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[PATCH] 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>
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>
This commit is contained in:
Oleg Nesterov 2006-03-28 16:11:14 -08:00 • committed by Linus Torvalds
parent a9e88e84b5
commit 7001510d0c
3 changed files with 2 additions and 16 deletions
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1
include/linux/sched.h
View file

@ -1151,7 +1151,6 @@ extern void exit_thread(void);
extern void exit_files(struct task_struct *); extern void exit_files(struct task_struct *);
extern void exit_signal(struct task_struct *); extern void exit_signal(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_sighand(struct task_struct *);
extern void exit_itimers(struct signal_struct *); extern void exit_itimers(struct signal_struct *);

3
kernel/fork.c
View file

@ -1208,7 +1208,8 @@ bad_fork_cleanup_mm:
bad_fork_cleanup_signal: bad_fork_cleanup_signal:
exit_signal(p); exit_signal(p);
bad_fork_cleanup_sighand: bad_fork_cleanup_sighand:
exit_sighand(p); if (p->sighand)
__exit_sighand(p);
bad_fork_cleanup_fs: bad_fork_cleanup_fs:
exit_fs(p); /* blocking */ exit_fs(p); /* blocking */
bad_fork_cleanup_files: bad_fork_cleanup_files:

14
kernel/signal.c
View file

@ -336,20 +336,6 @@ void __exit_sighand(struct task_struct *tsk)
kmem_cache_free(sighand_cachep, sighand); 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. * This function expects the tasklist_lock write-locked.
*/ */