On 07/30/2018 11:57 AM, Will Deacon wrote: > On Mon, Jul 30, 2018 at 11:46:24AM -0500, Dave Kleikamp wrote: >> On 07/30/2018 11:22 AM, Will Deacon wrote: >>> On Mon, Jul 30, 2018 at 05:16:42PM +0100, Catalin Marinas wrote: >>>> On Mon, Jul 30, 2018 at 10:29:21AM -0500, Dave Kleikamp wrote: >>>>> machine_kexec flushes the reboot_code_buffer from the icache >>>>> after stopping the other cpus. >>>>> >>>>> Commit 3b8c9f1cdfc5 ("arm64: IPI each CPU after invalidating the I-cache >>>>> for kernel mappings") added an IPI call to flush_icache_range, which >>>>> causes a hang here, so replace the call with __flush_icache_range >>>> >>>> While machine_kexec() may be called with interrupts disabled (IIUC) and >>>> we shouldn't IPI other CPUs, I don't understand why it hangs here. Are >>>> there any other CPUs online at this point? >>> >>> The BUG_ON and WARN_ON at the start of machine_kexec() suggest to me that >>> this should only happen if we're kexec'ing a crash kernel and >>> smp_crash_stop_failed(). Is that something we need to care about? >> >> I observed the hang trying to kexec a crash kernel and I did not see the >> warning that smp_crash_stop_failed(). I'm not exactly sure why >> flush_icache_range() hung (but it did), but I think that >> __flush_icache_range() makes more sense here anyway. > > Yeah, I'll pick the patch up, but it would be nice to understand the > failure case you observed.
I'll dig a little deeper. Thanks, Dave > > Will >