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From: Oleg Nesterov <oleg@redhat.com>
To: Andrii Nakryiko <andrii.nakryiko@gmail.com>
Cc: Masami Hiramatsu <mhiramat@kernel.org>,
	Andrii Nakryiko <andrii@kernel.org>,
	linux-trace-kernel@vger.kernel.org, rostedt@goodmis.org,
	peterz@infradead.org, mingo@redhat.com, bpf@vger.kernel.org,
	jolsa@kernel.org, paulmck@kernel.org, clm@meta.com
Subject: Re: [PATCH 02/12] uprobes: grab write mmap lock in unapply_uprobe()
Date: Tue, 25 Jun 2024 21:07:49 +0200	[thread overview]
Message-ID: <20240625190748.GC14254@redhat.com> (raw)
In-Reply-To: <CAEf4BzZqGNVqAmk_wrGP+MmxQidEr4=FdYiYpodpRd1TAib81A@mail.gmail.com>

On 06/25, Andrii Nakryiko wrote:
>
> On Tue, Jun 25, 2024 at 7:51 AM Oleg Nesterov <oleg@redhat.com> wrote:
> >
> > Why?
> >
> > So far I don't understand this change. Quite possibly I missed something,
> > but in this case the changelog should explain the problem more clearly.
> >
>
> I just went off of "Called with mm->mmap_lock held for write." comment
> in uprobe_write_opcode(), tbh.

Ah, indeed... and git blame makes me sad ;)

I _think_ that 29dedee0e693a updated this comment without any thinking,
but today I can't recall. In any case, today this nothing to do with
mem_cgroup_charge(). Not sure __replace_page() is correct (in this respect)
when it returns -EAGAIN but this is another story.

> If we don't actually need writer
> mmap_lock, we should probably update at least that comment.

Agreed.

> There is a
> lot going on in uprobe_write_opcode(), and I don't understand all the
> requirements there.

Heh. Neither me today ;)

Oleg.


  reply	other threads:[~2024-06-25 19:09 UTC|newest]

Thread overview: 42+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2024-06-25  0:21 [PATCH 00/12] uprobes: add batched register/unregister APIs and per-CPU RW semaphore Andrii Nakryiko
2024-06-25  0:21 ` [PATCH 01/12] uprobes: update outdated comment Andrii Nakryiko
2024-06-25  0:21 ` [PATCH 02/12] uprobes: grab write mmap lock in unapply_uprobe() Andrii Nakryiko
2024-06-25  1:29   ` Masami Hiramatsu
2024-06-25 14:49     ` Oleg Nesterov
2024-06-25 17:37       ` Andrii Nakryiko
2024-06-25 19:07         ` Oleg Nesterov [this message]
2024-06-26 16:38           ` Andrii Nakryiko
2024-06-25 10:50   ` Oleg Nesterov
2024-06-25  0:21 ` [PATCH 03/12] uprobes: simplify error handling for alloc_uprobe() Andrii Nakryiko
2024-06-25  0:21 ` [PATCH 04/12] uprobes: revamp uprobe refcounting and lifetime management Andrii Nakryiko
2024-06-25 14:44   ` Oleg Nesterov
2024-06-25 17:30     ` Andrii Nakryiko
2024-06-26  6:02   ` kernel test robot
2024-06-26 16:39     ` Andrii Nakryiko
2024-06-27  2:29   ` Masami Hiramatsu
2024-06-27 16:43     ` Andrii Nakryiko
2024-07-01 21:59       ` Andrii Nakryiko
2024-06-25  0:21 ` [PATCH 05/12] uprobes: move offset and ref_ctr_offset into uprobe_consumer Andrii Nakryiko
2024-06-27  3:06   ` Masami Hiramatsu
2024-06-25  0:21 ` [PATCH 06/12] uprobes: add batch uprobe register/unregister APIs Andrii Nakryiko
2024-06-26 11:27   ` Jiri Olsa
2024-06-26 16:44     ` Andrii Nakryiko
2024-06-27 13:04   ` Masami Hiramatsu
2024-06-27 16:47     ` Andrii Nakryiko
2024-06-28  6:28       ` Masami Hiramatsu
2024-06-28 16:34         ` Andrii Nakryiko
2024-06-29 23:30           ` Masami Hiramatsu
2024-07-01 17:55             ` Andrii Nakryiko
2024-07-01 22:15               ` Andrii Nakryiko
2024-07-02  1:01                 ` Masami Hiramatsu
2024-07-02  1:34                   ` Andrii Nakryiko
2024-07-02 15:19                     ` Masami Hiramatsu
2024-07-02 16:53                       ` Steven Rostedt
2024-07-02 21:23                         ` Andrii Nakryiko
2024-07-02 23:16                         ` Masami Hiramatsu
2024-06-25  0:21 ` [PATCH 07/12] uprobes: inline alloc_uprobe() logic into __uprobe_register() Andrii Nakryiko
2024-06-25  0:21 ` [PATCH 08/12] uprobes: split uprobe allocation and uprobes_tree insertion steps Andrii Nakryiko
2024-06-25  0:21 ` [PATCH 09/12] uprobes: batch uprobes_treelock during registration Andrii Nakryiko
2024-06-25  0:21 ` [PATCH 10/12] uprobes: improve lock batching for uprobe_unregister_batch Andrii Nakryiko
2024-06-25  0:21 ` [PATCH 11/12] uprobes,bpf: switch to batch uprobe APIs for BPF multi-uprobes Andrii Nakryiko
2024-06-25  0:21 ` [PATCH 12/12] uprobes: switch uprobes_treelock to per-CPU RW semaphore Andrii Nakryiko

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