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authorOleg Nesterov <oleg@redhat.com>2023-08-23 20:08:06 +0300
committerAndrew Morton <akpm@linux-foundation.org>2023-08-25 02:25:15 +0300
commitdce8f8ed1de1d9d6d27c5ccd202ce4ec163b100c (patch)
tree93e6156402383138221d53cb0937d28cefa97cf0 /fs/proc
parented1af26cd24811c3ddb5e7a276e3c6362c989bba (diff)
downloadlinux-dce8f8ed1de1d9d6d27c5ccd202ce4ec163b100c.tar.xz
document while_each_thread(), change first_tid() to use for_each_thread()
Add the comment to explain that while_each_thread(g,t) is not rcu-safe unless g is stable (e.g. current). Even if g is a group leader and thus can't exit before t, t or another sub-thread can exec and remove g from the thread_group list. The only lockless user of while_each_thread() is first_tid() and it is fine in that it can't loop forever, yet for_each_thread() looks better and I am going to change while_each_thread/next_thread. Link: https://lkml.kernel.org/r/20230823170806.GA11724@redhat.com Signed-off-by: Oleg Nesterov <oleg@redhat.com> Cc: Eric W. Biederman <ebiederm@xmission.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Diffstat (limited to 'fs/proc')
-rw-r--r--fs/proc/base.c5
1 files changed, 2 insertions, 3 deletions
diff --git a/fs/proc/base.c b/fs/proc/base.c
index 05452c3b9872..483a3edebdd1 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -3813,11 +3813,10 @@ static struct task_struct *first_tid(struct pid *pid, int tid, loff_t f_pos,
/* If we haven't found our starting place yet start
* with the leader and walk nr threads forward.
*/
- pos = task = task->group_leader;
- do {
+ for_each_thread(task, pos) {
if (!nr--)
goto found;
- } while_each_thread(task, pos);
+ };
fail:
pos = NULL;
goto out;