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Commit d44e2ad7 authored by Rohit Vaswani's avatar Rohit Vaswani Committed by Matt Wagantall
Browse files

ARM64: smp: implement arch_trigger_all_cpus_backtrace using IPI 



Since ARM64 doesn't have an NMI, send an IPI to all other CPUs
(current cpu prints the stack directly) to capture a backtrace.

Change-Id: Ib90494123205b3bbaa0b244ccde6c7e40a560199
Signed-off-by: default avatarRohit Vaswani <rvaswani@codeaurora.org>
[abhimany: fixup the nmi header to account for arm64]
Signed-off-by: default avatarAbhimanyu Kapur <abhimany@codeaurora.org>
parent b3385bd8

arch/arm64/include/asm/hardirq.h

+1 −1
Original line number Diff line number Diff line
@@ -20,7 +20,7 @@ 
#include <linux/threads.h>

#include <asm/irq.h>



#define NR_IPI	7

#define NR_IPI	8



typedef struct {

	unsigned int __softirq_pending;

arch/arm64/include/asm/irq.h

+3 −0
Original line number Diff line number Diff line
@@ -7,4 +7,7 @@ extern void (*handle_arch_irq)(struct pt_regs *); 
extern void migrate_irqs(void);

extern void set_handle_irq(void (*handle_irq)(struct pt_regs *));



void arch_trigger_all_cpu_backtrace(void);

#define arch_trigger_all_cpu_backtrace arch_trigger_all_cpu_backtrace



#endif

arch/arm64/kernel/smp.c

+71 −0
Original line number Diff line number Diff line
@@ -70,6 +70,7 @@ enum ipi_msg_type { 
	IPI_TIMER,

	IPI_IRQ_WORK,

	IPI_WAKEUP,

	IPI_CPU_BACKTRACE,

};



/*
@@ -497,6 +498,7 @@ static const char *ipi_types[NR_IPI] __tracepoint_string = { 
	S(IPI_TIMER, "Timer broadcast interrupts"),

	S(IPI_IRQ_WORK, "IRQ work interrupts"),

	S(IPI_WAKEUP, "CPU wakeup interrupts"),

	S(IPI_CPU_BACKTRACE, "CPU backtrace"),

};



static void smp_cross_call(const struct cpumask *target, unsigned int ipinr)
@@ -581,6 +583,72 @@ static void ipi_cpu_stop(unsigned int cpu, struct pt_regs *regs) 
		cpu_relax();

}



static cpumask_t backtrace_mask;

static DEFINE_RAW_SPINLOCK(backtrace_lock);



/* "in progress" flag of arch_trigger_all_cpu_backtrace */

static unsigned long backtrace_flag;



static void smp_send_all_cpu_backtrace(void)

{

	unsigned int this_cpu = smp_processor_id();

	int i;



	if (test_and_set_bit(0, &backtrace_flag))

		/*

		 * If there is already a trigger_all_cpu_backtrace() in progress

		 * (backtrace_flag == 1), don't output double cpu dump infos.

		 */

		return;



	cpumask_copy(&backtrace_mask, cpu_online_mask);

	cpu_clear(this_cpu, backtrace_mask);



	pr_info("Backtrace for cpu %d (current):\n", this_cpu);

	dump_stack();



	pr_info("\nsending IPI to all other CPUs:\n");

	if (!cpus_empty(backtrace_mask))

		smp_cross_call(&backtrace_mask, IPI_CPU_BACKTRACE);



	/* Wait for up to 10 seconds for all other CPUs to do the backtrace */

	for (i = 0; i < 10 * 1000; i++) {

		if (cpumask_empty(&backtrace_mask))

			break;

		mdelay(1);

	}



	clear_bit(0, &backtrace_flag);

	smp_mb__after_clear_bit();

}



/*

 * ipi_cpu_backtrace - handle IPI from smp_send_all_cpu_backtrace()

 */

static void ipi_cpu_backtrace(unsigned int cpu, struct pt_regs *regs)

{

	if (cpu_isset(cpu, backtrace_mask)) {

		raw_spin_lock(&backtrace_lock);

		pr_warn("IPI backtrace for cpu %d\n", cpu);

		show_regs(regs);

		raw_spin_unlock(&backtrace_lock);

		cpu_clear(cpu, backtrace_mask);

	}

}



#ifdef CONFIG_SMP

void arch_trigger_all_cpu_backtrace(void)

{

	smp_send_all_cpu_backtrace();

}

#else

void arch_trigger_all_cpu_backtrace(void)

{

	dump_stack();

}

#endif





/*

 * Main handler for inter-processor interrupts

 */
@@ -634,6 +702,9 @@ void handle_IPI(int ipinr, struct pt_regs *regs) 
		irq_exit();

		break;

#endif

	case IPI_CPU_BACKTRACE:

		ipi_cpu_backtrace(cpu, regs);

		break;



	default:

		pr_crit("CPU%u: Unknown IPI message 0x%x\n", cpu, ipinr);

include/linux/nmi.h

+2 −3
Original line number Diff line number Diff line
@@ -48,7 +48,7 @@ static inline bool watchdog_hardlockup_detector_is_enabled(void) 
#ifdef arch_trigger_all_cpu_backtrace

static inline bool trigger_all_cpu_backtrace(void)

{

	#if defined(CONFIG_ARM)

	#if defined(CONFIG_ARM) || defined(CONFIG_ARM64)

	arch_trigger_all_cpu_backtrace();

	#else

	arch_trigger_all_cpu_backtrace(true);
@@ -58,13 +58,12 @@ static inline bool trigger_all_cpu_backtrace(void) 
}

static inline bool trigger_allbutself_cpu_backtrace(void)

{

	#if defined(CONFIG_ARM)

	#if defined(CONFIG_ARM) || defined(CONFIG_ARM64)

	arch_trigger_all_cpu_backtrace();

	#else

	arch_trigger_all_cpu_backtrace(false);

	#endif





	return true;

}

#else