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, 28 insertions, 6 deletions

diff --git a/sys/kern/kern_resource.c b/sys/kern/kern_resource.c
index ffcd488..c15c631 100644
--- a/sys/kern/kern_resource.c
+++ b/sys/kern/kern_resource.c
@@ -111,14 +111,25 @@ getpriority(td, uap)
 	case PRIO_PGRP: {
 		register struct pgrp *pg;
 
-		if (uap->who == 0)
+		PGRPSESS_SLOCK();
+		if (uap->who == 0) {
 			pg = curp->p_pgrp;
-		else if ((pg = pgfind(uap->who)) == NULL)
-			break;
+			PGRP_LOCK(pg);
+		} else {
+			pg = pgfind(uap->who);
+			if (pg == NULL) {
+				PGRPSESS_SUNLOCK();
+				break;
+			}
+		}
+		PGRPSESS_SUNLOCK();
 		LIST_FOREACH(p, &pg->pg_members, p_pglist) {
+			PROC_LOCK(p);
 			if (!p_cansee(curp, p) && p->p_ksegrp.kg_nice /* XXXKSE */  < low)
 				low = p->p_ksegrp.kg_nice /* XXXKSE */ ;
+			PROC_UNLOCK(p);
 		}
+		PGRP_UNLOCK(pg);
 		break;
 	}
 
@@ -185,16 +196,27 @@ setpriority(td, uap)
 	case PRIO_PGRP: {
 		register struct pgrp *pg;
 
-		if (uap->who == 0)
+		PGRPSESS_SLOCK();
+		if (uap->who == 0) {
 			pg = curp->p_pgrp;
-		else if ((pg = pgfind(uap->who)) == NULL)
-			break;
+			PGRP_LOCK(pg);
+		} else {
+			pg = pgfind(uap->who);
+			if (pg == NULL) {
+				PGRPSESS_SUNLOCK();
+				break;
+			}
+		}
+		PGRPSESS_SUNLOCK();
 		LIST_FOREACH(p, &pg->pg_members, p_pglist) {
+			PROC_LOCK(p);
 			if (!p_cansee(curp, p)) {
 				error = donice(curp, p, uap->prio);
 				found++;
 			}
+			PROC_UNLOCK(p);
 		}
+		PGRP_UNLOCK(pg);
 		break;
 	}