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 overriden by architecture codes to fix the side effect
caused by commit f06e515 : (kernel/panic.c: add "crash_kexec_post_
notifiers" option).
ARM 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_call_function(machine_crash_nonpanic_core, NULL, false) in
the function is useless because all nonpanic CPUs are already offline by
smp_send_stop() in this case and smp_call_function() only works against
online CPUs.
The result is that /proc/vmcore is not available with the error messages;
"Warning: Zero PT_NOTE entries found", "Kdump: vmcore not initialized".
crash_smp_send_stop() is implemented for ARM architecture to fix this
problem and the function (strong symbol version) saves crash information
for nonpanic CPUs using smp_call_function() and machine_crash_shutdown()
tries to save crash information for nonpanic CPUs only when
crash_kexec_post_notifiers kernel option is disabled.
We might be able to implement the function like arm64 or x86 using a
dedicated IPI (let's say IPI_CPU_CRASH_STOP), but we cannot implement this
function like that because of the lack of IPI slots. Please see the commit
e7273ff4 : (ARM: 8488/1: Make IPI_CPU_BACKTRACE a "non-secure" SGI)
Signed-off-by: Hoeun Ryu <[email protected]>
---
v3:
- remove 'WARN_ON(num_online_cpus() > 1)' in machine_crash_shutdown().
it's a false check for the case when crash_kexec_post_notifiers
kernel option is disabled.
v2:
- calling crash_smp_send_stop() in machine_crash_shutdown() for the case
when crash_kexec_post_notifiers kernel option is disabled.
- fix commit messages for it.
arch/arm/kernel/machine_kexec.c | 40 +++++++++++++++++++++++++++++-----------
1 file changed, 29 insertions(+), 11 deletions(-)
diff --git a/arch/arm/kernel/machine_kexec.c b/arch/arm/kernel/machine_kexec.c
index fe1419e..82ef7c7 100644
--- a/arch/arm/kernel/machine_kexec.c
+++ b/arch/arm/kernel/machine_kexec.c
@@ -94,6 +94,34 @@ void machine_crash_nonpanic_core(void *unused)
cpu_relax();
}
+void crash_smp_send_stop(void)
+{
+ static int cpus_stopped;
+ unsigned long msecs;
+
+ /*
+ * 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;
+
+ atomic_set(&waiting_for_crash_ipi, num_online_cpus() - 1);
+ smp_call_function(machine_crash_nonpanic_core, NULL, false);
+ msecs = 1000; /* Wait at most a second for the other cpus to stop */
+ while ((atomic_read(&waiting_for_crash_ipi) > 0) && msecs) {
+ mdelay(1);
+ msecs--;
+ }
+ if (atomic_read(&waiting_for_crash_ipi) > 0)
+ pr_warn("Non-crashing CPUs did not react to IPI\n");
+}
+
static void machine_kexec_mask_interrupts(void)
{
unsigned int i;
@@ -119,19 +147,9 @@ static void machine_kexec_mask_interrupts(void)
void machine_crash_shutdown(struct pt_regs *regs)
{
- unsigned long msecs;
-
local_irq_disable();
- atomic_set(&waiting_for_crash_ipi, num_online_cpus() - 1);
- smp_call_function(machine_crash_nonpanic_core, NULL, false);
- msecs = 1000; /* Wait at most a second for the other cpus to stop */
- while ((atomic_read(&waiting_for_crash_ipi) > 0) && msecs) {
- mdelay(1);
- msecs--;
- }
- if (atomic_read(&waiting_for_crash_ipi) > 0)
- pr_warn("Non-crashing CPUs did not react to IPI\n");
+ crash_smp_send_stop();
crash_save_cpu(regs, smp_processor_id());
machine_kexec_mask_interrupts();
--
2.7.4
Hello, All.
Would you please review this patch ?
I haven't had any respond to this patch.
Thank you.
On Tue, 2017-08-08 at 10:22 +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 overriden by architecture codes to fix the side effect
> caused by commit f06e515 : (kernel/panic.c: add "crash_kexec_post_
> notifiers" option).
>
> ARM 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_call_function(machine_crash_nonpanic_core, NULL, false) in
> the function is useless because all nonpanic CPUs are already offline by
> smp_send_stop() in this case and smp_call_function() only works against
> online CPUs.
>
> The result is that /proc/vmcore is not available with the error messages;
> "Warning: Zero PT_NOTE entries found", "Kdump: vmcore not initialized".
>
> crash_smp_send_stop() is implemented for ARM architecture to fix this
> problem and the function (strong symbol version) saves crash information
> for nonpanic CPUs using smp_call_function() and machine_crash_shutdown()
> tries to save crash information for nonpanic CPUs only when
> crash_kexec_post_notifiers kernel option is disabled.
>
> We might be able to implement the function like arm64 or x86 using a
> dedicated IPI (let's say IPI_CPU_CRASH_STOP), but we cannot implement this
> function like that because of the lack of IPI slots. Please see the commit
> e7273ff4 : (ARM: 8488/1: Make IPI_CPU_BACKTRACE a "non-secure" SGI)
>
> Signed-off-by: Hoeun Ryu <[email protected]>
> ---
> v3:
> - remove 'WARN_ON(num_online_cpus() > 1)' in machine_crash_shutdown().
> it's a false check for the case when crash_kexec_post_notifiers
> kernel option is disabled.
> v2:
> - calling crash_smp_send_stop() in machine_crash_shutdown() for the case
> when crash_kexec_post_notifiers kernel option is disabled.
> - fix commit messages for it.
>
> arch/arm/kernel/machine_kexec.c | 40 +++++++++++++++++++++++++++++-----------
> 1 file changed, 29 insertions(+), 11 deletions(-)
>
> diff --git a/arch/arm/kernel/machine_kexec.c b/arch/arm/kernel/machine_kexec.c
> index fe1419e..82ef7c7 100644
> --- a/arch/arm/kernel/machine_kexec.c
> +++ b/arch/arm/kernel/machine_kexec.c
> @@ -94,6 +94,34 @@ void machine_crash_nonpanic_core(void *unused)
> cpu_relax();
> }
>
> +void crash_smp_send_stop(void)
> +{
> + static int cpus_stopped;
> + unsigned long msecs;
> +
> + /*
> + * 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;
> +
> + atomic_set(&waiting_for_crash_ipi, num_online_cpus() - 1);
> + smp_call_function(machine_crash_nonpanic_core, NULL, false);
> + msecs = 1000; /* Wait at most a second for the other cpus to stop */
> + while ((atomic_read(&waiting_for_crash_ipi) > 0) && msecs) {
> + mdelay(1);
> + msecs--;
> + }
> + if (atomic_read(&waiting_for_crash_ipi) > 0)
> + pr_warn("Non-crashing CPUs did not react to IPI\n");
> +}
> +
> static void machine_kexec_mask_interrupts(void)
> {
> unsigned int i;
> @@ -119,19 +147,9 @@ static void machine_kexec_mask_interrupts(void)
>
> void machine_crash_shutdown(struct pt_regs *regs)
> {
> - unsigned long msecs;
> -
> local_irq_disable();
>
> - atomic_set(&waiting_for_crash_ipi, num_online_cpus() - 1);
> - smp_call_function(machine_crash_nonpanic_core, NULL, false);
> - msecs = 1000; /* Wait at most a second for the other cpus to stop */
> - while ((atomic_read(&waiting_for_crash_ipi) > 0) && msecs) {
> - mdelay(1);
> - msecs--;
> - }
> - if (atomic_read(&waiting_for_crash_ipi) > 0)
> - pr_warn("Non-crashing CPUs did not react to IPI\n");
> + crash_smp_send_stop();
>
> crash_save_cpu(regs, smp_processor_id());
> machine_kexec_mask_interrupts();