linux-kernel - Re: 2.6.24-git: kmap_atomic() WARN

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]

Date:	Tue, 26 Feb 2008 10:19:28 -0800
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Jeff Garzik <jgarzik@...ox.com>
Cc:	Ingo Molnar <mingo@...e.hu>, Thomas Gleixner <tglx@...utronix.de>,
	Björn Steinbrink <B.Steinbrink@....de>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: 2.6.24-git: kmap_atomic() WARN_ON()

On Tue, 26 Feb 2008 11:32:24 -0500 Jeff Garzik <jgarzik@...ox.com> wrote:

> Ingo Molnar wrote:
> > * Jeff Garzik <jgarzik@...ox.com> wrote:
> > 
> >> +	unsigned long flags;
> >> +
> >> +	local_irq_save(flags);
> > 
> > hm, couldnt we attach the irq disabling to some spinlock, in a natural 
> > way? Explicit flags fiddling is a PITA once we do things like threaded 
> > irq handlers, -rt, etc.
> 
> Attaching the irq disabling to some spinlock is what would be 
> artificial...  See the ahci.c patch earlier in this thread.  It is taken 
> without spin_lock_irqsave() in the interrupt handler, and there is no 
> reason to disable interrupts for the entirety of the interrupt handler 
> run -- only the part where we call kmap.
> 
> This is only being done to satisfy kmap_atomic's requirements, not libata's.
> 
> I could add a "kmap lock" but that just seems silly.
> 

It's a bit sad to disable interupts across a memset (how big is it?) just
for the small proportion of cases which are accessing a highmem page.

What you could do is to add an `unsigned long *flags' arg to
ata_scsi_rbuf_get() and ata_scsi_rbuf_put(), and then, in
ata_scsi_rbuf_get() do

	if (PageHighmem(page))
		local_irq_disable(*flags);


--
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/