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From: Bart Van Assche <bvanassche@acm.org>
To: Tejun Heo <tj@kernel.org>
Cc: linux-scsi <linux-scsi@vger.kernel.org>,
	James Bottomley <jbottomley@parallels.com>,
	Mike Christie <michaelc@cs.wisc.edu>,
	Jens Axboe <axboe@kernel.dk>, Chanho Min <chanho.min@lge.com>
Subject: Re: [PATCH 1/7] block: Avoid that blk_drain_queue() finishes early
Date: Mon, 29 Oct 2012 15:35:50 +0100	[thread overview]
Message-ID: <508E9446.1040700@acm.org> (raw)
In-Reply-To: <20121029015234.GD5171@htj.dyndns.org>

On 10/29/12 02:52, Tejun Heo wrote:
> On Sun, Oct 28, 2012 at 06:47:22PM -0700, Tejun Heo wrote:
>> On Fri, Oct 26, 2012 at 02:01:23PM +0200, Bart Van Assche wrote:
>>> Code like "drain |= q->nr_rqs[i]" might result in blk_drain_queue()
>>> to finish early if the expression at the RHS is a multiple of 256
>>> since the drain variable is only eight bits wide. Avoid this by
>>> changing the type of the drain variable from bool into unsigned.
>>
>> No, it doesn't happen that way.  One of the reasons we have bool at
>> all is to avoid this type of problems caused by implicit type-casting.
>>
>> Why do you keep pushing this?  It's WRONG.  Please drop it.
>
>>From C99 std draft.
>
>   6.3 Conversions
>   6.3.1.2 Boolean type
>
>    When any scalar value is converted to _Bool, the result is 0 if the
>    value compares equal to 0; otherwise, the result is 1.
>
> It doesn't care the width or signedness of the type being converted.
> If the origin value equals zero, it converts to 0; otherwise 1.

For one or another reason I was assuming that bool was a typedef for 
unsigned char. But you are right, it's a synonym for the C99 type _Bool 
so I'll drop this patch.

Bart.


  reply	other threads:[~2012-10-29 14:35 UTC|newest]

Thread overview: 24+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-10-26 12:00 [PATCH 0/7 v5] More device removal fixes Bart Van Assche
2012-10-26 12:01 ` [PATCH 1/7] block: Avoid that blk_drain_queue() finishes early Bart Van Assche
2012-10-29  1:47   ` Tejun Heo
2012-10-29  1:52     ` Tejun Heo
2012-10-29 14:35       ` Bart Van Assche [this message]
2012-10-26 12:02 ` [PATCH 2/7] block: Let blk_drain_queue() caller obtain the queue lock Bart Van Assche
2012-10-29  1:55   ` Tejun Heo
2012-10-26 12:02 ` [PATCH 3/7] block: Rename queue dead flag Bart Van Assche
2012-10-26 12:03 ` [PATCH 4/7] block: Avoid that request_fn is invoked on a dead queue Bart Van Assche
2012-10-29  1:59   ` Tejun Heo
2012-10-26 12:04 ` [PATCH 5/7] block: Make blk_cleanup_queue() wait until request_fn finished Bart Van Assche
2012-10-29  2:00   ` Tejun Heo
2012-10-26 12:05 ` [PATCH 6/7] Fix race between starved list processing and device removal Bart Van Assche
2012-10-28 18:01   ` Zhuang, Jin Can
2012-10-29 14:32     ` Bart Van Assche
2012-10-30  5:40       ` Zhuang, Jin Can
2012-11-02 10:48         ` Bart Van Assche
2012-11-21 11:06           ` Bart Van Assche
     [not found]         ` <026701cdb8c3$d2e3cb50$78ab61f0$@min@lge.com>
2012-11-21 12:10           ` Bart Van Assche
2012-10-29  2:07   ` Tejun Heo
2012-10-26 12:05 ` [PATCH 7/7] Remove get_device() / put_device() pair from scsi_request_fn() Bart Van Assche
2012-10-29  2:08   ` Tejun Heo
2012-11-23 10:37 ` [PATCH 0/7 v5] More device removal fixes Bart Van Assche
2012-11-26 17:19   ` Bart Van Assche

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