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)

4 files changed, 21 insertions, 8 deletions

diff --git a/sys/fs/coda/coda_venus.c b/sys/fs/coda/coda_venus.c
index 022009e..e223617 100644
--- a/sys/fs/coda/coda_venus.c
+++ b/sys/fs/coda/coda_venus.c
@@ -94,13 +94,11 @@
 
 #define INIT_IN(in, op, ident, p) \
 	  (in)->opcode = (op); \
-	  if (p) \
-	      PROC_LOCK(p); \
+	  PGRPSESS_SLOCK(); \
 	  (in)->pid = p ? p->p_pid : -1; \
           (in)->pgid = p ? p->p_pgid : -1; \
           (in)->sid = (p && p->p_session && p->p_session->s_leader) ? (p->p_session->s_leader->p_pid) : -1; \
-	  if (p) \
-	      PROC_UNLOCK(p); \
+	  PGRPSESS_SUNLOCK(); \
           if (ident != NOCRED) {                              \
 	      (in)->cred.cr_uid = ident->cr_uid;              \
 	      (in)->cred.cr_groupid = ident->cr_gid;          \
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");
 	}
diff --git a/sys/fs/specfs/spec_vnops.c b/sys/fs/specfs/spec_vnops.c
index 9de659c..7887ddb 100644
--- a/sys/fs/specfs/spec_vnops.c
+++ b/sys/fs/specfs/spec_vnops.c
@@ -35,6 +35,8 @@
  */
 
 #include <sys/param.h>
+#include <sys/lock.h>
+#include <sys/sx.h>
 #include <sys/proc.h>
 #include <sys/systm.h>
 #include <sys/kernel.h>
@@ -568,7 +570,7 @@ spec_close(ap)
 		struct thread *a_td;
 	} */ *ap;
 {
-	struct vnode *vp = ap->a_vp;
+	struct vnode *vp = ap->a_vp, *oldvp;
 	struct thread *td = ap->a_td;
 	dev_t dev = vp->v_rdev;
 
@@ -581,11 +583,18 @@ spec_close(ap)
 	 * if the reference count is 2 (this last descriptor
 	 * plus the session), release the reference from the session.
 	 */
+	oldvp = NULL;
+	PGRPSESS_XLOCK();
 	if (vcount(vp) == 2 && td && (vp->v_flag & VXLOCK) == 0 &&
 	    vp == td->td_proc->p_session->s_ttyvp) {
-		vrele(vp);
+		SESS_LOCK(td->td_proc->p_session);
 		td->td_proc->p_session->s_ttyvp = NULL;
+		SESS_UNLOCK(td->td_proc->p_session);
+		oldvp = vp;
 	}
+	PGRPSESS_XUNLOCK();
+	if (oldvp != NULL)
+		vrele(oldvp);
 	/*
 	 * We do not want to really close the device if it
 	 * is still in use unless we are trying to close it