Messages in this thread Patch in this message | | | Date | Mon, 20 Feb 2006 19:03:13 +0300 | From | Oleg Nesterov <> | Subject | [PATCH 1/2] copy_process: cleanup bad_fork_cleanup_sighand |
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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: - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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