Re: [PATCH][RESEND 3] disassociate_ctty SMP fix

[Rik van Riel]

On Tue, 4 Feb 2003, Rik van Riel wrote:

> the following patch, against today's BK tree, fixes a small
> SMP race in disassociate_ctty.  This function gets called
> from do_exit, without the BKL held.

Here's a better one, this one does the same fix not only
in disassociate_ctty() but also in do_tty_hangup()

If we're lucky it might fix:
http://bugme.osdl.org/show_bug.cgi?id=54

Please apply. Thank you,

Rik

===== drivers/char/tty_io.c 1.55 vs edited =====
--- 1.55/drivers/char/tty_io.c	Tue Jan 14 23:37:20 2003
+++ edited/drivers/char/tty_io.c	Tue Feb  4 23:02:52 2003
@@ -425,19 +425,21 @@
  */
 void do_tty_hangup(void *data)
 {
-	struct tty_struct *tty = (struct tty_struct *) data;
+	struct tty_struct *tty;
 	struct file * cons_filp = NULL;
 	struct task_struct *p;
 	struct list_head *l;
 	struct pid *pid;
 	int    closecount = 0, n;

-	if (!tty)
-		return;
-
 	/* inuse_filps is protected by the single kernel lock */
 	lock_kernel();
-
+	tty = (struct tty_struct *) data;
+	if (!tty) {
+		unlock_kernel();
+		return;
+	}
+
 	check_tty_count(tty, "do_tty_hangup");
 	file_list_lock();
 	for (l = tty->tty_files.next; l != &tty->tty_files; l = l->next) {
@@ -571,7 +573,7 @@
  */
 void disassociate_ctty(int on_exit)
 {
-	struct tty_struct *tty = current->tty;
+	struct tty_struct *tty;
 	struct task_struct *p;
 	struct list_head *l;
 	struct pid *pid;
@@ -579,6 +581,7 @@

 	lock_kernel();

+	tty = current->tty;
 	if (tty) {
 		tty_pgrp = tty->pgrp;
 		if (on_exit && tty->driver.type != TTY_DRIVER_TYPE_PTY)