Hi Corey, > From: Corey Minyard [mailto:cminyard@xxxxxxxxxx] > Sent: Friday, August 12, 2016 10:56 PM > I'll try to test this, but I have one comment inline... Thank you very much! > On 08/11/2016 10:17 PM, Dave Young wrote: > > On 08/10/16 at 05:09pm, Hidehiro Kawai wrote: [snip] > >> diff --git a/arch/mips/kernel/crash.c b/arch/mips/kernel/crash.c > >> index 610f0f3..1723b17 100644 > >> --- a/arch/mips/kernel/crash.c > >> +++ b/arch/mips/kernel/crash.c > >> @@ -47,9 +47,14 @@ static void crash_shutdown_secondary(void *passed_regs) > >> > >> static void crash_kexec_prepare_cpus(void) > >> { > >> + static int cpus_stopped; > >> unsigned int msecs; > >> + unsigned int ncpus; > >> > >> - unsigned int ncpus = num_online_cpus() - 1;/* Excluding the panic cpu */ > >> + if (cpus_stopped) > >> + return; > > Wouldn't you want an atomic operation and some special handling here to > ensure that only one CPU does this? So if a CPU comes in here and > another CPU is already in the process stopping the CPUs it won't result in a > deadlock. Because this function can be called only one panicking CPU, there is no problem. There are two paths which crash_kexec_prepare_cpus is called. Path 1 (panic path): panic() crash_smp_send_stop() crash_kexec_prepare_cpus() Path 2 (oops path): crash_kexec() __crash_kexec() machine_crash_shutdown() default_machine_crash_shutdown() // for MIPS crash_kexec_prepare_cpus() Here, panic() and crash_kexec() run exclusively via panic_cpu atomic variable. So we can use cpus_stopped as normal variable. Best regards, Hidehiro Kawai
