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: Dima Zavin <dima@android.com>

diff --git a/arch/arm/include/asm/hardirq.h b/arch/arm/include/asm/hardirq.h
index 89ad180..2635c8b 100644 (file)
--- a/arch/arm/include/asm/hardirq.h
+++ b/arch/arm/include/asm/hardirq.h
@@ -5,7 +5,7 @@
 #include <linux/threads.h>
 #include <asm/irq.h>
 
-#define NR_IPI 5
+#define NR_IPI 6
 
 typedef struct {
        unsigned int __softirq_pending;

diff --git a/arch/arm/include/asm/irq.h b/arch/arm/include/asm/irq.h
index 2721a58..28810c6 100644 (file)
--- a/arch/arm/include/asm/irq.h
+++ b/arch/arm/include/asm/irq.h
@@ -25,6 +25,9 @@ extern void migrate_irqs(void);
 extern void asm_do_IRQ(unsigned int, struct pt_regs *);
 void init_IRQ(void);
 
+void arch_trigger_all_cpu_backtrace(void);
+#define arch_trigger_all_cpu_backtrace arch_trigger_all_cpu_backtrace
+
 #endif
 
 #endif

diff --git a/arch/arm/include/asm/smp.h b/arch/arm/include/asm/smp.h
index e42d96a..74f288f 100644 (file)
--- a/arch/arm/include/asm/smp.h
+++ b/arch/arm/include/asm/smp.h
@@ -93,4 +93,6 @@ extern void arch_send_call_function_ipi_mask(const struct cpumask *mask);
  */
 extern void show_local_irqs(struct seq_file *, int);
 
+extern void smp_send_all_cpu_backtrace(void);
+
 #endif /* ifndef __ASM_ARM_SMP_H */

diff --git a/arch/arm/kernel/process.c b/arch/arm/kernel/process.c
index 34fca2e..6810cc1 100644 (file)
--- a/arch/arm/kernel/process.c
+++ b/arch/arm/kernel/process.c
@@ -62,6 +62,18 @@ static volatile int hlt_counter;
 
 #include <mach/system.h>
 
+#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
+
 void disable_hlt(void)
 {
        hlt_counter++;

diff --git a/arch/arm/kernel/smp.c b/arch/arm/kernel/smp.c
index e7f92a4..b50b8dd 100644 (file)
--- a/arch/arm/kernel/smp.c
+++ b/arch/arm/kernel/smp.c
@@ -53,6 +53,7 @@ enum ipi_msg_type {
        IPI_CALL_FUNC,
        IPI_CALL_FUNC_SINGLE,
        IPI_CPU_STOP,
+       IPI_CPU_BACKTRACE,
 };
 
 int __cpuinit __cpu_up(unsigned int cpu)
@@ -405,6 +406,7 @@ static const char *ipi_types[NR_IPI] = {
        S(IPI_CALL_FUNC, "Function call interrupts"),
        S(IPI_CALL_FUNC_SINGLE, "Single function call interrupts"),
        S(IPI_CPU_STOP, "CPU stop interrupts"),
+       S(IPI_CPU_BACKTRACE, "CPU backtrace"),
 };
 
 void show_ipi_list(struct seq_file *p, int prec)
@@ -555,6 +557,58 @@ static void ipi_cpu_stop(unsigned int cpu)
                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;
+
+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
  */
@@ -587,6 +641,10 @@ asmlinkage void __exception_irq_entry do_IPI(int ipinr, struct pt_regs *regs)
                ipi_cpu_stop(cpu);
                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);