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/kernel/smp.c b/arch/arm/kernel/smp.c
index e7f92a4..b50b8dd 100644
--- a/arch/arm/kernel/smp.c
+++ b/arch/arm/kernel/smp.c
@@ -53,6 +53,7 @@
IPI_CALL_FUNC,
IPI_CALL_FUNC_SINGLE,
IPI_CPU_STOP,
+ IPI_CPU_BACKTRACE,
};
int __cpuinit __cpu_up(unsigned int cpu)
@@ -405,6 +406,7 @@
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 @@
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 @@
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);