linux-kernel - Re: [PATCH 1/2] mfd: rtsx_usb: Fix runtime PM deadlock

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Message-ID: <20150120160736.GM13701@x1>
Date:	Tue, 20 Jan 2015 16:07:36 +0000
From:	Lee Jones <lee.jones@...aro.org>
To:	Roger Tseng <rogerable@...ltek.com>
Cc:	Samuel Ortiz <sameo@...ux.intel.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"driverdev-devel@...uxdriverproject.org" 
	<driverdev-devel@...uxdriverproject.org>,
	Wei_wang <wei_wang@...lsil.com.cn>,
	"micky_ching@...lsil.com.cn" <micky_ching@...lsil.com.cn>
Subject: Re: [PATCH 1/2] mfd: rtsx_usb: Fix runtime PM deadlock

On Tue, 20 Jan 2015, Roger Tseng wrote:

> On Mon, 2015-01-19 at 09:45 +0000, Lee Jones wrote:
> > On Thu, 15 Jan 2015, Roger Tseng wrote:
> > 
> > > sd_set_power_mode() in derived module drivers/mmc/host/rtsx_usb_sdmmc.c
> > > acquires dev_mutex and then calls pm_runtime_get_sync() to make sure the
> > > device is awake while initializing a newly inserted card. Once it is
> > > called during suspending state and explicitly before rtsx_usb_suspend()
> > > acquires the same dev_mutex, both routine deadlock and further hang the
> > > driver because pm_runtime_get_sync() waits the pending PM operations.
> > > 
> > > Fix this by using an empty suspend method. mmc_core always turns the
> > > LED off after a request is done and thus it is ok to remove the only
> > > rtsx_usb_turn_off_led() here.
> > > 
> > > Cc: <stable@...r.kernel.org> # v3.16+
> > > Fixes: 730876be2566 ("mfd: Add realtek USB card reader driver")
> > > Signed-off-by: Roger Tseng <rogerable@...ltek.com>
> > > ---
> > >  drivers/mfd/rtsx_usb.c | 9 ---------
> > >  1 file changed, 9 deletions(-)
> > 
> > Applied, thanks.
> > 
> I'm sorry but build bot from Intel just reported me that I forgot to
> delete an unused variable "ucr" between two commits. My bad.
> 
> Do I have a chance to send v2?

You're lucky I'm in a good mood. ;)

I fixed it already.

> > > diff --git a/drivers/mfd/rtsx_usb.c b/drivers/mfd/rtsx_usb.c
> > > index dbdd0faeb6ce..076694126e5d 100644
> > > --- a/drivers/mfd/rtsx_usb.c
> > > +++ b/drivers/mfd/rtsx_usb.c
> > > @@ -687,15 +687,6 @@ static int rtsx_usb_suspend(struct usb_interface *intf, pm_message_t message)
> > >  	dev_dbg(&intf->dev, "%s called with pm message 0x%04x\n",
> > >  			__func__, message.event);
> > >  
> > > -	/*
> > > -	 * Call to make sure LED is off during suspend to save more power.
> > > -	 * It is NOT a permanent state and could be turned on anytime later.
> > > -	 * Thus no need to call turn_on when resunming.
> > > -	 */
> > > -	mutex_lock(&ucr->dev_mutex);
> > > -	rtsx_usb_turn_off_led(ucr);
> > > -	mutex_unlock(&ucr->dev_mutex);
> > > -
> > >  	return 0;
> > >  }
> > >  
> > 
> 

-- 
Lee Jones
Linaro STMicroelectronics Landing Team Lead
Linaro.org │ Open source software for ARM SoCs
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