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From: ebiederm@xmission.com (Eric W. Biederman)
To: Oleg Nesterov <oleg@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
	LKML <linux-kernel@vger.kernel.org>,
	Linux FS Devel <linux-fsdevel@vger.kernel.org>,
	Alexey Dobriyan <adobriyan@gmail.com>,
	Alexey Gladkov <legion@kernel.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Alexey Gladkov <gladkov.alexey@gmail.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	"Paul E. McKenney" <paulmck@kernel.org>
Subject: Re: [PATCH v4 0/2] proc: Ensure we see the exit of each process tid exactly
Date: Tue, 28 Apr 2020 13:54:43 -0500	[thread overview]
Message-ID: <875zdj8mq4.fsf@x220.int.ebiederm.org> (raw)
In-Reply-To: <20200428180540.GB29960@redhat.com> (Oleg Nesterov's message of "Tue, 28 Apr 2020 20:05:41 +0200")

Oleg Nesterov <oleg@redhat.com> writes:

> On 04/28, Eric W. Biederman wrote:
>>
>> In short I don't think this change will introduce any regressions.
>>
>> Eric W. Biederman (2):
>>       rculist: Add hlists_swap_heads_rcu
>>       proc: Ensure we see the exit of each process tid exactly once
>
> Eric, sorry, I got lost.
>
> Both changes look good to me, feel free to add my ack, but I presume
> this is on top of next_tgid/lookup_task changes ? If yes, why did not
> you remove has_group_leader_pid?

On top of next_tgid.

Upon a close examination there are not any current bugs in
posix-cpu-timers nor is there anything that exchange_tids
will make worse.

I am preparing a follow on patchset to kill has_group_leader_pid.

I am preparing a further follow on patchset to see if I can get that
code to start returning pids, because that is cheaper and clearer.


I pushed those changes a little farther out so I could maintain focus on
what I am accomplishing.

Adding exchange_tids was difficult because I had to audit pretty much
all of the pid use in the kernel to see if the small change in behavior
would make anything worse.   The rest of the changes should be simpler
and more localized so I hope they go faster.

Eric


  reply	other threads:[~2020-04-28 18:58 UTC|newest]

Thread overview: 54+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-04-19 14:10 [PATCH v12 0/7] proc: modernize proc to support multiple private instances Alexey Gladkov
2020-04-19 14:10 ` [PATCH v12 1/7] proc: rename struct proc_fs_info to proc_fs_opts Alexey Gladkov
2020-04-19 14:10 ` [PATCH v12 2/7] proc: allow to mount many instances of proc in one pid namespace Alexey Gladkov
2020-04-23 11:28   ` [PATCH v13 " Alexey Gladkov
2020-04-23 12:16     ` Eric W. Biederman
2020-04-23 20:01       ` Alexey Gladkov
2020-04-19 14:10 ` [PATCH v12 3/7] proc: instantiate only pids that we can ptrace on 'hidepid=4' mount option Alexey Gladkov
2020-04-19 14:10 ` [PATCH v12 4/7] proc: add option to mount only a pids subset Alexey Gladkov
2020-04-19 14:10 ` [PATCH v12 5/7] docs: proc: add documentation for "hidepid=4" and "subset=pid" options and new mount behavior Alexey Gladkov
2020-04-19 14:10 ` [PATCH v12 6/7] proc: use human-readable values for hidepid Alexey Gladkov
2020-04-19 14:10 ` [PATCH v12 7/7] proc: use named enums for better readability Alexey Gladkov
     [not found] ` <87ftcv1nqe.fsf@x220.int.ebiederm.org>
2020-04-23 17:54   ` [PATCH v2 0/2] proc: Calling proc_flush_task exactly once per task Oleg Nesterov
2020-04-23 19:38     ` Eric W. Biederman
2020-04-23 19:39   ` [PATCH v2 1/2] proc: Use PIDTYPE_TGID in next_tgid Eric W. Biederman
2020-04-24 17:29     ` Oleg Nesterov
2020-04-23 19:39   ` [PATCH v2 2/2] proc: Ensure we see the exit of each process tid exactly Eric W. Biederman
2020-04-23 20:28     ` Linus Torvalds
2020-04-24  3:33       ` Eric W. Biederman
2020-04-24 18:02         ` Linus Torvalds
2020-04-24 18:46           ` Linus Torvalds
2020-04-24 19:51           ` Eric W. Biederman
2020-04-24 20:10             ` Linus Torvalds
2020-04-24 17:39     ` Oleg Nesterov
2020-04-24 18:10       ` Eric W. Biederman
2020-04-24 20:50       ` [PATCH] proc: Put thread_pid in release_task not proc_flush_pid Eric W. Biederman
     [not found]       ` <87mu6ymkea.fsf_-_@x220.int.ebiederm.org>
     [not found]         ` <87blnemj5t.fsf_-_@x220.int.ebiederm.org>
2020-04-26 17:22           ` [PATCH v3 2/6] posix-cpu-timers: Use PIDTYPE_TGID to simplify the logic in lookup_task Oleg Nesterov
2020-04-27 11:51             ` Eric W. Biederman
2020-04-28 18:03               ` Oleg Nesterov
2020-04-27 10:32           ` Thomas Gleixner
2020-04-27 19:46             ` Eric W. Biederman
     [not found]         ` <875zdmmj4y.fsf_-_@x220.int.ebiederm.org>
2020-04-26 17:40           ` [PATCH v3 3/6] rculist: Add hlist_swap_before_rcu Linus Torvalds
2020-04-27 14:28             ` Eric W. Biederman
2020-04-27 20:27               ` Linus Torvalds
2020-04-28 12:16                 ` [PATCH v4 0/2] proc: Ensure we see the exit of each process tid exactly Eric W. Biederman
2020-04-28 12:18                   ` [PATCH v4 1/2] rculist: Add hlists_swap_heads_rcu Eric W. Biederman
2020-04-28 12:19                   ` [PATCH v4 2/2] proc: Ensure we see the exit of each process tid exactly once Eric W. Biederman
2020-04-28 16:53                   ` [PATCH v4 0/2] proc: Ensure we see the exit of each process tid exactly Linus Torvalds
2020-04-28 17:55                     ` Eric W. Biederman
2020-04-28 18:55                     ` Eric W. Biederman
2020-04-28 19:36                       ` Linus Torvalds
2020-04-28 18:05                   ` Oleg Nesterov
2020-04-28 18:54                     ` Eric W. Biederman [this message]
2020-04-28 21:39                     ` [PATCH v1 0/4] signal: Removing has_group_leader_pid Eric W. Biederman
2020-04-28 21:45                       ` [PATCH v1 1/4] posix-cpu-timer: Tidy up group_leader logic in lookup_task Eric W. Biederman
2020-04-28 21:48                       ` [PATCH 2/4] posix-cpu-timer: Unify the now redundant code " Eric W. Biederman
2020-04-28 21:53                       ` [PATCH v1 3/4] exec: Remove BUG_ON(has_group_leader_pid) Eric W. Biederman
2020-04-28 21:56                       ` [PATCH v4 4/4] signal: Remove has_group_leader_pid Eric W. Biederman
2020-04-30 11:54                       ` [PATCH v1 0/3] posix-cpu-timers: Use pids not tasks in lookup Eric W. Biederman
2020-04-30 11:55                         ` [PATCH v1 1/3] posix-cpu-timers: Extend rcu_read_lock removing task_struct references Eric W. Biederman
2020-04-30 11:56                         ` [PATCH v1 2/3] posix-cpu-timers: Replace cpu_timer_pid_type with clock_pid_type Eric W. Biederman
2020-04-30 11:56                         ` [PATCH v1 3/3] posix-cpu-timers: Replace __get_task_for_clock with pid_for_clock Eric W. Biederman
     [not found]         ` <87h7x6mj6h.fsf_-_@x220.int.ebiederm.org>
2020-04-27  9:43           ` [PATCH v3 1/6] posix-cpu-timers: Always call __get_task_for_clock holding rcu_read_lock Thomas Gleixner
2020-04-27 11:53             ` Eric W. Biederman
     [not found]         ` <87r1w8ete7.fsf@x220.int.ebiederm.org>
2020-04-27 20:23           ` [PATCH v3] proc: Ensure we see the exit of each process tid exactly Eric W. Biederman

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