linux-kernel - Re: [PATCH v3 04/36] mtd: st_spi_fsm: Supply framework for device requests

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Date:	Fri, 13 Dec 2013 14:35:00 +0000
From:	Angus Clark <angus.clark@...com>
To:	Brian Norris <computersforpeace@...il.com>
Cc:	Lee Jones <lee.jones@...aro.org>,
	<linux-arm-kernel@...ts.infradead.org>,
	<linux-kernel@...r.kernel.org>, <dwmw2@...radead.org>,
	<linus.walleij@...aro.org>, <linux-mtd@...ts.infradead.org>,
	Angus CLARK <angus.clark@...com>
Subject: Re: [PATCH v3 04/36] mtd: st_spi_fsm: Supply framework for device
 requests

On 12/10/2013 08:19 PM, Brian Norris wrote:
> On Fri, Nov 29, 2013 at 12:18:53PM +0000, Lee Jones wrote:
>> --- a/drivers/mtd/devices/st_spi_fsm.c
>> +static void stfsm_wait_seq(struct stfsm *fsm)
>> +{
>> +	unsigned long timeo = jiffies + HZ;
>> +
>> +	while (time_before(jiffies, timeo)) {
>> +		if (stfsm_is_idle(fsm))
>> +			return;
>> +
>> +		cond_resched();
>> +	}
>> +
>> +	dev_err(fsm->dev, "timeout on sequence completion\n");
> 
> I believe the timeout logic is incorrect. What if we wait a "long time"
> to call stfsm_wait_seq() (due to scheduling, or otherwise)? Then the
> while loop might not even run once (time_before(x, y) is false). Or what
> if cond_resched() waits for a long time...
> 
> So you need an extra check of stfsm_is_idle() after the while loop,
> before you declare a timeout.

Yes, good catch, this needs to updated.

Cheers,

Angus
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