linux-kernel.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
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 0/6] bpf: task_group_seq_get_next: use __next_thread()
Date: Fri, 25 Aug 2023 18:18:42 +0200	[thread overview]
Message-ID: <20230825161842.GA16750@redhat.com> (raw)

Compile tested, 1-5 need the review from bpf maintainers, quite possibly
I did some silly mistakes. I tried to cleanup this code because I could
not look at it, but it has other problems and imo should be rewritten.

6/6 obviously depends on

	[PATCH 1/2] introduce __next_thread(), fix next_tid() vs exec() race
	https://lore.kernel.org/all/20230824143142.GA31222@redhat.com/

which was not merged yet.

To simplify the review, this is the code after 6/6:

	static struct task_struct *task_group_seq_get_next(struct bpf_iter_seq_task_common *common,
							   u32 *tid,
							   bool skip_if_dup_files)
	{
		struct task_struct *task;
		struct pid *pid;
		u32 next_tid;

		if (!*tid) {
			/* The first time, the iterator calls this function. */
			pid = find_pid_ns(common->pid, common->ns);
			task = get_pid_task(pid, PIDTYPE_TGID);
			if (!task)
				return NULL;

			*tid = common->pid;
			common->pid_visiting = common->pid;

			return task;
		}

		/* If the control returns to user space and comes back to the
		 * kernel again, *tid and common->pid_visiting should be the
		 * same for task_seq_start() to pick up the correct task.
		 */
		if (*tid == common->pid_visiting) {
			pid = find_pid_ns(common->pid_visiting, common->ns);
			task = get_pid_task(pid, PIDTYPE_PID);

			return task;
		}

		task = find_task_by_pid_ns(common->pid_visiting, common->ns);
		if (!task)
			return NULL;

	retry:
		task = __next_thread(task);
		if (!task)
			return NULL;

		next_tid = __task_pid_nr_ns(task, PIDTYPE_PID, common->ns);
		if (!next_tid)
			goto retry;

		if (skip_if_dup_files && task->files == task->group_leader->files)
			goto retry;

		*tid = common->pid_visiting = next_tid;
		get_task_struct(task);
		return task;
	}

Oleg.


             reply	other threads:[~2023-08-25 16:21 UTC|newest]

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-08-25 16:18 Oleg Nesterov [this message]
2023-08-25 16:19 ` [PATCH 1/6] bpf: task_group_seq_get_next: cleanup the usage of next_thread() Oleg Nesterov
2023-08-25 22:45   ` 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

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20230825161842.GA16750@redhat.com \
    --to=oleg@redhat.com \
    --cc=akpm@linux-foundation.org \
    --cc=andrii@kernel.org \
    --cc=bpf@vger.kernel.org \
    --cc=daniel@iogearbox.net \
    --cc=ebiederm@xmission.com \
    --cc=kuifeng@fb.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=martin.lau@kernel.org \
    --cc=torvalds@linux-foundation.org \
    --cc=yhs@fb.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).