Disable suspend when we're shutting down. This solves the "tell FreeBSD

to shut down; close laptop lid" scenario which otherwise tended to end
with a laptop overheating or the battery dying.

The implementation uses a new sysctl, kern.suspend_blocked; init(8) sets
this while rc.suspend runs, and the ACPI sleep code ignores requests while
the sysctl is set.

Discussed on:	freebsd-acpi (35 emails)
MFC after:	1 week

1 files changed, 14 insertions, 0 deletions

diff --git a/sbin/init/init.c b/sbin/init/init.c
index 5ab3527..edc38e6 100644
--- a/sbin/init/init.c
+++ b/sbin/init/init.c
@@ -1487,6 +1487,15 @@ static state_func_t
 death(void)
 {
 	session_t *sp;
+	int block, blocked;
+	size_t len;
+
+	/* Temporarily block suspend. */
+	len = sizeof(blocked);
+	block = 1;
+	if (sysctlbyname("kern.suspend_blocked", &blocked, &len,
+	    &block, sizeof(block)) == -1)
+		blocked = 0;
 
 	/*
 	 * Also revoke the TTY here.  Because runshutdown() may reopen
@@ -1503,6 +1512,11 @@ death(void)
 	/* Try to run the rc.shutdown script within a period of time */
 	runshutdown();
 
+	/* Unblock suspend if we blocked it. */
+	if (!blocked)
+		sysctlbyname("kern.suspend_blocked", NULL, NULL,
+		    &blocked, sizeof(blocked));
+
 	return (state_func_t) death_single;
 }