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, 3 insertions, 3 deletions

diff --git a/sys/kern/sys_process.c b/sys/kern/sys_process.c
index 018734e..e15f191 100644
--- a/sys/kern/sys_process.c
+++ b/sys/kern/sys_process.c
@@ -515,10 +515,10 @@ ptrace(struct thread *td, struct ptrace_args *uap)
 				struct proc *pp;
 
 				pp = pfind(p->p_oppid);
-				if (pp != NULL)
-					PROC_UNLOCK(pp);
-				else
+				if (pp == NULL)
 					pp = initproc;
+				else
+					PROC_UNLOCK(pp);
 				PROC_LOCK(p);
 				proc_reparent(p, pp);
 			} else