On 07/26/2013 04:49 AM, Will Deacon wrote: > [Adding Stephen Warren since he has been working in this area] > > On Fri, Jul 26, 2013 at 06:41:27AM +0100, vijay.kilari at gmail.com wrote: >> From: Vijaya Kumar K <Vijaya.Kumar at caviumnetworks.com> >> >> In case of normal kexec kernel load, all cpu's are offlined >> before calling machine_kexec() under kernel_kexec() function. >> But in case crash panic cpus are relaxed in >> machine_crash_nonpanic_core() SMP function but not offlined. >> >> When crash kernel is loaded with kexec and on panic trigger >> machine_kexec() checks for number of cpus online. >> If more than one cpu is online machine_kexec() fails to load >> with below error >> >> kexec: error: multiple CPUs still online >> >> In machine_crash_nonpanic_core() SMP function, offline CPU >> before cpu_relax >> diff --git a/arch/arm/kernel/machine_kexec.c b/arch/arm/kernel/machine_kexec.c >> @@ -73,6 +73,7 @@ void machine_crash_nonpanic_core(void *unused) >> crash_save_cpu(®s, smp_processor_id()); >> flush_cache_all(); >> >> + set_cpu_online(smp_processor_id(), false); >> atomic_dec(&waiting_for_crash_ipi); >> while (1) >> cpu_relax(); > > Ok, I guess this will work since the new kernel is loaded somewhere higher > in memory and the crashed kernel will stick around, so the non-crashing CPUs > can sit around spinning. Does a kernel that's used as the crash kernel guarantee: * Never to re-use the memory that was used by the previous kernel, so that the spin loop code/data won't be corrupted, ever, no matter how long the crash recovery kernel runs. * Not use SMP, so there's never a need to re-activate the non-boot CPUs, which might not work if they aren't truly disabled but rather just running a pin loop?
