Subject: Re: io_request_lock question (2.2)
To: baettig@scs.ch
Date: Fri, 8 Dec 2000 13:44:40 +0000 (GMT)
Cc: alan@lxorguk.ukuu.org.uk (Alan Cox), linux-kernel@vger.kernel.org
In-Reply-To: <200012080127.RAA13144@k2.llnl.gov> from "Reto Baettig" at Dec 07, 2000 05:27:56 PM
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Message-Id: <E144NpK-0003ti-00@the-village.bc.nu>
From: Alan Cox <alan@lxorguk.ukuu.org.uk>
Sender: linux-kernel-owner@vger.kernel.org

> 	spin_lock_irq(&io_request_lock);
> we finish the request and return to the add_request function which calls
> 	spin_unlock_irqrestore(&io_request_lock,flags);
> and restores the flags.     
> 
> Isn't it possible now that the flags which we restore are out of date now?
> Is this idiom the right one to use for 2.2?

It is fine for 2.2 as well.

The flags you restore are ok. It restores the interrupt state to the state it
was in when you were called. Think of save_flags/restore_flags as bracketing
regions of code (and being nestable in pairs). The only real bizarre rule is
that you cannot save_flags in one function and restore_flags in another without
upsetting DaveM - as it breaks on the sparc if you do that

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