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. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
