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)

2 files changed, 8 insertions, 2 deletions

diff --git a/sys/fs/procfs/procfs_ctl.c b/sys/fs/procfs/procfs_ctl.c
index 154eaa6..3a73980 100644
--- a/sys/fs/procfs/procfs_ctl.c
+++ b/sys/fs/procfs/procfs_ctl.c
@@ -230,8 +230,10 @@ out:
 
 			pp = pfind(p->p_oppid);
 			PROC_LOCK(p);
-			if (pp)
+			if (pp) {
+				PROC_UNLOCK(pp);
 				proc_reparent(p, pp);
+			}
 		} else
 			PROC_LOCK(p);
 		p->p_oppid = 0;
diff --git a/sys/fs/procfs/procfs_status.c b/sys/fs/procfs/procfs_status.c
index 0f8e343..9238dfe 100644
--- a/sys/fs/procfs/procfs_status.c
+++ b/sys/fs/procfs/procfs_status.c
@@ -48,6 +48,8 @@
 #include <sys/mutex.h>
 #include <sys/jail.h>
 #include <sys/malloc.h>
+#include <sys/mutex.h>
+#include <sys/sx.h>
 #include <sys/proc.h>
 #include <sys/resourcevar.h>
 #include <sys/sbuf.h>
@@ -75,9 +77,9 @@ procfs_doprocstatus(PFS_FILL_ARGS)
 	pid = p->p_pid;
 	PROC_LOCK(p);
 	ppid = p->p_pptr ? p->p_pptr->p_pid : 0;
-	PROC_UNLOCK(p);
 	pgid = p->p_pgrp->pg_id;
 	sess = p->p_pgrp->pg_session;
+	SESS_LOCK(sess);
 	sid = sess->s_leader ? sess->s_leader->p_pid : 0;
 
 /* comm pid ppid pgid sid maj,min ctty,sldr start ut st wmsg 
@@ -106,6 +108,8 @@ procfs_doprocstatus(PFS_FILL_ARGS)
 		sbuf_printf(sb, "%ssldr", sep);
 		sep = ",";
 	}
+	SESS_UNLOCK(sess);
+	PROC_UNLOCK(p);
 	if (*sep != ',') {
 		sbuf_printf(sb, "noflags");
 	}