Hi Will,

On Tue, Jan 10, 2017 at 11:32:48AM +0000, Will Deacon wrote:

On Wed, Dec 28, 2016 at 01:36:01PM +0900, AKASHI Takahiro wrote:

quoted

Primary kernel calls machine_crash_shutdown() to shut down non-boot cpus
and save registers' status in per-cpu ELF notes before starting crash
dump kernel. See kernel_kexec().
Even if not all secondary cpus have shut down, we do kdump anyway.

As we don't have to make non-boot(crashed) cpus offline (to preserve
correct status of cpus at crash dump) before shutting down, this patch
also adds a variant of smp_send_stop().

Signed-off-by: AKASHI Takahiro <redacted>
Reviewed-by: James Morse <james.morse@arm.com>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
---
 arch/arm64/include/asm/hardirq.h  |  2 +-
 arch/arm64/include/asm/kexec.h    | 42 +++++++++++++++++++++++++-
 arch/arm64/include/asm/smp.h      |  2 ++
 arch/arm64/kernel/machine_kexec.c | 56 ++++++++++++++++++++++++++++++++--
 arch/arm64/kernel/smp.c           | 63 +++++++++++++++++++++++++++++++++++++++
 5 files changed, 160 insertions(+), 5 deletions(-)

[...]

quoted

diff --git a/arch/arm64/include/asm/smp.h b/arch/arm64/include/asm/smp.h
index d050d720a1b4..cea009f2657d 100644
--- a/arch/arm64/include/asm/smp.h
+++ b/arch/arm64/include/asm/smp.h

@@ -148,6 +148,8 @@ static inline void cpu_panic_kernel(void)
  */
 bool cpus_are_stuck_in_kernel(void);
 
+extern void smp_send_crash_stop(void);
+
 #endif /* ifndef __ASSEMBLY__ */
 
 #endif /* ifndef __ASM_SMP_H */

diff --git a/arch/arm64/kernel/machine_kexec.c b/arch/arm64/kernel/machine_kexec.c
index bc96c8a7fc79..c60346d33bb1 100644
--- a/arch/arm64/kernel/machine_kexec.c
+++ b/arch/arm64/kernel/machine_kexec.c

@@ -9,6 +9,9 @@
  * published by the Free Software Foundation.
  */
 
+#include <linux/interrupt.h>
+#include <linux/irq.h>
+#include <linux/kernel.h>
 #include <linux/kexec.h>
 #include <linux/smp.h>
 

@@ -22,6 +25,7 @@
 extern const unsigned char arm64_relocate_new_kernel[];
 extern const unsigned long arm64_relocate_new_kernel_size;
 
+static bool in_crash_kexec;

Do you actually need this bool? Why not call kexec_crash_loaded() instead?

The two have different meanings:
"in_crash_kexec" indicates that kdump is taking place, while
kexec_crash_loaded() tells us only whether crash dump kernel has been
loaded or not.

It is crucial to distinguish them especially for machine_kexec()
which can be called on normal kexec even if kdump has been set up.

Thanks,
-Takahiro AKASHI

Will