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Subject[PATCHv3] arm64:kexec: have own crash_smp_send_stop() for crash dump for nonpanic cores
 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

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

crash_smp_send_stop() <= save crash dump for nonpanic cores

* crash_kexec_post_notifiers : true

crash_smp_send_stop() <= save crash dump for nonpanic cores
crash_smp_send_stop() <= just return.

Signed-off-by: Hoeun Ryu <>
Reviewed-by: James Morse <>
Tested-by: James Morse <>
- fix typos in the commit log.
- modify commit log about the result of this problem.
- add Tested-by/Reviewed-by: James Morse.
- 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(-)

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)

/* 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)

-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)

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