diff options
| author | Oleg Nesterov <oleg@redhat.com> | 2026-10-11 16:16:51 +0200 |
|---|---|---|
| committer | Christian Brauner <brauner@kernel.org> | 2026-10-12 10:39:51 +0200 |
| commit | 41e24dc80739b07d592566ceeaf0bb5e3620cc5c (patch) | |
| tree | be3d15625e0a7c9d05b8db0a5be43360b558ea0e /include/linux | |
| parent | ed14a591175bb5f56c2936b082cffb9e4b935e6d (diff) | |
| download | linux-41e24dc80739b07d592566ceeaf0bb5e3620cc5c.tar.gz linux-41e24dc80739b07d592566ceeaf0bb5e3620cc5c.zip | |
pid: document that do_each_pid_task() needs tasklist_lock
do_each_pid_task() looks "obviously rcu-safe". This confuses people
and we already have 2 buggy users: send_sigio() and send_sigurg().
The reasons why it is not are not obvious at all, add the comment.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Link: https://patch.msgid.link/asuaU8H_5MbO3-cW@redhat.com
Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
Diffstat (limited to 'include/linux')
| -rw-r--r-- | include/linux/pid.h | 9 |
1 files changed, 9 insertions, 0 deletions
diff --git a/include/linux/pid.h b/include/linux/pid.h index ddaef0bbc8ba..f5476d7140a3 100644 --- a/include/linux/pid.h +++ b/include/linux/pid.h @@ -187,6 +187,15 @@ static inline pid_t pid_nr(struct pid *pid) pid_t pid_nr_ns(struct pid *pid, struct pid_namespace *ns); pid_t pid_vnr(struct pid *pid); +/* + * Needs tasklist_lock if type > PIDTYPE_TGID. A lockless reader can: + * + * - race with a change_pid() that moves the task to another hlist, + * and continue to scan the wrong list. + * + * - race with a copy_process() that adds a new task to the start of hlist, + * and miss the new child. + */ #define do_each_pid_task(pid, type, task) \ do { \ if ((pid) != NULL) \ |