Commit 5ffd2c37 authored by Oleg Nesterov's avatar Oleg Nesterov Committed by Andrew Morton
Browse files

kill do_each_thread() 

Eric has pointed out that we still have 3 users of do_each_thread().
Change them to use for_each_process_thread() and kill this helper.

There is a subtle change, after do_each_thread/while_each_thread g == t ==
&init_task, while after for_each_process_thread() they both point to
nowhere, but this doesn't matter.

> Why is for_each_process_thread() better than do_each_thread()?

Say, for_each_process_thread() is rcu safe, do_each_thread() is not.

And certainly

	for_each_process_thread(p, t) {
		do_something(p, t);
	}

looks better than

	do_each_thread(p, t) {
		do_something(p, t);
	} while_each_thread(p, t);

And again, there are only 3 users of this awkward helper left.  It should
have been killed years ago and in fact I thought it had already been
killed.  It uses while_each_thread() which needs some changes.

Link: https://lkml.kernel.org/r/20230817163708.GA8248@redhat.com


Signed-off-by: default avatarOleg Nesterov <oleg@redhat.com>
Reviewed-by: default avatarKees Cook <keescook@chromium.org>
Cc: "Christian Brauner (Microsoft)" <brauner@kernel.org>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Jiri Slaby <jirislaby@kernel.org> # tty/serial
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent cdaac8e7

arch/ia64/kernel/mca.c

+2 −2
Original line number Diff line number Diff line
@@ -1630,10 +1630,10 @@ default_monarch_init_process(struct notifier_block *self, unsigned long val, voi 
	}

	printk("\n\n");

	if (read_trylock(&tasklist_lock)) {

		do_each_thread (g, t) {

		for_each_process_thread(g, t) {

			printk("\nBacktrace of pid %d (%s)\n", t->pid, t->comm);

			show_stack(t, NULL, KERN_DEFAULT);

		} while_each_thread (g, t);

		}

		read_unlock(&tasklist_lock);

	}

	/* FIXME: This will not restore zapped printk locks. */

drivers/tty/tty_io.c

+2 −2
Original line number Diff line number Diff line
@@ -3031,7 +3031,7 @@ void __do_SAK(struct tty_struct *tty) 
	} while_each_pid_task(session, PIDTYPE_SID, p);



	/* Now kill any processes that happen to have the tty open */

	do_each_thread(g, p) {

	for_each_process_thread(g, p) {

		if (p->signal->tty == tty) {

			tty_notice(tty, "SAK: killed process %d (%s): by controlling tty\n",

				   task_pid_nr(p), p->comm);
@@ -3048,7 +3048,7 @@ void __do_SAK(struct tty_struct *tty) 
					PIDTYPE_SID);

		}

		task_unlock(p);

	} while_each_thread(g, p);

	}

	read_unlock(&tasklist_lock);

	put_pid(session);

}

fs/fs_struct.c

+2 −2
Original line number Diff line number Diff line
@@ -62,7 +62,7 @@ void chroot_fs_refs(const struct path *old_root, const struct path *new_root) 
	int count = 0;



	read_lock(&tasklist_lock);

	do_each_thread(g, p) {

	for_each_process_thread(g, p) {

		task_lock(p);

		fs = p->fs;

		if (fs) {
@@ -79,7 +79,7 @@ void chroot_fs_refs(const struct path *old_root, const struct path *new_root) 
			spin_unlock(&fs->lock);

		}

		task_unlock(p);

	} while_each_thread(g, p);

	}

	read_unlock(&tasklist_lock);

	while (count--)

		path_put(old_root);

include/linux/sched/signal.h

+0 −7
Original line number Diff line number Diff line
@@ -648,13 +648,6 @@ extern void flush_itimer_signals(void); 


extern bool current_is_single_threaded(void);



/*

 * Careful: do_each_thread/while_each_thread is a double loop so

 *          'break' will not work as expected - use goto instead.

 */

#define do_each_thread(g, t) \

	for (g = t = &init_task ; (g = t = next_task(g)) != &init_task ; ) do



#define while_each_thread(g, t) \

	while ((t = next_thread(t)) != g)