linux-kernel - Re: [PATCH AUTOSEL 5.5 542/542] pipe: use exclusive waits when reading or writing

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Message-ID: <20200218182041.GB24185@bombadil.infradead.org>
Date:   Tue, 18 Feb 2020 10:20:41 -0800
From:   Matthew Wilcox <willy@...radead.org>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     Andrei Vagin <avagin@...il.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Sasha Levin <sashal@...nel.org>,
        stable <stable@...r.kernel.org>,
        Josh Triplett <josh@...htriplett.org>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>
Subject: Re: [PATCH AUTOSEL 5.5 542/542] pipe: use exclusive waits when
 reading or writing

On Tue, Feb 18, 2020 at 10:17:30AM -0800, Linus Torvalds wrote:
> @@ -722,9 +722,10 @@ pipe_release(struct inode *inode, struct file *file)
>  	if (file->f_mode & FMODE_WRITE)
>  		pipe->writers--;
>  
> -	if (pipe->readers || pipe->writers) {
> -		wake_up_interruptible_sync_poll(&pipe->rd_wait, EPOLLIN | EPOLLRDNORM | EPOLLERR | EPOLLHUP);
> -		wake_up_interruptible_sync_poll(&pipe->wr_wait, EPOLLOUT | EPOLLWRNORM | EPOLLERR | EPOLLHUP);
> +	/* Was that the last reader or writer, but not the other side? */
> +	if (!pipe->readers != !pipe->writers) {
> +		wake_up_interruptible_all(&pipe->rd_wait);
> +		wake_up_interruptible_all(&pipe->wr_wait);
>  		kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
>  		kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
>  	}
> @@ -1026,8 +1027,8 @@ static int wait_for_partner(struct pipe_inode_info *pipe, unsigned int *cnt)
>  
>  static void wake_up_partner(struct pipe_inode_info *pipe)
>  {
> -	wake_up_interruptible(&pipe->rd_wait);
> -	wake_up_interruptible(&pipe->wr_wait);
> +	wake_up_interruptible_all(&pipe->rd_wait);
> +	wake_up_interruptible_all(&pipe->wr_wait);
>  }

You don't want to move wake_up_partner() up and call it from pipe_release()?