linux-kernel - Re: frequent lockups in 3.18rc4

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Message-ID: <20141115024042.GA18015@redhat.com>
Date:	Fri, 14 Nov 2014 21:40:42 -0500
From:	Dave Jones <davej@...hat.com>
To:	Thomas Gleixner <tglx@...utronix.de>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	the arch/x86 maintainers <x86@...nel.org>
Subject: Re: frequent lockups in 3.18rc4

On Sat, Nov 15, 2014 at 01:36:41AM +0100, Thomas Gleixner wrote:
 > On Fri, 14 Nov 2014, Dave Jones wrote:
 > 
 > > On Fri, Nov 14, 2014 at 11:55:30PM +0100, Thomas Gleixner wrote:
 > >  
 > >  > So this looks more like a smp function call fuckup.
 > >  > 
 > >  > I assume Dave is running that stuff on KVM. So it might be worth while
 > >  > to look at the IPI magic there.
 > > 
 > > no, bare metal.
 > 
 > Ok, but that does not change the fact that we are stuck in
 > smp_function_call land.
 > 
 > Enabling softlockup_all_cpu_backtrace will probably not help much as
 > we will end up waiting for csd_lock again :(
 > 
 > Is the machine still accesible when this happens? If yes, we might
 > enable a few trace points and functions and read out the trace
 > buffer. If not, we could just panic the machine and dump the trace
 > buffer over serial.

No, it wedges solid. Even though it says something like "CPU3 locked up",
aparently all cores also get stuck.
9 times out of 10 it doesn't stay alive long enough to even get the full
trace out over usb-serial.

	Dave

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