[PATCH V2 0/2] riscv: kexec: Fixup crash_save percpu and machine_kexec_mask_interrupts

[PATCH V2 0/2] riscv: kexec: Fixup crash_save percpu and machine_kexec_mask_interrupts

[guoren]

From: Guo Ren <guoren@linux.alibaba.com>

Current riscv kexec can't crash_save percpu states and disable
interrupts properly. The patch series fix them, make kexec work correct.

Changes in v2:
 - Add Fixes tags
 - Remove extern from bool smp_crash_stop_failed(void)

v1: https://lore.kernel.org/linux-riscv/20220816012701.561435-1-guoren@kernel.org/

Guo Ren (2):
  riscv: kexec: Disable all interrupts in kexec crash path
  riscv: kexec: Fixup crash_smp_send_stop with percpu crash_save_cpu

 arch/riscv/include/asm/smp.h      |  6 +++
 arch/riscv/kernel/machine_kexec.c | 44 +++++++++++----
 arch/riscv/kernel/smp.c           | 89 ++++++++++++++++++++++++++++++-
 3 files changed, 126 insertions(+), 13 deletions(-)

-- 
2.36.1


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[PATCH V2 1/2] riscv: kexec: Disable all interrupts in kexec crash path

[guoren]

From: Guo Ren <guoren@linux.alibaba.com>

If a crash happens on cpu3 and all interrupts are binding on cpu0, the
bad irq routing will cause a crash kernel which can't receive any irq.
Because crash kernel won't clean up all harts' PLIC enable bits in
enable registers. This patch is similar to 9141a003a491 ("ARM: 7316/1:
kexec: EOI active and mask all interrupts in kexec crash path") and
78fd584cdec0 ("arm64: kdump: implement machine_crash_shutdown()"), and
PowerPC also has the same mechanism.

Fixes: fba8a8674f68 ("RISC-V: Add kexec support")
Signed-off-by: Guo Ren <guoren@linux.alibaba.com>
Signed-off-by: Guo Ren <guoren@kernel.org>
Cc: Will Deacon <will.deacon@arm.com>
Cc: AKASHI Takahiro <takahiro.akashi@linaro.org>
Cc: Nick Kossifidis <mick@ics.forth.gr>
---
 arch/riscv/kernel/machine_kexec.c | 35 +++++++++++++++++++++++++++++++
 1 file changed, 35 insertions(+)

diff --git a/arch/riscv/kernel/machine_kexec.c b/arch/riscv/kernel/machine_kexec.c
index ee79e6839b86..db41c676e5a2 100644
--- a/arch/riscv/kernel/machine_kexec.c
+++ b/arch/riscv/kernel/machine_kexec.c
@@ -15,6 +15,8 @@
 #include <linux/compiler.h>	/* For unreachable() */
 #include <linux/cpu.h>		/* For cpu_down() */
 #include <linux/reboot.h>
+#include <linux/interrupt.h>
+#include <linux/irq.h>
 
 /*
  * kexec_image_info - Print received image details
@@ -154,6 +156,37 @@ void crash_smp_send_stop(void)
 	cpus_stopped = 1;
 }
 
+static void machine_kexec_mask_interrupts(void)
+{
+	unsigned int i;
+	struct irq_desc *desc;
+
+	for_each_irq_desc(i, desc) {
+		struct irq_chip *chip;
+		int ret;
+
+		chip = irq_desc_get_chip(desc);
+		if (!chip)
+			continue;
+
+		/*
+		 * First try to remove the active state. If this
+		 * fails, try to EOI the interrupt.
+		 */
+		ret = irq_set_irqchip_state(i, IRQCHIP_STATE_ACTIVE, false);
+
+		if (ret && irqd_irq_inprogress(&desc->irq_data) &&
+		    chip->irq_eoi)
+			chip->irq_eoi(&desc->irq_data);
+
+		if (chip->irq_mask)
+			chip->irq_mask(&desc->irq_data);
+
+		if (chip->irq_disable && !irqd_irq_disabled(&desc->irq_data))
+			chip->irq_disable(&desc->irq_data);
+	}
+}
+
 /*
  * machine_crash_shutdown - Prepare to kexec after a kernel crash
  *
@@ -169,6 +202,8 @@ machine_crash_shutdown(struct pt_regs *regs)
 	crash_smp_send_stop();
 
 	crash_save_cpu(regs, smp_processor_id());
+	machine_kexec_mask_interrupts();
+
 	pr_info("Starting crashdump kernel...\n");
 }
 
-- 
2.36.1


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[PATCH V2 2/2] riscv: kexec: Fixup crash_smp_send_stop with percpu crash_save_cpu

[guoren]

From: Guo Ren <guoren@linux.alibaba.com>

Current crash_smp_send_stop is the same as the generic one in
kernel/panic and misses crash_save_cpu in percpu. This patch is inspired
by 78fd584cdec0 ("arm64: kdump: implement machine_crash_shutdown()")
and adds the same mechanism for riscv.

Fixes: ad943893d5f1 ("RISC-V: Fixup schedule out issue in machine_crash_shutdown()")
Signed-off-by: Guo Ren <guoren@linux.alibaba.com>
Signed-off-by: Guo Ren <guoren@kernel.org>
Cc: AKASHI Takahiro <takahiro.akashi@linaro.org>
---
 arch/riscv/include/asm/smp.h      |  6 +++
 arch/riscv/kernel/machine_kexec.c | 19 ++-----
 arch/riscv/kernel/smp.c           | 89 ++++++++++++++++++++++++++++++-
 3 files changed, 96 insertions(+), 18 deletions(-)

diff --git a/arch/riscv/include/asm/smp.h b/arch/riscv/include/asm/smp.h
index d3443be7eedc..8b40e15bea36 100644
--- a/arch/riscv/include/asm/smp.h
+++ b/arch/riscv/include/asm/smp.h
@@ -50,6 +50,12 @@ void riscv_set_ipi_ops(const struct riscv_ipi_ops *ops);
 /* Clear IPI for current CPU */
 void riscv_clear_ipi(void);
 
+/* stop and save status for other CPUs */
+void crash_smp_send_stop(void);
+
+/* Check other CPUs stop or not */
+bool smp_crash_stop_failed(void);
+
 /* Secondary hart entry */
 asmlinkage void smp_callin(void);
 
diff --git a/arch/riscv/kernel/machine_kexec.c b/arch/riscv/kernel/machine_kexec.c
index db41c676e5a2..34c86d337448 100644
--- a/arch/riscv/kernel/machine_kexec.c
+++ b/arch/riscv/kernel/machine_kexec.c
@@ -140,22 +140,6 @@ void machine_shutdown(void)
 #endif
 }
 
-/* Override the weak function in kernel/panic.c */
-void crash_smp_send_stop(void)
-{
-	static int cpus_stopped;
-
-	/*
-	 * This function can be called twice in panic path, but obviously
-	 * we execute this only once.
-	 */
-	if (cpus_stopped)
-		return;
-
-	smp_send_stop();
-	cpus_stopped = 1;
-}
-
 static void machine_kexec_mask_interrupts(void)
 {
 	unsigned int i;
@@ -230,6 +214,9 @@ machine_kexec(struct kimage *image)
 	void *control_code_buffer = page_address(image->control_code_page);
 	riscv_kexec_method kexec_method = NULL;
 
+	WARN(smp_crash_stop_failed(),
+		"Some CPUs may be stale, kdump will be unreliable.\n");
+
 	if (image->type != KEXEC_TYPE_CRASH)
 		kexec_method = control_code_buffer;
 	else
diff --git a/arch/riscv/kernel/smp.c b/arch/riscv/kernel/smp.c
index 760a64518c58..a75ad9c373cd 100644
--- a/arch/riscv/kernel/smp.c
+++ b/arch/riscv/kernel/smp.c
@@ -12,6 +12,7 @@
 #include <linux/clockchips.h>
 #include <linux/interrupt.h>
 #include <linux/module.h>
+#include <linux/kexec.h>
 #include <linux/profile.h>
 #include <linux/smp.h>
 #include <linux/sched.h>
@@ -27,6 +28,7 @@ enum ipi_message_type {
 	IPI_RESCHEDULE,
 	IPI_CALL_FUNC,
 	IPI_CPU_STOP,
+	IPI_CPU_CRASH_STOP,
 	IPI_IRQ_WORK,
 	IPI_TIMER,
 	IPI_MAX
@@ -71,6 +73,22 @@ static void ipi_stop(void)
 		wait_for_interrupt();
 }
 
+#ifdef CONFIG_KEXEC_CORE
+static atomic_t waiting_for_crash_ipi = ATOMIC_INIT(0);
+
+static void ipi_cpu_crash_stop(unsigned int cpu, struct pt_regs *regs)
+{
+	crash_save_cpu(regs, cpu);
+
+	atomic_dec(&waiting_for_crash_ipi);
+
+	local_irq_disable();
+
+	while(1)
+		wait_for_interrupt();
+}
+#endif
+
 static const struct riscv_ipi_ops *ipi_ops __ro_after_init;
 
 void riscv_set_ipi_ops(const struct riscv_ipi_ops *ops)
@@ -124,8 +142,9 @@ void arch_irq_work_raise(void)
 
 void handle_IPI(struct pt_regs *regs)
 {
-	unsigned long *pending_ipis = &ipi_data[smp_processor_id()].bits;
-	unsigned long *stats = ipi_data[smp_processor_id()].stats;
+	unsigned int cpu = smp_processor_id();
+	unsigned long *pending_ipis = &ipi_data[cpu].bits;
+	unsigned long *stats = ipi_data[cpu].stats;
 
 	riscv_clear_ipi();
 
@@ -154,6 +173,13 @@ void handle_IPI(struct pt_regs *regs)
 			ipi_stop();
 		}
 
+		if (ops & (1 << IPI_CPU_CRASH_STOP)) {
+#ifdef CONFIG_KEXEC_CORE
+			ipi_cpu_crash_stop(cpu, get_irq_regs());
+#endif
+			unreachable();
+		}
+
 		if (ops & (1 << IPI_IRQ_WORK)) {
 			stats[IPI_IRQ_WORK]++;
 			irq_work_run();
@@ -176,6 +202,7 @@ static const char * const ipi_names[] = {
 	[IPI_RESCHEDULE]	= "Rescheduling interrupts",
 	[IPI_CALL_FUNC]		= "Function call interrupts",
 	[IPI_CPU_STOP]		= "CPU stop interrupts",
+	[IPI_CPU_CRASH_STOP]	= "CPU stop (for crash dump) interrupts",
 	[IPI_IRQ_WORK]		= "IRQ work interrupts",
 	[IPI_TIMER]		= "Timer broadcast interrupts",
 };
@@ -235,6 +262,64 @@ void smp_send_stop(void)
 			   cpumask_pr_args(cpu_online_mask));
 }
 
+#ifdef CONFIG_KEXEC_CORE
+/*
+ * The number of CPUs online, not counting this CPU (which may not be
+ * fully online and so not counted in num_online_cpus()).
+ */
+static inline unsigned int num_other_online_cpus(void)
+{
+	unsigned int this_cpu_online = cpu_online(smp_processor_id());
+
+	return num_online_cpus() - this_cpu_online;
+}
+
+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 this cpu is the only one alive at this point in time, online or
+	 * not, there are no stop messages to be sent around, so just back out.
+	 */
+	if (num_other_online_cpus() == 0)
+		return;
+
+	cpumask_copy(&mask, cpu_online_mask);
+	cpumask_clear_cpu(smp_processor_id(), &mask);
+
+	atomic_set(&waiting_for_crash_ipi, num_other_online_cpus());
+
+	pr_crit("SMP: stopping secondary CPUs\n");
+	send_ipi_mask(&mask, IPI_CPU_CRASH_STOP);
+
+	/* Wait up to one second for other CPUs to stop */
+	timeout = USEC_PER_SEC;
+	while ((atomic_read(&waiting_for_crash_ipi) > 0) && timeout--)
+		udelay(1);
+
+	if (atomic_read(&waiting_for_crash_ipi) > 0)
+		pr_warn("SMP: failed to stop secondary CPUs %*pbl\n",
+			cpumask_pr_args(&mask));
+}
+
+bool smp_crash_stop_failed(void)
+{
+	return (atomic_read(&waiting_for_crash_ipi) > 0);
+}
+#endif
+
 void smp_send_reschedule(int cpu)
 {
 	send_ipi_single(cpu, IPI_RESCHEDULE);
-- 
2.36.1


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Re: [PATCH V2 1/2] riscv: kexec: Disable all interrupts in kexec crash path

[Xianting Tian]

It is ok for me

Reviewed-by: Xianting Tian <xianting.tian@linux.alibaba.com>

在 2022/8/18 上午12:12, guoren@kernel.org 写道:
> From: Guo Ren <guoren@linux.alibaba.com>
>
> If a crash happens on cpu3 and all interrupts are binding on cpu0, the
> bad irq routing will cause a crash kernel which can't receive any irq.
> Because crash kernel won't clean up all harts' PLIC enable bits in
> enable registers. This patch is similar to 9141a003a491 ("ARM: 7316/1:
> kexec: EOI active and mask all interrupts in kexec crash path") and
> 78fd584cdec0 ("arm64: kdump: implement machine_crash_shutdown()"), and
> PowerPC also has the same mechanism.
>
> Fixes: fba8a8674f68 ("RISC-V: Add kexec support")
> Signed-off-by: Guo Ren <guoren@linux.alibaba.com>
> Signed-off-by: Guo Ren <guoren@kernel.org>
> Cc: Will Deacon <will.deacon@arm.com>
> Cc: AKASHI Takahiro <takahiro.akashi@linaro.org>
> Cc: Nick Kossifidis <mick@ics.forth.gr>
> ---
>   arch/riscv/kernel/machine_kexec.c | 35 +++++++++++++++++++++++++++++++
>   1 file changed, 35 insertions(+)
>
> diff --git a/arch/riscv/kernel/machine_kexec.c b/arch/riscv/kernel/machine_kexec.c
> index ee79e6839b86..db41c676e5a2 100644
> --- a/arch/riscv/kernel/machine_kexec.c
> +++ b/arch/riscv/kernel/machine_kexec.c
> @@ -15,6 +15,8 @@
>   #include <linux/compiler.h>	/* For unreachable() */
>   #include <linux/cpu.h>		/* For cpu_down() */
>   #include <linux/reboot.h>
> +#include <linux/interrupt.h>
> +#include <linux/irq.h>
>   
>   /*
>    * kexec_image_info - Print received image details
> @@ -154,6 +156,37 @@ void crash_smp_send_stop(void)
>   	cpus_stopped = 1;
>   }
>   
> +static void machine_kexec_mask_interrupts(void)
> +{
> +	unsigned int i;
> +	struct irq_desc *desc;
> +
> +	for_each_irq_desc(i, desc) {
> +		struct irq_chip *chip;
> +		int ret;
> +
> +		chip = irq_desc_get_chip(desc);
> +		if (!chip)
> +			continue;
> +
> +		/*
> +		 * First try to remove the active state. If this
> +		 * fails, try to EOI the interrupt.
> +		 */
> +		ret = irq_set_irqchip_state(i, IRQCHIP_STATE_ACTIVE, false);
> +
> +		if (ret && irqd_irq_inprogress(&desc->irq_data) &&
> +		    chip->irq_eoi)
> +			chip->irq_eoi(&desc->irq_data);
> +
> +		if (chip->irq_mask)
> +			chip->irq_mask(&desc->irq_data);
> +
> +		if (chip->irq_disable && !irqd_irq_disabled(&desc->irq_data))
> +			chip->irq_disable(&desc->irq_data);
> +	}
> +}
> +
>   /*
>    * machine_crash_shutdown - Prepare to kexec after a kernel crash
>    *
> @@ -169,6 +202,8 @@ machine_crash_shutdown(struct pt_regs *regs)
>   	crash_smp_send_stop();
>   
>   	crash_save_cpu(regs, smp_processor_id());
> +	machine_kexec_mask_interrupts();
> +
>   	pr_info("Starting crashdump kernel...\n");
>   }
>   

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Re: [PATCH V2 2/2] riscv: kexec: Fixup crash_smp_send_stop with percpu crash_save_cpu

[Xianting Tian]

It is ok for me

Reviewed-by: Xianting Tian <xianting.tian@linux.alibaba.com>

在 2022/8/18 上午12:12, guoren@kernel.org 写道:
> From: Guo Ren <guoren@linux.alibaba.com>
>
> Current crash_smp_send_stop is the same as the generic one in
> kernel/panic and misses crash_save_cpu in percpu. This patch is inspired
> by 78fd584cdec0 ("arm64: kdump: implement machine_crash_shutdown()")
> and adds the same mechanism for riscv.
>
> Fixes: ad943893d5f1 ("RISC-V: Fixup schedule out issue in machine_crash_shutdown()")
> Signed-off-by: Guo Ren <guoren@linux.alibaba.com>
> Signed-off-by: Guo Ren <guoren@kernel.org>
> Cc: AKASHI Takahiro <takahiro.akashi@linaro.org>
> ---
>   arch/riscv/include/asm/smp.h      |  6 +++
>   arch/riscv/kernel/machine_kexec.c | 19 ++-----
>   arch/riscv/kernel/smp.c           | 89 ++++++++++++++++++++++++++++++-
>   3 files changed, 96 insertions(+), 18 deletions(-)
>
> diff --git a/arch/riscv/include/asm/smp.h b/arch/riscv/include/asm/smp.h
> index d3443be7eedc..8b40e15bea36 100644
> --- a/arch/riscv/include/asm/smp.h
> +++ b/arch/riscv/include/asm/smp.h
> @@ -50,6 +50,12 @@ void riscv_set_ipi_ops(const struct riscv_ipi_ops *ops);
>   /* Clear IPI for current CPU */
>   void riscv_clear_ipi(void);
>   
> +/* stop and save status for other CPUs */
> +void crash_smp_send_stop(void);
> +
> +/* Check other CPUs stop or not */
> +bool smp_crash_stop_failed(void);
> +
>   /* Secondary hart entry */
>   asmlinkage void smp_callin(void);
>   
> diff --git a/arch/riscv/kernel/machine_kexec.c b/arch/riscv/kernel/machine_kexec.c
> index db41c676e5a2..34c86d337448 100644
> --- a/arch/riscv/kernel/machine_kexec.c
> +++ b/arch/riscv/kernel/machine_kexec.c
> @@ -140,22 +140,6 @@ void machine_shutdown(void)
>   #endif
>   }
>   
> -/* Override the weak function in kernel/panic.c */
> -void crash_smp_send_stop(void)
> -{
> -	static int cpus_stopped;
> -
> -	/*
> -	 * This function can be called twice in panic path, but obviously
> -	 * we execute this only once.
> -	 */
> -	if (cpus_stopped)
> -		return;
> -
> -	smp_send_stop();
> -	cpus_stopped = 1;
> -}
> -
>   static void machine_kexec_mask_interrupts(void)
>   {
>   	unsigned int i;
> @@ -230,6 +214,9 @@ machine_kexec(struct kimage *image)
>   	void *control_code_buffer = page_address(image->control_code_page);
>   	riscv_kexec_method kexec_method = NULL;
>   
> +	WARN(smp_crash_stop_failed(),
> +		"Some CPUs may be stale, kdump will be unreliable.\n");
> +
>   	if (image->type != KEXEC_TYPE_CRASH)
>   		kexec_method = control_code_buffer;
>   	else
> diff --git a/arch/riscv/kernel/smp.c b/arch/riscv/kernel/smp.c
> index 760a64518c58..a75ad9c373cd 100644
> --- a/arch/riscv/kernel/smp.c
> +++ b/arch/riscv/kernel/smp.c
> @@ -12,6 +12,7 @@
>   #include <linux/clockchips.h>
>   #include <linux/interrupt.h>
>   #include <linux/module.h>
> +#include <linux/kexec.h>
>   #include <linux/profile.h>
>   #include <linux/smp.h>
>   #include <linux/sched.h>
> @@ -27,6 +28,7 @@ enum ipi_message_type {
>   	IPI_RESCHEDULE,
>   	IPI_CALL_FUNC,
>   	IPI_CPU_STOP,
> +	IPI_CPU_CRASH_STOP,
>   	IPI_IRQ_WORK,
>   	IPI_TIMER,
>   	IPI_MAX
> @@ -71,6 +73,22 @@ static void ipi_stop(void)
>   		wait_for_interrupt();
>   }
>   
> +#ifdef CONFIG_KEXEC_CORE
> +static atomic_t waiting_for_crash_ipi = ATOMIC_INIT(0);
> +
> +static void ipi_cpu_crash_stop(unsigned int cpu, struct pt_regs *regs)
> +{
> +	crash_save_cpu(regs, cpu);
> +
> +	atomic_dec(&waiting_for_crash_ipi);
> +
> +	local_irq_disable();
> +
> +	while(1)
> +		wait_for_interrupt();
> +}
> +#endif
> +
>   static const struct riscv_ipi_ops *ipi_ops __ro_after_init;
>   
>   void riscv_set_ipi_ops(const struct riscv_ipi_ops *ops)
> @@ -124,8 +142,9 @@ void arch_irq_work_raise(void)
>   
>   void handle_IPI(struct pt_regs *regs)
>   {
> -	unsigned long *pending_ipis = &ipi_data[smp_processor_id()].bits;
> -	unsigned long *stats = ipi_data[smp_processor_id()].stats;
> +	unsigned int cpu = smp_processor_id();
> +	unsigned long *pending_ipis = &ipi_data[cpu].bits;
> +	unsigned long *stats = ipi_data[cpu].stats;
>   
>   	riscv_clear_ipi();
>   
> @@ -154,6 +173,13 @@ void handle_IPI(struct pt_regs *regs)
>   			ipi_stop();
>   		}
>   
> +		if (ops & (1 << IPI_CPU_CRASH_STOP)) {
> +#ifdef CONFIG_KEXEC_CORE
> +			ipi_cpu_crash_stop(cpu, get_irq_regs());
> +#endif
> +			unreachable();
> +		}
> +
>   		if (ops & (1 << IPI_IRQ_WORK)) {
>   			stats[IPI_IRQ_WORK]++;
>   			irq_work_run();
> @@ -176,6 +202,7 @@ static const char * const ipi_names[] = {
>   	[IPI_RESCHEDULE]	= "Rescheduling interrupts",
>   	[IPI_CALL_FUNC]		= "Function call interrupts",
>   	[IPI_CPU_STOP]		= "CPU stop interrupts",
> +	[IPI_CPU_CRASH_STOP]	= "CPU stop (for crash dump) interrupts",
>   	[IPI_IRQ_WORK]		= "IRQ work interrupts",
>   	[IPI_TIMER]		= "Timer broadcast interrupts",
>   };
> @@ -235,6 +262,64 @@ void smp_send_stop(void)
>   			   cpumask_pr_args(cpu_online_mask));
>   }
>   
> +#ifdef CONFIG_KEXEC_CORE
> +/*
> + * The number of CPUs online, not counting this CPU (which may not be
> + * fully online and so not counted in num_online_cpus()).
> + */
> +static inline unsigned int num_other_online_cpus(void)
> +{
> +	unsigned int this_cpu_online = cpu_online(smp_processor_id());
> +
> +	return num_online_cpus() - this_cpu_online;
> +}
> +
> +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 this cpu is the only one alive at this point in time, online or
> +	 * not, there are no stop messages to be sent around, so just back out.
> +	 */
> +	if (num_other_online_cpus() == 0)
> +		return;
> +
> +	cpumask_copy(&mask, cpu_online_mask);
> +	cpumask_clear_cpu(smp_processor_id(), &mask);
> +
> +	atomic_set(&waiting_for_crash_ipi, num_other_online_cpus());
> +
> +	pr_crit("SMP: stopping secondary CPUs\n");
> +	send_ipi_mask(&mask, IPI_CPU_CRASH_STOP);
> +
> +	/* Wait up to one second for other CPUs to stop */
> +	timeout = USEC_PER_SEC;
> +	while ((atomic_read(&waiting_for_crash_ipi) > 0) && timeout--)
> +		udelay(1);
> +
> +	if (atomic_read(&waiting_for_crash_ipi) > 0)
> +		pr_warn("SMP: failed to stop secondary CPUs %*pbl\n",
> +			cpumask_pr_args(&mask));
> +}
> +
> +bool smp_crash_stop_failed(void)
> +{
> +	return (atomic_read(&waiting_for_crash_ipi) > 0);
> +}
> +#endif
> +
>   void smp_send_reschedule(int cpu)
>   {
>   	send_ipi_single(cpu, IPI_RESCHEDULE);

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