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SubjectRe: [Patch] fix the lockdep warning in tty_fasync()
Date
> Commit 703625118 causes a lockdep warning:
>
> [ INFO: possible irq lock inversion dependency detected ]
> 2.6.33-rc5 #77
> ---------------------------------------------------------
> emacs/1609 just changed the state of lock:
> (&(&tty->ctrl_lock)->rlock){+.....}, at: [<ffffffff8127c648>]
> tty_fasync+0xe8/0x190
> but this lock took another, HARDIRQ-unsafe lock in the past:
> (&(&sighand->siglock)->rlock){-.....}
>
> This is due to we use write_lock_irq() in __f_setown() which turns
> the IRQ on in write_unlock_irq(), causes this warning.
>
> Switch it to write_lock_irqsave() and write_unlock_irqrestore(),
> as suggested by Eric.
>
> Reported-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
> Signed-off-by: WANG Cong <xiyou.wangcong@gmail.com>
> Cc: "Eric W. Biederman" <ebiederm@xmission.com>
>
> ---
> diff --git a/fs/fcntl.c b/fs/fcntl.c
> index 97e01dc..82cc8a7 100644
> --- a/fs/fcntl.c
> +++ b/fs/fcntl.c
> @@ -199,7 +199,8 @@ static int setfl(int fd, struct file * filp, unsigned long arg)
> static void f_modown(struct file *filp, struct pid *pid, enum pid_type type,
> int force)
> {
> - write_lock_irq(&filp->f_owner.lock);
> + unsigned long flags;
> + write_lock_irqsave(&filp->f_owner.lock, flags);
> if (force || !filp->f_owner.pid) {
> put_pid(filp->f_owner.pid);
> filp->f_owner.pid = get_pid(pid);
> @@ -211,7 +212,7 @@ static void f_modown(struct file *filp, struct pid *pid, enum pid_type type,
> filp->f_owner.euid = cred->euid;
> }
> }
> - write_unlock_irq(&filp->f_owner.lock);
> + write_unlock_irqrestore(&filp->f_owner.lock, flags);
> }
>
> int __f_setown(struct file *filp, struct pid *pid, enum pid_type type,

I've confirmed the warning disappear :)

Thanks.




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