linux-kernel - Re: 4.6-rc1 regression in SPI core -- deadlock

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Date:	Mon, 4 Apr 2016 09:23:31 +0530
From:	Vignesh R <vigneshr@...com>
To:	Rich Felker <dalias@...c.org>,
	"linux-spi@...r.kernel.org" <linux-spi@...r.kernel.org>
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Jon Hunter <jonathanh@...dia.com>,
	Mark Brown <broonie@...nel.org>
Subject: Re: 4.6-rc1 regression in SPI core -- deadlock



On 04/04/2016 06:50 AM, Rich Felker wrote:
> I've spent several days trying to debug a deadlock using our local
> (not yet ready for upstream) driver for the J-Core SPI device and it
> seems to be a new deadlock in the SPI core caused by commit
> 556351f14e74 and unrelated to the particular driver. Commit
> 49023d2e4ead tried to solve a related deadlock problem, but there
> still seems to be a lock order issue and it's affecting SPI use even
> without the spi_flash_read optimization. The deadlock I'm observing
> has a kworker thread stuck in wait_for_completion called from
> spi_sync_locked (ultimately from mmc_rescan) and the completion is
> never finishing because this kworker thread has the bus locked while
> the spi master task has already started processing the queue but can't
> proceed because the bus lock is taken.
> 
> Anyone else seen this? Ideas for a proper fix?

Could you try 24c8cd1b081286("spi: fix possible deadlock between
internal bus locks and bus_lock_flag") from linux-next?

-- 
Regards
Vignesh