From: Oleg Nesterov <oleg@tv-sign.ru>
To: Andrew Morton <akpm@osdl.org>
Cc: linux-kernel@vger.kernel.org, Ingo Molnar <mingo@elte.hu>,
"Paul E. McKenney" <paulmck@us.ibm.com>,
"Eric W. Biederman" <ebiederm@xmission.com>,
Roland McGrath <roland@redhat.com>
Subject: [PATCH 1/2] copy_process: cleanup bad_fork_cleanup_sighand
Date: Mon, 20 Feb 2006 19:03:13 +0300 [thread overview]
Message-ID: <43F9E841.FD560455@tv-sign.ru> (raw)
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>
--- 2.6.16-rc3/include/linux/sched.h~1_SIGH 2006-02-18 22:13:44.000000000 +0300
+++ 2.6.16-rc3/include/linux/sched.h 2006-02-20 00:38:57.000000000 +0300
@@ -1143,7 +1143,6 @@ extern void exit_thread(void);
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 *);
--- 2.6.16-rc3/kernel/signal.c~1_SIGH 2006-02-19 21:08:23.000000000 +0300
+++ 2.6.16-rc3/kernel/signal.c 2006-02-20 00:37:34.000000000 +0300
@@ -336,20 +336,6 @@ void __exit_sighand(struct task_struct *
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.
*/
--- 2.6.16-rc3/kernel/fork.c~1_SIGH 2006-02-18 01:11:59.000000000 +0300
+++ 2.6.16-rc3/kernel/fork.c 2006-02-20 00:38:39.000000000 +0300
@@ -1196,7 +1196,8 @@ bad_fork_cleanup_mm:
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:
next reply other threads:[~2006-02-20 14:46 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-02-20 16:03 Oleg Nesterov [this message]
2006-02-20 16:07 ` [PATCH 1/2] copy_process: cleanup bad_fork_cleanup_sighand Oleg Nesterov
2006-02-24 17:35 ` Paul E. McKenney
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