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Commit d4dcc857 authored by Dima Zavin's avatar Dima Zavin Committed by Ruchi Kandoi
Browse files

ARM: smp: implement arch_trigger_all_cpus_backtrace using IPI 



Based on a rough patch by frank.rowand@am.sony.com

Since ARM doesn't have an NMI (fiq's are not always available),
send an IPI to all other CPUs (current cpu prints the stack directly)
to capture a backtrace.

Change-Id: I8b163c8cec05d521b433ae133795865e8a33d4e2
Signed-off-by: default avatarDima Zavin <dima@android.com>
parent 7e0e7017

arch/arm/include/asm/hardirq.h

+1 −1
Original line number Diff line number Diff line
@@ -5,7 +5,7 @@ 
#include <linux/threads.h>

#include <asm/irq.h>



#define NR_IPI	8

#define NR_IPI	9



typedef struct {

	unsigned int __softirq_pending;

arch/arm/include/asm/irq.h

+3 −0
Original line number Diff line number Diff line
@@ -35,6 +35,9 @@ extern void (*handle_arch_irq)(struct pt_regs *); 
extern void set_handle_irq(void (*handle_irq)(struct pt_regs *));

#endif



void arch_trigger_all_cpu_backtrace(void);

#define arch_trigger_all_cpu_backtrace arch_trigger_all_cpu_backtrace



#endif



#endif

arch/arm/include/asm/smp.h

+2 −0
Original line number Diff line number Diff line
@@ -81,6 +81,8 @@ extern void arch_send_wakeup_ipi_mask(const struct cpumask *mask); 


extern int register_ipi_completion(struct completion *completion, int cpu);



extern void smp_send_all_cpu_backtrace(void);



struct smp_operations {

#ifdef CONFIG_SMP

	/*

arch/arm/kernel/process.c

+12 −0
Original line number Diff line number Diff line
@@ -59,6 +59,18 @@ static const char *isa_modes[] __maybe_unused = { 
  "ARM" , "Thumb" , "Jazelle", "ThumbEE"

};



#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



extern void call_with_stack(void (*fn)(void *), void *arg, void *sp);

typedef void (*phys_reset_t)(unsigned long);

arch/arm/kernel/smp.c

+58 −0
Original line number Diff line number Diff line
@@ -72,6 +72,7 @@ enum ipi_msg_type { 
	IPI_CPU_STOP,

	IPI_IRQ_WORK,

	IPI_COMPLETION,

	IPI_CPU_BACKTRACE,

};



static DECLARE_COMPLETION(cpu_running);
@@ -447,6 +448,7 @@ static const char *ipi_types[NR_IPI] __tracepoint_string = { 
	S(IPI_CPU_STOP, "CPU stop interrupts"),

	S(IPI_IRQ_WORK, "IRQ work interrupts"),

	S(IPI_COMPLETION, "completion interrupts"),

	S(IPI_CPU_BACKTRACE, "CPU backtrace"),

};



static void smp_cross_call(const struct cpumask *target, unsigned int ipinr)
@@ -548,6 +550,58 @@ static void ipi_complete(unsigned int cpu) 
	complete(per_cpu(cpu_completion, cpu));

}



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;



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");

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

		show_regs(regs);

		raw_spin_unlock(&backtrace_lock);

		cpu_clear(cpu, backtrace_mask);

	}

}



/*

 * Main handler for inter-processor interrupts

 */
@@ -614,6 +668,10 @@ void handle_IPI(int ipinr, struct pt_regs *regs) 
		irq_exit();

		break;



	case IPI_CPU_BACKTRACE:

		ipi_cpu_backtrace(cpu, regs);

		break;



	default:

		printk(KERN_CRIT "CPU%u: Unknown IPI message 0x%x\n",

		       cpu, ipinr);