From 5ffd2c37cb7a53d52099e5ed1fd7ccbc9e358791 Mon Sep 17 00:00:00 2001 From: Oleg Nesterov Date: Thu, 17 Aug 2023 18:37:08 +0200 Subject: [PATCH] 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: Oleg Nesterov Reviewed-by: Kees Cook Cc: "Christian Brauner (Microsoft)" Cc: Eric W. Biederman Cc: Jiri Slaby # tty/serial Signed-off-by: Andrew Morton --- 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(-) diff --git a/arch/ia64/kernel/mca.c b/arch/ia64/kernel/mca.c index 92ede80d17fe..2671688d349a 100644 --- a/arch/ia64/kernel/mca.c +++ b/arch/ia64/kernel/mca.c @@ -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. */ diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c index 63db04b9113a..27d8e3a1aace 100644 --- a/drivers/tty/tty_io.c +++ b/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); } diff --git a/fs/fs_struct.c b/fs/fs_struct.c index 04b3f5b9c629..64c2d0814ed6 100644 --- a/fs/fs_struct.c +++ b/fs/fs_struct.c @@ -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); diff --git a/include/linux/sched/signal.h b/include/linux/sched/signal.h index 669e8cff40c7..0deebe2ab07d 100644 --- a/include/linux/sched/signal.h +++ b/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)