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From: Konstantin Belousov <kib@FreeBSD.org>
Date: Sun, 27 Oct 2013 16:20:52 +0000 (UTC)
To: src-committers@freebsd.org, svn-src-all@freebsd.org,
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Subject: svn commit: r257214 - head/sys/kern
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Author: kib
Date: Sun Oct 27 16:20:52 2013
New Revision: 257214
URL: http://svnweb.freebsd.org/changeset/base/257214

Log:
  When reentering kdb, typically due to a bug causing trap or assert in
  the code executed in the context of debugger, do not be ashamed to
  inform loudly about the re-entry.  Also, print the backtrace before
  obliterating current stack with longjmp, allowing the operator to see
  a place which caused the bug.
  
  The change should make it less mysterious debugging the ddb itself.
  
  Sponsored by:	The FreeBSD Foundation
  MFC after:	1 week

Modified:
  head/sys/kern/subr_kdb.c

Modified: head/sys/kern/subr_kdb.c
==============================================================================
--- head/sys/kern/subr_kdb.c	Sun Oct 27 16:18:48 2013	(r257213)
+++ head/sys/kern/subr_kdb.c	Sun Oct 27 16:20:52 2013	(r257214)
@@ -503,6 +503,8 @@ kdb_reenter(void)
 	if (!kdb_active || kdb_jmpbufp == NULL)
 		return;
 
+	printf("KDB: reentering\n");
+	kdb_backtrace();
 	longjmp(kdb_jmpbufp, 1);
 	/* NOTREACHED */
 }