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From: Konstantin Belousov <kib@FreeBSD.org>
Date: Sat, 23 May 2015 19:09:04 +0000 (UTC)
To: src-committers@freebsd.org, svn-src-all@freebsd.org,
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Subject: svn commit: r283320 - head/sys/kern
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Author: kib
Date: Sat May 23 19:09:04 2015
New Revision: 283320
URL: https://svnweb.freebsd.org/changeset/base/283320

Log:
  If thread requested to not stop on non-boundary, then not only
  stopping signals should obey, but also all forms of single-threading.
  Otherwise, thread might sleep interruptible while owning some
  resources, and single-threading thread could try to access them.
  An example is owning vnode lock while dumping core.
  
  Submitted by:	Conrad Meyer
  Review:	https://reviews.freebsd.org/D2612
  Tested by:	pho
  MFC after:	1 week

Modified:
  head/sys/kern/kern_thread.c

Modified: head/sys/kern/kern_thread.c
==============================================================================
--- head/sys/kern/kern_thread.c	Sat May 23 17:48:09 2015	(r283319)
+++ head/sys/kern/kern_thread.c	Sat May 23 19:09:04 2015	(r283320)
@@ -868,12 +868,9 @@ thread_suspend_check(int return_instead)
 			return (ERESTART);
 
 		/*
-		 * Ignore suspend requests for stop signals if they
-		 * are deferred.
+		 * Ignore suspend requests if they are deferred.
 		 */
-		if ((P_SHOULDSTOP(p) == P_STOPPED_SIG ||
-		    (p->p_flag & P_TOTAL_STOP) != 0) &&
-		    (td->td_flags & TDF_SBDRY) != 0) {
+		if ((td->td_flags & TDF_SBDRY) != 0) {
 			KASSERT(return_instead,
 			    ("TDF_SBDRY set for unsafe thread_suspend_check"));
 			return (0);