svn commit: r291644 - stable/10/sys/x86/x86

[Roger Pau Monné]

Author: royger
Date: Wed Dec  2 10:23:54 2015
New Revision: 291644
URL: https://svnweb.freebsd.org/changeset/base/291644

Log:
  MFC r291022:
  
  x86/intr: allow mutex recursion in intr_remove_handler
  
  Sponsored by:		Citrix Systems R&D

Modified:
  stable/10/sys/x86/x86/intr_machdep.c
Directory Properties:
  stable/10/   (props changed)

Modified: stable/10/sys/x86/x86/intr_machdep.c
==============================================================================
--- stable/10/sys/x86/x86/intr_machdep.c	Wed Dec  2 08:17:31 2015	(r291643)
+++ stable/10/sys/x86/x86/intr_machdep.c	Wed Dec  2 10:23:54 2015	(r291644)
@@ -197,19 +197,28 @@ int
 intr_remove_handler(void *cookie)
 {
 	struct intsrc *isrc;
-	int error;
+	int error, mtx_owned;
 
 	isrc = intr_handler_source(cookie);
 	error = intr_event_remove_handler(cookie);
 	if (error == 0) {
-		mtx_lock(&intr_table_lock);
+		/*
+		 * Recursion is needed here so PICs can remove interrupts
+		 * while resuming. It was previously not possible due to
+		 * intr_resume holding the intr_table_lock and
+		 * intr_remove_handler recursing on it.
+		 */
+		mtx_owned = mtx_owned(&intr_table_lock);
+		if (mtx_owned == 0)
+			mtx_lock(&intr_table_lock);
 		isrc->is_handlers--;
 		if (isrc->is_handlers == 0) {
 			isrc->is_pic->pic_disable_source(isrc, PIC_NO_EOI);
 			isrc->is_pic->pic_disable_intr(isrc);
 		}
 		intrcnt_updatename(isrc);
-		mtx_unlock(&intr_table_lock);
+		if (mtx_owned == 0)
+			mtx_unlock(&intr_table_lock);
 	}
 	return (error);
 }