svn commit: r314116 - head/sys/kern

[Jonathan T. Looney]

Author: jtl
Date: Thu Feb 23 01:18:47 2017
New Revision: 314116
URL: https://svnweb.freebsd.org/changeset/base/314116

Log:
  Fix a panic during boot caused by inadequate locking of some vt(4) driver
  data structures.
  
  vt_change_font() calls vtbuf_grow() to change some vt driver data
  structures. It uses TF_MUTE to prevent the console from trying to use those
  data structures while it changes them.
  
  During the early stage of the boot process, the vt driver's tc_done routine
  uses those data structures; however, it is currently called outside the
  TF_MUTE check.
  
  Move the tc_done routine inside the locked TF_MUTE check.
  
  PR:		217282
  Reviewed by:	ed, ray
  Sponsored by:	Netflix
  Differential Revision:	https://reviews.freebsd.org/D9709

Modified:
  head/sys/kern/subr_terminal.c

Modified: head/sys/kern/subr_terminal.c
==============================================================================
--- head/sys/kern/subr_terminal.c	Thu Feb 23 00:02:49 2017	(r314115)
+++ head/sys/kern/subr_terminal.c	Thu Feb 23 01:18:47 2017	(r314116)
@@ -375,7 +375,10 @@ termtty_outwakeup(struct tty *tp)
 		TERMINAL_UNLOCK_TTY(tm);
 	}
 
-	tm->tm_class->tc_done(tm);
+	TERMINAL_LOCK_TTY(tm);
+	if (!(tm->tm_flags & TF_MUTE))
+		tm->tm_class->tc_done(tm);
+	TERMINAL_UNLOCK_TTY(tm);
 	if (flags & TF_BELL)
 		tm->tm_class->tc_bell(tm);
 }
@@ -545,10 +548,9 @@ termcn_cnputc(struct consdev *cp, int c)
 		teken_set_curattr(&tm->tm_emulator, &kernel_message);
 		teken_input(&tm->tm_emulator, &cv, 1);
 		teken_set_curattr(&tm->tm_emulator, &backup);
+		tm->tm_class->tc_done(tm);
 	}
 	TERMINAL_UNLOCK_CONS(tm);
-
-	tm->tm_class->tc_done(tm);
 }
 
 /*