linux-kernel - Re: latest -git: WARNING: at arch/x86/kernel/ipi.c:123 send_IPI_mask

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:	Thu, 21 Aug 2008 20:36:59 -0400
From:	Dave Jones <davej@...hat.com>
To:	Vegard Nossum <vegard.nossum@...il.com>
Cc:	Andi Kleen <andi@...stfloor.org>,
	the arch/x86 maintainers <x86@...nel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: latest -git: WARNING: at arch/x86/kernel/ipi.c:123
	send_IPI_mask_bitmask+0xc3/0xe0()

On Wed, Aug 20, 2008 at 08:26:19AM +0200, Vegard Nossum wrote:
 > On Wed, Aug 20, 2008 at 3:39 AM, Andi Kleen <andi@...stfloor.org> wrote:
 > > On Tue, Aug 19, 2008 at 09:51:44PM +0200, Vegard Nossum wrote:
 > >> Hi,
 > >>
 > >> With latest -git (1fca25427482387689fa27594c992a961d98768f), I got
 > >> this on reading from /dev/cpu/*/* while hot-unplugging cpu1.
 > >
 > > It's generally known the oprofile doesn't support CPU hotplug well.
 > > Someone needs to make a project out of fixing it properly. Right now
 > > it's just a "don't do that when it hurts"
 > 
 > Hm. What you say is true, but this one in particular has nothing to do
 > with oprofile! It has something to do with reading /dev/cpu/*/msr
 > while hot-unplugging cpu1:
 > 
 >  [<c011733e>] msr_read+0x6e/0xa0
 >  [<c01a87b4>] vfs_read+0x94/0x130
 > 
 > I wasn't using oprofile when this happened. So I think it should also
 > be considered a separate issue. Though yes -- CPU hotplug in general
 > tends to break a lot of things.

>From my reading of the msr code, we check that the cpu is online in ->open,
but we never check it again, and also, we make no guarantees that it
won't go away before we ->read or even ->close it.

Would adding a get_cpu/put_cpu across the open/close solve this?
Peter?

	Dave

-- 
http://www.codemonkey.org.uk
--
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/