The patch titled
Subject: kill do_each_thread()
has been added to the -mm mm-nonmm-unstable branch. Its filename is
kill-do_each_thread.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/kill-do_each_thread.patch
This patch will later appear in the mm-nonmm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Oleg Nesterov <oleg@xxxxxxxxxx>
Subject: kill do_each_thread()
Date: Thu, 17 Aug 2023 18:37:08 +0200
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@xxxxxxxxxx
Signed-off-by: Oleg Nesterov <oleg@xxxxxxxxxx>
Reviewed-by: Kees Cook <keescook@xxxxxxxxxxxx>
Cc: "Christian Brauner (Microsoft)" <brauner@xxxxxxxxxx>
Cc: Eric W. Biederman <ebiederm@xxxxxxxxxxxx>
Cc: Jiri Slaby <jirislaby@xxxxxxxxxx> # tty/serial
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
arch/ia64/kernel/mca.c | 4 ++--
drivers/tty/tty_io.c | 4 ++--
fs/fs_struct.c | 4 ++--
include/linux/sched/signal.h | 7 -------
4 files changed, 6 insertions(+), 13 deletions(-)
--- a/arch/ia64/kernel/mca.c~kill-do_each_thread
+++ a/arch/ia64/kernel/mca.c
@@ -1630,10 +1630,10 @@ default_monarch_init_process(struct noti
}
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. */
--- a/drivers/tty/tty_io.c~kill-do_each_thread
+++ a/drivers/tty/tty_io.c
@@ -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);
}
--- a/fs/fs_struct.c~kill-do_each_thread
+++ a/fs/fs_struct.c
@@ -62,7 +62,7 @@ void chroot_fs_refs(const struct path *o
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 *o
spin_unlock(&fs->lock);
}
task_unlock(p);
- } while_each_thread(g, p);
+ }
read_unlock(&tasklist_lock);
while (count--)
path_put(old_root);
--- a/include/linux/sched/signal.h~kill-do_each_thread
+++ a/include/linux/sched/signal.h
@@ -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)
_
Patches currently in -mm which might be from oleg@xxxxxxxxxx are
kill-do_each_thread.patch
