Lock struct pgrp, session and sigio.

New locks are:

- pgrpsess_lock which locks the whole pgrps and sessions,
- pg_mtx which protects the pgrp members, and
- s_mtx which protects the session members.

Please refer to sys/proc.h for the coverage of these locks.

Changes on the pgrp/session interface:

- pgfind() needs the pgrpsess_lock held.

- The caller of enterpgrp() is responsible to allocate a new pgrp and
  session.

- Call enterthispgrp() in order to enter an existing pgrp.

- pgsignal() requires a pgrp lock held.

Reviewed by:	jhb, alfred
Tested on:	cvsup.jp.FreeBSD.org
		(which is a quad-CPU machine running -current)

1 files changed, 8 insertions, 2 deletions

diff --git a/sys/i386/isa/pcvt/pcvt_out.c b/sys/i386/isa/pcvt/pcvt_out.c
index e891b4c..8c77933 100644
--- a/sys/i386/isa/pcvt/pcvt_out.c
+++ b/sys/i386/isa/pcvt/pcvt_out.c
@@ -1582,8 +1582,11 @@ set_emulation_mode(struct video_state *svsp, int mode)
 		svsp->scrr_end = svsp->scrr_len - 1;
 	}
 
-	if (svsp->vs_tty && svsp->vs_tty->t_pgrp)
+	if (svsp->vs_tty && svsp->vs_tty->t_pgrp) {
+		PGRP_LOCK(svsp->vs_tty->t_pgrp);
 		pgsignal(svsp->vs_tty->t_pgrp, SIGWINCH, 1);
+		PGRP_UNLOCK(svsp->vs_tty->t_pgrp);
+	}
 }
 
 /*---------------------------------------------------------------------------*
@@ -1867,8 +1870,11 @@ vt_col(struct video_state *svsp, int cols)
 			(cols == SCR_COL80)? 720: 1056;
 		svsp->vs_tty->t_winsize.ws_ypixel = 400;
 
-		if(svsp->vs_tty->t_pgrp)
+		if(svsp->vs_tty->t_pgrp) {
+			PGRP_LOCK(svsp->vs_tty->t_pgrp);
 			pgsignal(svsp->vs_tty->t_pgrp, SIGWINCH, 1);
+			PGRP_UNLOCK(svsp->vs_tty->t_pgrp);
+		}
 	}
 
 	reallocate_scrollbuffer(svsp, svsp->scrollback_pages);