On 16/10/14 13:23, Russell King - ARM Linux wrote:

On Thu, Oct 16, 2014 at 10:23:52AM +0100, Daniel Thompson wrote:

quoted

On 14/10/14 23:37, Daniel Drake wrote:

quoted

I'm testing your patches on Exynos4412 and I guess in their current
state they don't go quite this deep, as the only callers of
trigger_all_cpu_backtrace() are sysrq, hung_task and spinlock debug
code - none of which seem as fail-safe as a trigger like a
pre-programmed watchdog NMI interrupt would be.

Do I need to find a way to get CONFIG_FIQ available on this platform
first? and/or CONFIG_HARDLOCKUP_DETECTOR?

You need CONFIG_FIQ working first. Be aware that this may be impossible
on Exynos unless you control the TrustZone. For this reason most of my
development is on Freescale i.MX6 (because i.MX6 boots in secure mode).

CONFIG_FIQ enables the legacy FIQ code which is unsuitable for use on
SMP, so that should not be a requirement.

Sorry. That was rather stupid phrasing on my part.

What I mean is that before doing any other work related to FIQ one
should establish that the platform really is using FIQ to trigger
backtraces! On platforms where FIQ cannot be supported the code falls
back to using IRQs (making the IRQ handling easily spotted in the
backtrace).