svn commit: r291022 - head/sys/x86/x86

[Roger Pau Monné]

Author: royger
Date: Wed Nov 18 18:09:49 2015
New Revision: 291022
URL: https://svnweb.freebsd.org/changeset/base/291022

Log:
  x86/intr: allow mutex recursion in intr_remove_handler
  
  This is needed so interrupt handlers can be removed while the PIC is
  resuming, it was previously not possible due to intr_resume holding the
  intr_table_lock and intr_remove_handler recursing on it.
  
  Sponsored by:		Citrix Systems R&D
  Reviewed by:		kib (previous version)
  MFC after:		2 weeks
  Differential Revision:	https://reviews.freebsd.org/D4114

Modified:
  head/sys/x86/x86/intr_machdep.c

Modified: head/sys/x86/x86/intr_machdep.c
==============================================================================
--- head/sys/x86/x86/intr_machdep.c	Wed Nov 18 17:52:38 2015	(r291021)
+++ head/sys/x86/x86/intr_machdep.c	Wed Nov 18 18:09:49 2015	(r291022)
@@ -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);
 }