* [PATCHv3] arm64:kexec: have own crash_smp_send_stop() for crash dump for nonpanic cores
@ 2017-08-17 2:24 Hoeun Ryu
2017-08-21 16:35 ` Catalin Marinas
0 siblings, 1 reply; 2+ messages in thread
From: Hoeun Ryu @ 2017-08-17 2:24 UTC (permalink / raw)
To: Catalin Marinas, Will Deacon, James Morse, Mark Rutland,
AKASHI Takahiro, Robin Murphy, Ard Biesheuvel, Ingo Molnar,
Peter Zijlstra (Intel),
Mark Salter, Suzuki K Poulose, David Daney, Rob Herring,
Dmitry Torokhov, Thomas Gleixner
Cc: Hoeun Ryu, linux-arm-kernel, linux-kernel
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(-)
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;
--
2.7.4
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCHv3] arm64:kexec: have own crash_smp_send_stop() for crash dump for nonpanic cores
2017-08-17 2:24 [PATCHv3] arm64:kexec: have own crash_smp_send_stop() for crash dump for nonpanic cores Hoeun Ryu
@ 2017-08-21 16:35 ` Catalin Marinas
0 siblings, 0 replies; 2+ messages in thread
From: Catalin Marinas @ 2017-08-21 16:35 UTC (permalink / raw)
To: Hoeun Ryu
Cc: Will Deacon, James Morse, Mark Rutland, AKASHI Takahiro,
Robin Murphy, Ard Biesheuvel, Ingo Molnar, Peter Zijlstra (Intel),
Mark Salter, Suzuki K Poulose, David Daney, Rob Herring,
Dmitry Torokhov, Thomas Gleixner, linux-kernel, linux-arm-kernel
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.
--
Catalin
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2017-08-17 2:24 [PATCHv3] arm64:kexec: have own crash_smp_send_stop() for crash dump for nonpanic cores Hoeun Ryu
2017-08-21 16:35 ` Catalin Marinas
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