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Commit 7001510d authored by Oleg Nesterov's avatar Oleg Nesterov Committed by Linus Torvalds
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[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: default avatarOleg Nesterov <oleg@tv-sign.ru>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Acked-by: default avatar"Paul E. McKenney" <paulmck@us.ibm.com>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent a9e88e84

include/linux/sched.h

+0 −1
Original line number Original line Diff line number Diff line
@@ -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 *);

kernel/fork.c

+2 −1
Original line number Original line Diff line number Diff line
@@ -1208,7 +1208,8 @@ static task_t *copy_process(unsigned long clone_flags, 
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:

kernel/signal.c

+0 −14
Original line number Original line Diff line number Diff line
@@ -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.

 */

 */