Messages in this thread | | | Date | Thu, 16 Oct 2014 13:23:23 +0100 | From | Russell King - ARM Linux <> | Subject | Re: [PATCH 3.17-rc4 v7 0/6] arm: Implement arch_trigger_all_cpu_backtrace |
| |
On Thu, Oct 16, 2014 at 10:23:52AM +0100, Daniel Thompson wrote: > On 14/10/14 23:37, Daniel Drake wrote: > > 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.
We still need to validate all the code we're proposing to run in FIQ context does not violate any locking. IRQ-safe locks will do not prevent FIQs occuring, and using IRQ-safe locks which are also taken in the FIQ path /will/ cause deadlocks. So, we need to ensure that the perf internals are safe for this.
Lastly, platforms running in non-secure mode most likely will not be able to take /any/ advantage from the FIQ stuff because FIQs will likely only be available to the secure firmware.
-- FTTC broadband for 0.8mile line: currently at 9.5Mbps down 400kbps up according to speedtest.net.
| |