Do not send signals to init directly from shutdown_nice(9), do it from

the task context.

shutdown_nice() is used from the fast interrupt handlers, mostly for
console drivers, where we cannot lock blockable locks.  Schedule the
task in the fast queue to send the signal from the proper context.

Reviewed by:	imp
Discussed with:	bde
Sponsored by:	The FreeBSD Foundation
MFC after:	1 week

1 files changed, 30 insertions, 13 deletions

diff --git a/sys/kern/kern_shutdown.c b/sys/kern/kern_shutdown.c
index e64e1dd39b62..ea16f1fa99d3 100644
--- a/sys/kern/kern_shutdown.c
+++ b/sys/kern/kern_shutdown.c
@@ -72,6 +72,7 @@ __FBSDID("$FreeBSD$");
 #include <sys/smp.h>
 #include <sys/sysctl.h>
 #include <sys/sysproto.h>
+#include <sys/taskqueue.h>
 #include <sys/vnode.h>
 #include <sys/watchdog.h>
 
@@ -276,6 +277,28 @@ sys_reboot(struct thread *td, struct reboot_args *uap)
 	return (error);
 }
 
+static void
+shutdown_nice_task_fn(void *arg, int pending __unused)
+{
+	int howto;
+
+	howto = (uintptr_t)arg;
+	/* Send a signal to init(8) and have it shutdown the world. */
+	PROC_LOCK(initproc);
+	if (howto & RB_POWEROFF)
+		kern_psignal(initproc, SIGUSR2);
+	else if (howto & RB_POWERCYCLE)
+		kern_psignal(initproc, SIGWINCH);
+	else if (howto & RB_HALT)
+		kern_psignal(initproc, SIGUSR1);
+	else
+		kern_psignal(initproc, SIGINT);
+	PROC_UNLOCK(initproc);
+}
+
+static struct task shutdown_nice_task = TASK_INITIALIZER(0,
+    &shutdown_nice_task_fn, NULL);
+
 /*
  * Called by events that want to shut down.. e.g  <CTL><ALT><DEL> on a PC
  */
@@ -283,20 +306,14 @@ void
 shutdown_nice(int howto)
 {
 
-	if (initproc != NULL) {
-		/* Send a signal to init(8) and have it shutdown the world. */
-		PROC_LOCK(initproc);
-		if (howto & RB_POWEROFF)
-			kern_psignal(initproc, SIGUSR2);
-		else if (howto & RB_POWERCYCLE)
-			kern_psignal(initproc, SIGWINCH);
-		else if (howto & RB_HALT)
-			kern_psignal(initproc, SIGUSR1);
-		else
-			kern_psignal(initproc, SIGINT);
-		PROC_UNLOCK(initproc);
+	if (initproc != NULL && !SCHEDULER_STOPPED()) {
+		shutdown_nice_task.ta_context = (void *)(uintptr_t)howto;
+		taskqueue_enqueue(taskqueue_fast, &shutdown_nice_task);
 	} else {
-		/* No init(8) running, so simply reboot. */
+		/*
+		 * No init(8) running, or scheduler would not allow it
+		 * to run, so simply reboot.
+		 */
 		kern_reboot(howto | RB_NOSYNC);
 	}
 }