Hi Russell, On Fri, Jun 01, 2018 at 12:00:16PM +0100, Russell King wrote: > Executing loops such as: > > while (1) > cpu_relax(); > > with interrupts disabled results in a livelock of the entire system, > as other CPUs are prevented making progress. This is most noticable > as a failure of crashdump kexec, which stops just after issuing: > > Loading crashdump kernel... > > to the system console. Two other locations of these loops within the > ARM code have been identified and fixed up. Can you confirm that this only happens if CONFIG_ARM_ERRATA_754327=y? The only erratum I can find for A9 that matches this behaviour exists when the body of the tight loop contains a DMB and some of the possible workarounds are: - Add ten NOPs after the DMB - Use DSB instead of DMB in the tight loop - Set bit 16 in the diagnostic control register (p15, c1, 5, 0, c0, 1) WFE is probably fine (the write-up isn't clear), but if this only occurs due to CONFIG_ARM_ERRATA_754327=y it would be nice to mitigate it in the alternative cpu_relax() definition itself, which isn't generally possible with WFE. Will -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
