linux-kernel - Re: [PATCH] CDROM: replace jiffies busyloop with msleep

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Message-ID: <20070522112047.GS4705@kernel.dk>
Date:	Tue, 22 May 2007 13:20:49 +0200
From:	Jens Axboe <jens.axboe@...cle.com>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Jeff Garzik <jeff@...zik.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	LKML <linux-kernel@...r.kernel.org>,
	Alan Cox <alan@...rguk.ukuu.org.uk>
Subject: Re: [PATCH] CDROM: replace jiffies busyloop with msleep

On Tue, May 22 2007, Ingo Molnar wrote:
> 
> * Jeff Garzik <jeff@...zik.org> wrote:
> 
> > >@@ -1709,12 +1710,11 @@ static int __init sjcd_init(void)
> > > 	printk(KERN_INFO "SJCD: Resetting: ");
> > > 	sjcd_send_cmd(SCMD_RESET);
> > > 	for (i = 1000; i > 0 && !sjcd_status_valid; --i) {
> > >-		unsigned long timer;
> > >-
> > > 		/*
> > > 		 * Wait 10ms approx.
> > > 		 */
> > >-		for (timer = jiffies; time_before_eq(jiffies, timer););
> > >+		msleep(10);
> > >+
> > 
> > I always worry when I see code like this, wondering if there is some 
> > arcane reason that I cannot fathom, that is being removed.  You gotta 
> > wonder how long it has been since this driver was used, by anybody.
> > 
> > Oh well, I cannot find fault with the patch, paranoia worries aside.
> 
> well, while i dont have that hardware, i found this by booting an 
> allyesconfig bzImage which runs the code above, which locks up without 
> this change. And then it booted fine with this change. So arcane issues 
> aside, it does visibly improve things ;-)

But if you looked at the driver, you'd see 2 other identical busy loops
in the very same function :-)

-- 
Jens Axboe

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