On 07/25/2013 11:41 PM, 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. I'm not sure that's true, unless perhaps you have CONFIG_KEXEC_JUMP enabled? > 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); I'm not familiar with that API, but it looks like it's just setting the *current* CPU offline. That sounds problematic for two reasons: 1) Setting the current CPU offline sounds like a bad idea; after all, code is still running on it. Presumably you want to offline all other CPUs. 2) On a dual-CPU system, I guess this will leave a single CPU marked online, and hence satisfy the test in machine_kexec(). However, on a quad-core system, won't this just reduce the online CPU count from 4 to 3 and hence the test in machine_kexec() will still fail? Can't you call disable_nonboot_cpus() from machine_crash_nonpanic_core() just like machine_shutdown() does?
