linux-kernel - Re: [PATCH 1/5] HDQ Driver for OMAP2430/3430

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Message-ID: <20081013134239.GB13565@2ka.mipt.ru>
Date:	Mon, 13 Oct 2008 17:42:40 +0400
From:	Evgeniy Polyakov <johnpol@....mipt.ru>
To:	Madhusudhan Chikkature <madhu.cr@...com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	"Gadiyar, Anand" <gadiyar@...com>, linux-kernel@...r.kernel.org,
	linux-omap@...r.kernel.org
Subject: Re: [PATCH 1/5] HDQ Driver for OMAP2430/3430

Hi.

On Mon, Oct 13, 2008 at 06:55:43PM +0530, Madhusudhan Chikkature (madhu.cr@...com) wrote:
> >> +static int hdq_write_byte(struct hdq_data *hdq_data, u8 val, u8 *status)
> >> +{
> >> +       int ret;
> >> +       u8 tmp_status;
> >> +       unsigned long irqflags;
> >> +
> >> +       *status = 0;
> >> +
> >> +       spin_lock_irqsave(&hdq_data->hdq_spinlock, irqflags);
> >> +       /* clear interrupt flags via a dummy read */
> >> +       hdq_reg_in(hdq_data, OMAP_HDQ_INT_STATUS);
> >> +       /* ISR loads it with new INT_STATUS */
> >> +       hdq_data->hdq_irqstatus = 0;
> >> +       spin_unlock_irqrestore(&hdq_data->hdq_spinlock, irqflags);
> >> +
> >> +       hdq_reg_out(hdq_data, OMAP_HDQ_TX_DATA, val);
> >> +
> >> +       /* set the GO bit */
> >> +       hdq_reg_merge(hdq_data, OMAP_HDQ_CTRL_STATUS, OMAP_HDQ_CTRL_STATUS_GO,
> >> +               OMAP_HDQ_CTRL_STATUS_DIR | OMAP_HDQ_CTRL_STATUS_GO);
> >> +       /* wait for the TXCOMPLETE bit */
> >> +       ret = wait_event_interruptible_timeout(hdq_wait_queue,
> >> +               hdq_data->hdq_irqstatus, OMAP_HDQ_TIMEOUT);
> >> +       if (ret < 0) {
> >> +               dev_dbg(hdq_data->dev, "wait interrupted");
> >> +               return -EINTR;
> >> +       }
> > 
> > Is this desirable?  The user hits ^C and the driver bails out?
> > 
> > I assume so, but was this tested?
> 
> Andrew, What is the test scenario you mean here? A user hitting ^C when the driver is waiting for the TXCOMPLETE bit?

Just plain return looks suspicious, is there some kind of a race between
calling code (which for example frees hdq_data) and the path, which sets
the bit and wakes up this thread?

-- 
	Evgeniy Polyakov
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