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)

3 files changed, 12 insertions, 3 deletions

diff --git a/sys/compat/linprocfs/linprocfs.c b/sys/compat/linprocfs/linprocfs.c
index 06f0f38..ae21891 100644
--- a/sys/compat/linprocfs/linprocfs.c
+++ b/sys/compat/linprocfs/linprocfs.c
@@ -494,9 +494,9 @@ linprocfs_doprocstat(PFS_FILL_ARGS)
 	PS_ADD("statr",		"%c",	'0'); /* XXX */
 	PROC_LOCK(p);
 	PS_ADD("ppid",		"%d",	p->p_pptr ? p->p_pptr->p_pid : 0);
-	PROC_UNLOCK(p);
 	PS_ADD("pgrp",		"%d",	p->p_pgid);
 	PS_ADD("session",	"%d",	p->p_session->s_sid);
+	PROC_UNLOCK(p);
 	PS_ADD("tty",		"%d",	0); /* XXX */
 	PS_ADD("tpgid",		"%d",	0); /* XXX */
 	PS_ADD("flags",		"%u",	0); /* XXX */
diff --git a/sys/compat/linux/linux_file.c b/sys/compat/linux/linux_file.c
index 1dfa4a1..dd4f219 100644
--- a/sys/compat/linux/linux_file.c
+++ b/sys/compat/linux/linux_file.c
@@ -144,12 +144,13 @@ linux_open(struct thread *td, struct linux_open_args *args)
 			fo_ioctl(fp, TIOCSCTTY, (caddr_t) 0, td);
 	    fdrop(fp, td);
 	}
-    } else
+    } else {
 	PROC_UNLOCK(p);
 #ifdef DEBUG
 	if (ldebug(open))
 		printf(LMSG("open returns error %d"), error);
 #endif
+    }
     return error;
 }
 
diff --git a/sys/compat/svr4/svr4_misc.c b/sys/compat/svr4/svr4_misc.c
index 4771d90..9dcfa7f 100644
--- a/sys/compat/svr4/svr4_misc.c
+++ b/sys/compat/svr4/svr4_misc.c
@@ -1017,7 +1017,9 @@ svr4_sys_pgrpsys(td, uap)
 		/*FALLTHROUGH*/
 
 	case 0:			/* getpgrp() */
+		PROC_LOCK(p);
 		*retval = p->p_pgrp->pg_id;
+		PROC_UNLOCK(p);
 		return 0;
 
 	case 2:			/* getsid(pid) */
@@ -1222,7 +1224,9 @@ svr4_sys_waitsys(td, uap)
 		break;
 
 	case SVR4_P_PGID:
+		PROC_LOCK(td->td_proc);
 		SCARG(uap, id) = -td->td_proc->p_pgid;
+		PROC_UNLOCK(td->td_proc);
 		break;
 
 	case SVR4_P_ALL:
@@ -1283,8 +1287,12 @@ loop:
 				if (q->p_oppid != q->p_pptr->p_pid) {
 					PROC_UNLOCK(q);
 					t = pfind(q->p_oppid);
+					if (t == NULL) {
+						t = initproc;
+						PROC_LOCK(initproc);
+					}
 					PROC_LOCK(q);
-					proc_reparent(q, t ? t : initproc);
+					proc_reparent(q, t);
  					q->p_oppid = 0;
 					q->p_flag &= ~(P_TRACED | P_WAITED);
 					PROC_UNLOCK(q);