linux-kernel - Re: Reworking suspend-resume sequence (was: Re: PCI PM: Restore standard config registers of all devices early)

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <alpine.LFD.2.00.0902030955370.3247@localhost.localdomain>
Date:	Tue, 3 Feb 2009 09:59:34 -0800 (PST)
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
cc:	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Jesse Barnes <jesse.barnes@...el.com>,
	Andreas Schwab <schwab@...e.de>, Len Brown <lenb@...nel.org>,
	Ingo Molnar <mingo@...e.hu>
Subject: Re: Reworking suspend-resume sequence (was: Re: PCI PM: Restore
 standard config registers of all devices early)



On Tue, 3 Feb 2009, Rafael J. Wysocki wrote:
>
> Having reconsidered it, I think that the "loop of disable_irq()" may be
> problematic due to MSI/MSI-X and devices that are put into D3 during the
> "normal" suspend.  That is, we shouldn't try to mask MSI/MSI-X for devices in
> D3

Rafael, you seem to be confused about what "disable_irq()" does.

It does not touch the driver hardware AT ALL. It literally just touches 
the interrupt controller, and even that only indirectly.

What disable_irq() does it literally:

	void disable_irq_nosync(unsigned int irq)
	{
	        struct irq_desc *desc = irq_to_desc(irq);
	        unsigned long flags;
  
	        if (!desc)
	                return;

	        spin_lock_irqsave(&desc->lock, flags);
	        if (!desc->depth++) {
	                desc->status |= IRQ_DISABLED;
	                desc->chip->disable(irq);
	        }
	        spin_unlock_irqrestore(&desc->lock, flags);
	}

and then it does a "synchronize_irq()" to wait to make sure that there are 
no pending ones.

And in many cases, even the

	desc->chip->disable(irq);

doesn't actually _do_ anything - we'll quite possibly continue to take the 
interrupt, and only when the interrupt happens will it see the "oh, 
IRQ_DISABLED is set" thing, and do something about it.

So don't worry about putting devices in D3 - disable_irq() will not care 
AT ALL whether the device is alive or not, and will never try to touch it 
anyway.

		Linus
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/