linux-kernel - Re: [PATCH] x86: serialize EFI time accesses on rtc

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Message-ID: <20110719175432.GA23018@srcf.ucam.org>
Date:	Tue, 19 Jul 2011 18:54:32 +0100
From:	Matthew Garrett <mjg59@...f.ucam.org>
To:	Rakib Mullick <rakib.mullick@...il.com>
Cc:	Jan Beulich <JBeulich@...ell.com>, mingo@...e.hu,
	tglx@...utronix.de, hpa@...or.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] x86: serialize EFI time accesses on rtc_lock

On Tue, Jul 19, 2011 at 11:32:05PM +0600, Rakib Mullick wrote:

> If I'm not missing anything, this implementation (serialization) could
> be simpler by holding rtc_lock at the time of calling those functions.
> I mean, holding rtc_lock before calling EFI services
> virt_efi_get/set_time and virt_efi_get/set_wakeup_time - something
> like below:
> 
>              spin_lock_irqsave(&rtc_lock, flags);
>              efi.get_time = virt_efi_get_time;
>              efi.set_time = virt_efi_set_time;
>              efi.get_wakeup_time = virt_efi_get_wakeup_time;
>              efi.set_wakeup_time = virt_efi_set_wakeup_time;
>             spin_unlock_irqrestore(&rtc_lock, flags);

That's just assigning some function pointers, not actually making the 
calls. There's potentially several routes to each of the calls, so it 
makes sense to do the locking there.

-- 
Matthew Garrett | mjg59@...f.ucam.org
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