[PATCH] copy_process: cleanup bad_fork_cleanup_sighand
The only caller of exit_sighand(tsk) is copy_process's error path. We can
call __exit_sighand() directly and kill exit_sighand().
This 'tsk' was not yet registered in pid_hash[] or init_task.tasks, it has no
external references, nobody can see it, and
IF (clone_flags & CLONE_SIGHAND)
At least 'current' has a reference to ->sighand, this
means atomic_dec_and_test(sighand->count) can't be true.
ELSE
Nobody can see this ->sighand, this means we can free it
without any locking.
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Acked-by: "Paul E. McKenney" <paulmck@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/include/linux/sched.h b/include/linux/sched.h
index ca1fd31..69c2a1e 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1151,7 +1151,6 @@
extern void exit_files(struct task_struct *);
extern void exit_signal(struct task_struct *);
extern void __exit_signal(struct task_struct *);
-extern void exit_sighand(struct task_struct *);
extern void __exit_sighand(struct task_struct *);
extern void exit_itimers(struct signal_struct *);
diff --git a/kernel/fork.c b/kernel/fork.c
index 33ffb5b..8a46ad5 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1208,7 +1208,8 @@
bad_fork_cleanup_signal:
exit_signal(p);
bad_fork_cleanup_sighand:
- exit_sighand(p);
+ if (p->sighand)
+ __exit_sighand(p);
bad_fork_cleanup_fs:
exit_fs(p); /* blocking */
bad_fork_cleanup_files:
diff --git a/kernel/signal.c b/kernel/signal.c
index c5b65aa..1d7f446 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -336,20 +336,6 @@
kmem_cache_free(sighand_cachep, sighand);
}
-void exit_sighand(struct task_struct *tsk)
-{
- write_lock_irq(&tasklist_lock);
- rcu_read_lock();
- if (tsk->sighand != NULL) {
- struct sighand_struct *sighand = rcu_dereference(tsk->sighand);
- spin_lock(&sighand->siglock);
- __exit_sighand(tsk);
- spin_unlock(&sighand->siglock);
- }
- rcu_read_unlock();
- write_unlock_irq(&tasklist_lock);
-}
-
/*
* This function expects the tasklist_lock write-locked.
*/