From: Oleg Nesterov <oleg@redhat.com>
To: Andrew Morton <akpm@linux-foundation.org>, Yonghong Song <yhs@fb.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Kui-Feng Lee <kuifeng@fb.com>,
Andrii Nakryiko <andrii@kernel.org>,
Martin KaFai Lau <martin.lau@kernel.org>,
bpf@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: [PATCH 1/6] bpf: task_group_seq_get_next: cleanup the usage of next_thread()
Date: Fri, 25 Aug 2023 18:19:39 +0200 [thread overview]
Message-ID: <20230825161939.GA16859@redhat.com> (raw)
In-Reply-To: <20230825161842.GA16750@redhat.com>
1. find_pid_ns() + get_pid_task() under rcu_read_lock() guarantees that we
can safely iterate the task->thread_group list. Even if this task exits
right after get_pid_task() (or goto retry) and pid_alive() returns 0.
Kill the unnecessary pid_alive() check.
2. next_thread() simply can't return NULL, kill the bogus "if (!next_task)"
check.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
---
kernel/bpf/task_iter.c | 7 -------
1 file changed, 7 deletions(-)
diff --git a/kernel/bpf/task_iter.c b/kernel/bpf/task_iter.c
index c4ab9d6cdbe9..4d1125108014 100644
--- a/kernel/bpf/task_iter.c
+++ b/kernel/bpf/task_iter.c
@@ -75,15 +75,8 @@ static struct task_struct *task_group_seq_get_next(struct bpf_iter_seq_task_comm
return NULL;
retry:
- if (!pid_alive(task)) {
- put_task_struct(task);
- return NULL;
- }
-
next_task = next_thread(task);
put_task_struct(task);
- if (!next_task)
- return NULL;
saved_tid = *tid;
*tid = __task_pid_nr_ns(next_task, PIDTYPE_PID, common->ns);
--
2.25.1.362.g51ebf55
next prev parent reply other threads:[~2023-08-25 16:22 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-08-25 16:18 [PATCH 0/6] bpf: task_group_seq_get_next: use __next_thread() Oleg Nesterov
2023-08-25 16:19 ` Oleg Nesterov [this message]
2023-08-25 22:45 ` [PATCH 1/6] bpf: task_group_seq_get_next: cleanup the usage of next_thread() Yonghong Song
2023-08-25 16:19 ` [PATCH 2/6] bpf: task_group_seq_get_next: cleanup the usage of get/put_task_struct Oleg Nesterov
2023-08-25 16:19 ` [PATCH 3/6] bpf: task_group_seq_get_next: fix the skip_if_dup_files check Oleg Nesterov
2023-08-25 17:04 ` Oleg Nesterov
2023-08-25 22:52 ` Yonghong Song
2023-08-27 20:19 ` Oleg Nesterov
2023-08-28 1:18 ` Yonghong Song
2023-08-28 10:54 ` Oleg Nesterov
2023-08-29 0:30 ` Yonghong Song
2023-08-30 23:54 ` Oleg Nesterov
2023-08-31 11:29 ` Yonghong Song
2023-08-31 12:06 ` Oleg Nesterov
2023-08-25 22:49 ` Yonghong Song
2023-08-25 16:19 ` [PATCH 4/6] bpf: task_group_seq_get_next: kill next_task Oleg Nesterov
2023-08-25 22:55 ` Yonghong Song
2023-08-25 16:19 ` [PATCH 5/6] bpf: task_group_seq_get_next: simplify the "next tid" logic Oleg Nesterov
2023-08-25 22:57 ` Yonghong Song
2023-08-25 16:19 ` [PATCH 6/6] bpf: task_group_seq_get_next: use __next_thread() rather than next_thread() Oleg Nesterov
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