Document why calling smp_call_function will deadlock when called with
interrupts disabled.
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
diff --git a/arch/mips/kernel/smp.c b/arch/mips/kernel/smp.c
index af5cd3b..1d3a4b5 100644
--- a/arch/mips/kernel/smp.c
+++ b/arch/mips/kernel/smp.c
@@ -121,7 +121,19 @@
* or are or have executed.
*
* You must not call this function with disabled interrupts or from a
- * hardware interrupt handler or from a bottom half handler.
+ * hardware interrupt handler or from a bottom half handler:
+ *
+ * CPU A CPU B
+ * Disable interrupts
+ * smp_call_function()
+ * Take call_lock
+ * Send IPIs
+ * Wait for all cpus to acknowledge IPI
+ * CPU A has not responded, spin waiting
+ * for cpu A to respond, holding call_lock
+ * smp_call_function()
+ * Spin waiting for call_lock
+ * Deadlock Deadlock
*/
int smp_call_function (void (*func) (void *info), void *info, int retry,
int wait)