linux-kernel - Re: NMI hardlock stacktrace deadlock [was Re: Linux 5.2-rc5]

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Message-ID: <20190626082609.5c8489f0@gandalf.local.home>
Date:   Wed, 26 Jun 2019 08:26:09 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Josh Poimboeuf <jpoimboe@...hat.com>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Chris Wilson <chris@...is-wilson.co.uk>,
        Linux List Kernel Mailing <linux-kernel@...r.kernel.org>,
        Thomas Gleixner <tglx@...utronix.de>
Subject: Re: NMI hardlock stacktrace deadlock [was Re: Linux 5.2-rc5]

On Mon, 24 Jun 2019 22:03:45 -0500
Josh Poimboeuf <jpoimboe@...hat.com> wrote:

> Looking at the dmesg, panic_on_oops doesn't seem to be enabled: it went
> through the rewind_stack_do_exit() path instead of the panic() path.  So
> the system is apparently not configured to reboot on oops.

"Command line: BOOT_IMAGE=/boot/drm_intel root=/dev/sda1 rootwait fsck.repair=yes intel_iommu=igfx_off nmi_watchdog=panic,auto panic=5 softdog.soft_panic=5 drm.debug=0xe log_buf_len=1M 3 ro"

> 
> So I'd say the hang was presumably caused by a lock held by the oopsing
> code.  So it looks normal to me, other than the original oops.
> 

Looks like its missing "oops=panic", as the documentation says:


        oops=panic      Always panic on oopses. Default is to just kill the
                        process, but there is a small probability of
                        deadlocking the machine.
                        This will also cause panics on machine check exceptions.
                        Useful together with panic=30 to trigger a reboot.

-- Steve