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kill do_each_thread()

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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: Oleg Nesterov <oleg@redhat.com>
Reviewed-by: Kees 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: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Oleg Nesterov 2023-08-17 18:37:08 +02:00 committed by Andrew Morton
parent cdaac8e7e5
commit 5ffd2c37cb
4 changed files with 6 additions and 13 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
arch/ia64/kernel/mca.c
View File

@ -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. */

4
drivers/tty/tty_io.c
View File

@ -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);
}

4
fs/fs_struct.c
View File

@ -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);

7
include/linux/sched/signal.h
View File

@ -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)