linux-kernel - Re: Hang on large copy_from_user with PREEMPT

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Date:	Mon, 6 Apr 2015 21:36:22 +0200
From:	Borislav Petkov <bp@...en8.de>
To:	Sasha Levin <sasha.levin@...cle.com>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Rusty Russell <rusty@...tcorp.com.au>,
	Dave Jones <davej@...hat.com>, Michal Hocko <mhocko@...e.cz>,
	the arch/x86 maintainers <x86@...nel.org>
Subject: Re: Hang on large copy_from_user with PREEMPT_NONE

On Mon, Apr 06, 2015 at 03:08:24PM -0400, Sasha Levin wrote:
> Your patch just makes it hang in memset instead:
> 
> [  963.104556] NMI watchdog: BUG: soft lockup - CPU#1 stuck for 22s! [trinity-c224:9845]
> [  963.104556] Modules linked in:
> [  963.104556] irq event stamp: 3773324
> [  963.104556] hardirqs last  enabled at (3773323): [<ffffffffb7af8e3c>] restore_args+0x0/0x34
> [  963.104556] hardirqs last disabled at (3773324): [<ffffffffb7af919e>] apic_timer_interrupt+0x6e/0x80
> [  963.104556] softirqs last  enabled at (3773322): [<ffffffffad1f6589>] __do_softirq+0x709/0xd40
> [  963.104556] softirqs last disabled at (3773317): [<ffffffffad1f746d>] irq_exit+0x29d/0x320
> [  963.104556] CPU: 1 PID: 9845 Comm: trinity-c224 Not tainted 4.0.0-rc6-next-20150402-sasha-00039-ge0bdae3-dirty #2130
> [  963.104556] task: ffff8802a3560000 ti: ffff8802a3568000 task.ti: ffff8802a3568000
> [  963.104556] RIP: 0010:[<ffffffffaefbd173>]  [<ffffffffaefbd173>] memset_orig+0x33/0xb0

memset_orig?

Hmmm, your box doesn't set X86_FEATURE_REP_GOOD. And looking at your
dmesg I can see why - that's a kvm guest and you're emulating some qemu
-cpu kvm64 or so thing, AFAICT.

Can you give me your full command line?

Btw, maybe you should try to trigger this on real metal, just in case,
to rule out virt issues. Or have you, already?

Thanks.

-- 
Regards/Gruss,
    Boris.

ECO tip #101: Trim your mails when you reply.
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