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Date:   Wed, 6 Nov 2019 15:44:46 +0100
From:   Christoph Hellwig <hch@lst.de>
To:     "Darrick J. Wong" <darrick.wong@oracle.com>
Cc:     Christoph Hellwig <hch@infradead.org>, linux-xfs@vger.kernel.org,
        hch@lst.de
Subject: Re: [PATCH 2/2] xfs: periodically yield scrub threads to the
 scheduler
Message-ID: <20191106144446.GB17196@lst.de>
References: <157301537390.678524.16085197974806955970.stgit@magnolia> <157301538629.678524.5328247190031479757.stgit@magnolia>
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On Tue, Nov 05, 2019 at 08:43:06PM -0800, Darrick J. Wong wrote:
> +++ b/fs/xfs/scrub/common.h
> @@ -14,8 +14,20 @@
>  static inline bool
>  xchk_should_terminate(
>  	struct xfs_scrub	*sc,
> -	int				*error)
> +	int			*error)
>  {
> +#if !IS_ENABLED(CONFIG_PREEMPT)
> +	/*
> +	 * If preemption is disabled, we need to yield to the scheduler every
> +	 * few seconds so that we don't run afoul of the soft lockup watchdog
> +	 * or RCU stall detector.
> +	 */
> +	if (sc->next_yield != 0 && time_after(jiffies, sc->next_yield))
> +		return false;
> +	schedule();
> +	sc->next_yield = jiffies + msecs_to_jiffies(5000);
> +#endif

This looks weird.  Can't we just do a cond_resched() here?