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From: Jim Nelson <james4765@verizon.net>
To: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: kernel-janitors@lists.osdl.org,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	akpm@osdl.org
Subject: [KJ] Re: [PATCH] pcxx: replace cli()/sti()
Date: Mon, 20 Dec 2004 21:51:39 +0000	[thread overview]
Message-ID: <41C7496B.4000401@verizon.net> (raw)
In-Reply-To: <1103574222.31479.12.camel@localhost.localdomain>

[-- Attachment #1: Type: text/plain, Size: 823 bytes --]

Alan Cox wrote:
> On Llu, 2004-12-20 at 14:59, Alan Cox wrote:
> 
>>On Gwe, 2004-12-17 at 22:34, James Nelson wrote:
>>
>>>-	save_flags(flags);
>>>-	cli();
>>>+	spin_lock_irqsave(&pcxx_lock, flags);
>>> 	del_timer_sync(&pcxx_timer);
>>
>>Not safe if the lock is grabbed by the timer between the lock and the
>>irqsave as it will spin on another cpu and the timer delete will never
>>finish.
> 
> 
> Error between brain and keyboard
> 
> Between the lock and the timer_delete of course
> 

Right.

Go ahead and ignore that set of cli()/sti() patches - I'll have to take them a 
little slower, checking for potential deadlocks and other nastiness.

I'll try again in a week or so - gotta finish "The Design of the Unix Operating 
System" first.  Love early Xmas presents from my aunt, the mainframe systems 
programmer... :)

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WARNING: multiple messages have this Message-ID (diff)
From: Jim Nelson <james4765@verizon.net>
To: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: kernel-janitors@lists.osdl.org,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	akpm@osdl.org
Subject: Re: [PATCH] pcxx: replace cli()/sti() with	spin_lock_irqsave()/spin_unlock_irqrestore()
Date: Mon, 20 Dec 2004 16:51:39 -0500	[thread overview]
Message-ID: <41C7496B.4000401@verizon.net> (raw)
In-Reply-To: <1103574222.31479.12.camel@localhost.localdomain>

Alan Cox wrote:
> On Llu, 2004-12-20 at 14:59, Alan Cox wrote:
> 
>>On Gwe, 2004-12-17 at 22:34, James Nelson wrote:
>>
>>>-	save_flags(flags);
>>>-	cli();
>>>+	spin_lock_irqsave(&pcxx_lock, flags);
>>> 	del_timer_sync(&pcxx_timer);
>>
>>Not safe if the lock is grabbed by the timer between the lock and the
>>irqsave as it will spin on another cpu and the timer delete will never
>>finish.
> 
> 
> Error between brain and keyboard
> 
> Between the lock and the timer_delete of course
> 

Right.

Go ahead and ignore that set of cli()/sti() patches - I'll have to take them a 
little slower, checking for potential deadlocks and other nastiness.

I'll try again in a week or so - gotta finish "The Design of the Unix Operating 
System" first.  Love early Xmas presents from my aunt, the mainframe systems 
programmer... :)

  reply	other threads:[~2004-12-20 21:51 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2004-12-17 22:34 [KJ] [PATCH] pcxx: replace cli()/sti() with James Nelson
2004-12-17 22:34 ` [PATCH] pcxx: replace cli()/sti() with spin_lock_irqsave()/spin_unlock_irqrestore() James Nelson
2004-12-20 14:59 ` [KJ] Re: [PATCH] pcxx: replace cli()/sti() with Alan Cox
2004-12-20 14:59   ` [PATCH] pcxx: replace cli()/sti() with spin_lock_irqsave()/spin_unlock_irqrestore() Alan Cox
2004-12-20 17:27   ` [KJ] Re: [PATCH] pcxx: replace cli()/sti() with Matthew Wilcox
2004-12-20 17:27     ` [KJ] Re: [PATCH] pcxx: replace cli()/sti() with spin_lock_irqsave()/spin_unlock_irqrestore() Matthew Wilcox
2004-12-20 20:23   ` [KJ] Re: [PATCH] pcxx: replace cli()/sti() with Alan Cox
2004-12-20 20:23     ` [PATCH] pcxx: replace cli()/sti() with spin_lock_irqsave()/spin_unlock_irqrestore() Alan Cox
2004-12-20 21:51     ` Jim Nelson [this message]
2004-12-20 21:51       ` Jim Nelson

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