| Message ID | 1502936722-549-1-git-send-email-hoeun.ryu@gmail.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Thu, Aug 17, 2017 at 11:24:27AM +0900, Hoeun Ryu wrote: > Commit 0ee5941 : (x86/panic: replace smp_send_stop() with kdump friendly > version in panic path) introduced crash_smp_send_stop() which is a weak > function and can be overridden by architecture codes to fix the side effect > caused by commit f06e515 : (kernel/panic.c: add "crash_kexec_post_ > notifiers" option). > > ARM64 architecture uses the weak version function and the problem is that > the weak function simply calls smp_send_stop() which makes other CPUs > offline and takes away the chance to save crash information for nonpanic > CPUs in machine_crash_shutdown() when crash_kexec_post_notifiers kernel > option is enabled. > > Calling smp_send_crash_stop() in machine_crash_shutdown() is useless > because all nonpanic CPUs are already offline by smp_send_stop() in this > case and smp_send_crash_stop() only works against online CPUs. > > The result is that secondary CPUs registers are not saved by > crash_save_cpu() and the vmcore file misreports these CPUs as being > offline. > > crash_smp_send_stop() is implemented to fix this problem by replacing the > existing smp_send_crash_stop() and adding a check for multiple calling to > the function. The function (strong symbol version) saves crash information > for nonpanic CPUs and machine_crash_shutdown() tries to save crash > information for nonpanic CPUs only when crash_kexec_post_notifiers kernel > option is disabled. > > * crash_kexec_post_notifiers : false > > panic() > __crash_kexec() > machine_crash_shutdown() > crash_smp_send_stop() <= save crash dump for nonpanic cores > > * crash_kexec_post_notifiers : true > > panic() > crash_smp_send_stop() <= save crash dump for nonpanic cores > __crash_kexec() > machine_crash_shutdown() > crash_smp_send_stop() <= just return. > > Signed-off-by: Hoeun Ryu <hoeun.ryu@gmail.com> > Reviewed-by: James Morse <james.morse@arm.com> > Tested-by: James Morse <james.morse@arm.com> Queued for 4.14. Thanks.
diff --git a/arch/arm64/include/asm/smp.h b/arch/arm64/include/asm/smp.h index 55f08c5..f82b447 100644 --- a/arch/arm64/include/asm/smp.h +++ b/arch/arm64/include/asm/smp.h @@ -148,7 +148,7 @@ static inline void cpu_panic_kernel(void) */ bool cpus_are_stuck_in_kernel(void); -extern void smp_send_crash_stop(void); +extern void crash_smp_send_stop(void); extern bool smp_crash_stop_failed(void); #endif /* ifndef __ASSEMBLY__ */ diff --git a/arch/arm64/kernel/machine_kexec.c b/arch/arm64/kernel/machine_kexec.c index 481f54a..11121f6 100644 --- a/arch/arm64/kernel/machine_kexec.c +++ b/arch/arm64/kernel/machine_kexec.c @@ -252,7 +252,7 @@ void machine_crash_shutdown(struct pt_regs *regs) local_irq_disable(); /* shutdown non-crashing cpus */ - smp_send_crash_stop(); + crash_smp_send_stop(); /* for crashing cpu */ crash_save_cpu(regs, smp_processor_id()); diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c index dc66e6e..73d8f5e 100644 --- a/arch/arm64/kernel/smp.c +++ b/arch/arm64/kernel/smp.c @@ -977,11 +977,21 @@ void smp_send_stop(void) } #ifdef CONFIG_KEXEC_CORE -void smp_send_crash_stop(void) +void crash_smp_send_stop(void) { + static int cpus_stopped; cpumask_t mask; unsigned long timeout; + /* + * This function can be called twice in panic path, but obviously + * we execute this only once. + */ + if (cpus_stopped) + return; + + cpus_stopped = 1; + if (num_online_cpus() == 1) return;
Commit 0ee5941 : (x86/panic: replace smp_send_stop() with kdump friendly version in panic path) introduced crash_smp_send_stop() which is a weak function and can be overridden by architecture codes to fix the side effect caused by commit f06e515 : (kernel/panic.c: add "crash_kexec_post_ notifiers" option). ARM64 architecture uses the weak version function and the problem is that the weak function simply calls smp_send_stop() which makes other CPUs offline and takes away the chance to save crash information for nonpanic CPUs in machine_crash_shutdown() when crash_kexec_post_notifiers kernel option is enabled. Calling smp_send_crash_stop() in machine_crash_shutdown() is useless because all nonpanic CPUs are already offline by smp_send_stop() in this case and smp_send_crash_stop() only works against online CPUs. The result is that secondary CPUs registers are not saved by crash_save_cpu() and the vmcore file misreports these CPUs as being offline. crash_smp_send_stop() is implemented to fix this problem by replacing the existing smp_send_crash_stop() and adding a check for multiple calling to the function. The function (strong symbol version) saves crash information for nonpanic CPUs and machine_crash_shutdown() tries to save crash information for nonpanic CPUs only when crash_kexec_post_notifiers kernel option is disabled. * crash_kexec_post_notifiers : false panic() __crash_kexec() machine_crash_shutdown() crash_smp_send_stop() <= save crash dump for nonpanic cores * crash_kexec_post_notifiers : true panic() crash_smp_send_stop() <= save crash dump for nonpanic cores __crash_kexec() machine_crash_shutdown() crash_smp_send_stop() <= just return. Signed-off-by: Hoeun Ryu <hoeun.ryu@gmail.com> Reviewed-by: James Morse <james.morse@arm.com> Tested-by: James Morse <james.morse@arm.com> --- v3: - fix typos in the commit log. - modify commit log about the result of this problem. - add Tested-by/Reviewed-by: James Morse. v2: - replace the existing smp_send_crash_stop() with crash_smp_send_stop() and adding called-twice logic to it. - modify the commit message. arch/arm64/include/asm/smp.h | 2 +- arch/arm64/kernel/machine_kexec.c | 2 +- arch/arm64/kernel/smp.c | 12 +++++++++++- 3 files changed, 13 insertions(+), 3 deletions(-)