If a cpu is spinning in the kernel but still responding to interrupts,
pressing sysrq-y will show you where it's spinning.
Signed-off-by: Avi Kivity <[email protected]>
diff --git a/drivers/char/sysrq.c b/drivers/char/sysrq.c
index 39cc318..1dda709 100644
--- a/drivers/char/sysrq.c
+++ b/drivers/char/sysrq.c
@@ -45,6 +45,8 @@ int __read_mostly __sysrq_enabled = 1;
static int __read_mostly sysrq_always_enabled;
+static spinlock_t show_stack_lock = SPIN_LOCK_UNLOCKED;
+
int sysrq_on(void)
{
return __sysrq_enabled || sysrq_always_enabled;
@@ -309,6 +311,26 @@ static struct sysrq_key_op sysrq_unrt_op = {
.enable_mask = SYSRQ_ENABLE_RTNICE,
};
+static void show_cpu_stack(void *garbage)
+{
+ spin_lock(&show_stack_lock);
+ printk("CPU%d stacktrace:\n", raw_smp_processor_id());
+ dump_stack();
+ sysrq_handle_showregs(0, NULL);
+ spin_unlock(&show_stack_lock);
+}
+
+static void sysrq_show_stacks(int key, struct tty_struct *tty)
+{
+ on_each_cpu(show_cpu_stack, NULL, 0, 1);
+}
+
+static struct sysrq_key_op sysrq_show_stacks_op = {
+ .handler = sysrq_show_stacks,
+ .help_msg = "stacktraces-on-all-cpus(Y)",
+ .action_msg = "Stack traces on all cpus",
+};
+
/* Key Operations table and lock */
static DEFINE_SPINLOCK(sysrq_key_table_lock);
@@ -356,7 +378,7 @@ static struct sysrq_key_op *sysrq_key_table[36] = {
&sysrq_showstate_blocked_op, /* w */
/* x: May be registered on ppc/powerpc for xmon */
NULL, /* x */
- NULL, /* y */
+ &sysrq_show_stacks_op, /* y */
NULL /* z */
};
-
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