linux-kernel - Re: [PATCH 1/3] net: ethernet: ti: cpdma: fix lockup in cpdma_ctlr

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Date:	Sat, 23 Jul 2016 09:24:55 +0300
From:	Ivan Khoronzhuk <ivan.khoronzhuk@...aro.org>
To:	Grygorii Strashko <grygorii.strashko@...com>,
	"David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org,
	Mugunthan V N <mugunthanvnm@...com>
Cc:	Sekhar Nori <nsekhar@...com>, linux-kernel@...r.kernel.org,
	linux-omap@...r.kernel.org
Subject: Re: [PATCH 1/3] net: ethernet: ti: cpdma: fix lockup in
 cpdma_ctlr_destroy()



On 22.07.16 16:58, Grygorii Strashko wrote:
> Fix deadlock in cpdma_ctlr_destroy() which is triggered now on
> cpsw module removal:
>  cpsw_remove()
>  - cpdma_ctlr_destroy()
>    - spin_lock_irqsave(&ctlr->lock, flags)
>    - cpdma_ctlr_stop()
>      - spin_lock_irqsave(&ctlr->lock, flags); <- deadlock
>    - cpdma_chan_destroy()
>      - spin_lock_irqsave(&ctlr->lock, flags); <- deadlock
>
> The issue has not been observed before because CPDMA channels have
> been destroyed manually by CPSW until commit d941ebe88a41 ("net:
> ethernet: ti: cpsw: use destroy ctlr to destroy channels") was merged.
>
> Signed-off-by: Grygorii Strashko <grygorii.strashko@...com>
> ---
>  drivers/net/ethernet/ti/davinci_cpdma.c | 2 --
>  1 file changed, 2 deletions(-)
>
> diff --git a/drivers/net/ethernet/ti/davinci_cpdma.c b/drivers/net/ethernet/ti/davinci_cpdma.c
> index a68652a..89242e9 100644
> --- a/drivers/net/ethernet/ti/davinci_cpdma.c
> +++ b/drivers/net/ethernet/ti/davinci_cpdma.c
> @@ -436,7 +436,6 @@ int cpdma_ctlr_destroy(struct cpdma_ctlr *ctlr)
>  	if (!ctlr)
>  		return -EINVAL;
>
> -	spin_lock_irqsave(&ctlr->lock, flags);
Should ctlr->state be checked under lock?
Seems like here should be used unlocked static versions of
cpdma_ctlr_stop() and cpdma_chan_destroy() instead.

>  	if (ctlr->state != CPDMA_STATE_IDLE)
>  		cpdma_ctlr_stop(ctlr);
>
> @@ -444,7 +443,6 @@ int cpdma_ctlr_destroy(struct cpdma_ctlr *ctlr)
>  		cpdma_chan_destroy(ctlr->channels[i]);
>
>  	cpdma_desc_pool_destroy(ctlr->pool);
> -	spin_unlock_irqrestore(&ctlr->lock, flags);
>  	return ret;
>  }
>  EXPORT_SYMBOL_GPL(cpdma_ctlr_destroy);
>

-- 
Regards,
Ivan Khoronzhuk