Author: imp
Date: Thu Mar 22 15:34:37 2018
New Revision: 331362
URL: https://svnweb.freebsd.org/changeset/base/331362
Log:
Drop any recursed taking of Giant once and for all at the top of
kern_reboot(). The shutdown path is now safe to run without Giant.
Discussed with: kib@
Sponsored by: Netflix
Modified:
head/sys/kern/kern_shutdown.c
Modified: head/sys/kern/kern_shutdown.c
==============================================================================
--- head/sys/kern/kern_shutdown.c Thu Mar 22 15:32:57 2018
(r331361)
+++ head/sys/kern/kern_shutdown.c Thu Mar 22 15:34:37 2018
(r331362)
@@ -366,6 +366,17 @@ kern_reboot(int howto)
{
static int once = 0;
+ /*
+ * Normal paths here don't hold Giant, but we can wind up here
+ * unexpectedly with it held. Drop it now so we don't have to
+ * drop and pick it up elsewhere. The paths it is locking will
+ * never be returned to, and it is preferable to preclude
+ * deadlock than to lock against code that won't ever
+ * continue.
+ */
+ while (mtx_owned(&Giant))
+ mtx_unlock(&Giant);
+
#if defined(SMP)
/*
* Bind us to the first CPU so that all shutdown code runs there. Some
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