linux-kernel - Re: [PATCH] sched: Avoid that __wait_on_bit

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Message-ID: <20160813170744.GA2868@redhat.com>
Date:	Sat, 13 Aug 2016 19:07:45 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Bart Van Assche <bart.vanassche@...disk.com>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	"mingo@...nel.org" <mingo@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Johannes Weiner <hannes@...xchg.org>,
	Neil Brown <neilb@...e.de>,
	Michael Shaver <jmshaver@...il.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] sched: Avoid that __wait_on_bit_lock() hangs

Forgot to mention...

On 08/12, Bart Van Assche wrote:
>
> --- a/mm/filemap.c
> +++ b/mm/filemap.c
> @@ -1643,7 +1643,12 @@ find_page:
>  			 * wait_on_page_locked is used to avoid unnecessarily
>  			 * serialisations and why it's safe.
>  			 */
> -			wait_on_page_locked_killable(page);
> +			error = wait_on_page_locked_killable(page);
> +			if (error == -EINTR) {
> +				put_page(page);
> +				goto out;
> +			}
> +			error = 0;

This change probably makes sense regardless although I'd suggest to
simplify it:

	-		wait_on_page_locked_killable(page);
	+		error = wait_on_page_locked_killable(page);
	+		if (unlikely(error))
	+			goto readpage_error;


but it looks off-topic. And the changelog looks misleading/wrong.

I do not think this change makes sense in this debugging session,

Oleg.