linux-kernel - Re: [PATCH] drivers/mmc/mmc.c: Replacing yield() with a better alternative

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Message-ID: <452DD88E.4030707@yahoo.com.au>
Date:	Thu, 12 Oct 2006 15:54:22 +1000
From:	Nick Piggin <nickpiggin@...oo.com.au>
To:	Arjan van de Ven <arjan@...radead.org>
CC:	Amol Lad <amol@...ismonetworks.com>,
	linux kernel <linux-kernel@...r.kernel.org>,
	kernel Janitors <kernel-janitors@...ts.osdl.org>
Subject: Re: [PATCH] drivers/mmc/mmc.c: Replacing yield() with a better	alternative

Arjan van de Ven wrote:
> On Wed, 2006-10-11 at 18:15 +0530, Amol Lad wrote:
> 
>>In 2.6, the semantics of calling yield() changed from "sleep for a
>>bit" to "I really don't want to run for a while".  This matches POSIX
>>better, but there's a lot of drivers still using yield() when they mean
>>cond_resched(), schedule() or even schedule_timeout().
>>
>>For this driver cond_resched() seems to be a better
>>alternative
>>
> 
> 
> are you sure?
> 
> 
>>Tested compile only
>>
>>Signed-off-by: Amol Lad <amol@...ismonetworks.com>
>>---
>>diff -uprN -X linux-2.6.19-rc1-orig/Documentation/dontdiff linux-2.6.19-rc1-orig/drivers/mmc/mmc.c linux-2.6.19-rc1/drivers/mmc/mmc.c
>>--- linux-2.6.19-rc1-orig/drivers/mmc/mmc.c	2006-10-05 14:00:46.000000000 +0530
>>+++ linux-2.6.19-rc1/drivers/mmc/mmc.c	2006-10-11 17:57:02.000000000 +0530
>>@@ -454,7 +454,7 @@ static void mmc_deselect_cards(struct mm
>> static inline void mmc_delay(unsigned int ms)
>> {
>> 	if (ms < HZ / 1000) {
>>-		yield();
>>+		cond_resched();
>> 		mdelay(ms);
> 
> 
> 
> this probably wants msleep(), especially with hrtimers comming up; there
> the sleeps are always exact...

The condition looks broken too. It should be
if (ms < 1000 / HZ) {...}

Shouldn't it?
-- 
SUSE Labs, Novell Inc.
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