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, 4 insertions, 0 deletions

diff --git a/sys/kern/kern_acct.c b/sys/kern/kern_acct.c
index cd191d5..e859057 100644
--- a/sys/kern/kern_acct.c
+++ b/sys/kern/kern_acct.c
@@ -233,10 +233,14 @@ acct_process(td)
 	acct.ac_gid = p->p_ucred->cr_rgid;
 
 	/* (7) The terminal from which the process was started */
+	PROC_LOCK(p);
+	SESS_LOCK(p->p_session);
 	if ((p->p_flag & P_CONTROLT) && p->p_pgrp->pg_session->s_ttyp)
 		acct.ac_tty = dev2udev(p->p_pgrp->pg_session->s_ttyp->t_dev);
 	else
 		acct.ac_tty = NOUDEV;
+	SESS_UNLOCK(p->p_session);
+	PROC_UNLOCK(p);
 
 	/* (8) The boolean flags that tell how the process terminated, etc. */
 	acct.ac_flag = p->p_acflag;