linux-kernel - Re: [PATCH 2/8] uprobes: revamp uprobe refcounting and lifetime management

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Message-ID: <20240802085040.GA12343@redhat.com>
Date: Fri, 2 Aug 2024 10:50:41 +0200
From: Oleg Nesterov <oleg@...hat.com>
To: Andrii Nakryiko <andrii.nakryiko@...il.com>
Cc: Andrii Nakryiko <andrii@...nel.org>, linux-trace-kernel@...r.kernel.org,
	peterz@...radead.org, rostedt@...dmis.org, mhiramat@...nel.org,
	bpf@...r.kernel.org, linux-kernel@...r.kernel.org, jolsa@...nel.org,
	paulmck@...nel.org
Subject: Re: [PATCH 2/8] uprobes: revamp uprobe refcounting and lifetime
 management

On 08/01, Andrii Nakryiko wrote:
>
> > +               /* TODO : cant unregister? schedule a worker thread */
> > +               WARN(err, "leaking uprobe due to failed unregistration");

> Ok, so now that I added this very loud warning if
> register_for_each_vma(uprobe, NULL) returns error, it turns out it's
> not that unusual for this unregistration to fail.

...

> So, is there something smarter we can do in this case besides leaking
> an uprobe (and note, my changes don't change this behavior)?

Something like schedule_work() which retries register_for_each_vma()...

> I can of course just drop the WARN given it's sort of expected now,

Or least replace it with pr_warn() or uprobe_warn(), WARN() certainly
makes no sense imo...

> I don't
> think that should block optimization work, but just something to keep
> in mind and maybe fix as a follow up.

Agreed, lets do this separately.

Oleg.