linux-kernel - Re: [RFC][PATCH 4/7] inotify: Deal with nested sleeps

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Date:	Tue, 5 Aug 2014 09:28:13 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Lai Jiangshan <laijs@...fujitsu.com>
Cc:	mingo@...nel.org, oleg@...hat.com, torvalds@...ux-foundation.org,
	tglx@...utronix.de, ilya.dryomov@...tank.com,
	umgwanakikbuti@...il.com, linux-kernel@...r.kernel.org,
	Eric Paris <eparis@...isplace.org>,
	John McCutchan <john@...nmccutchan.com>,
	Robert Love <rlove@...ve.org>
Subject: Re: [RFC][PATCH 4/7] inotify: Deal with nested sleeps

On Tue, Aug 05, 2014 at 10:22:11AM +0800, Lai Jiangshan wrote:
> I don't think this one needs nested sleeps.
> 
> diff --git a/fs/notify/inotify/inotify_user.c b/fs/notify/inotify/inotify_user.c
> index cc423a3..1ca5888 100644
> --- a/fs/notify/inotify/inotify_user.c
> +++ b/fs/notify/inotify/inotify_user.c
> @@ -233,15 +233,16 @@ static ssize_t inotify_read(struct file *file, char __user *buf,
>  	group = file->private_data;
>  
>  	while (1) {
> +		mutex_lock(&group->notification_mutex);
>  		prepare_to_wait(&group->notification_waitq, &wait, TASK_INTERRUPTIBLE);
>  
> -		mutex_lock(&group->notification_mutex);
>  		kevent = get_one_event(group, count);
>  		mutex_unlock(&group->notification_mutex);
>  
>  		pr_debug("%s: group=%p kevent=%p\n", __func__, group, kevent);
>  
>  		if (kevent) {
> +			__set_current_state(TASK_RUNNING);
>  			ret = PTR_ERR(kevent);
>  			if (IS_ERR(kevent))
>  				break;

Yeah, that'll probably work, but I'm not sure this the place to be
creative like that though. But whatever the inotify people prefer
really.
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