@@ -336,7 +336,7 @@ void __exit_signal(struct task_struct *t
* If there is any task waiting for the group exit
* then notify it:
*/
- if (sig->group_exit_task && atomic_read(&sig->count) <= 2) {
+ if (sig->group_exit_task && atomic_read(&sig->count) == sig->notify_count) {
wake_up_process(sig->group_exit_task);
sig->group_exit_task = NULL;
}
_