linux-kernel - Re: [PATCH v4 4/8] uprobes: travers uprobe's consumer list locklessly under SRCU protection

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Message-ID: <20240830143151.GC20163@redhat.com>
Date: Fri, 30 Aug 2024 16:31:51 +0200
From: Oleg Nesterov <oleg@...hat.com>
To: Jiri Olsa <olsajiri@...il.com>
Cc: Andrii Nakryiko <andrii.nakryiko@...il.com>,
	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, paulmck@...nel.org,
	willy@...radead.org, surenb@...gle.com, akpm@...ux-foundation.org,
	linux-mm@...ck.org
Subject: Re: [PATCH v4 4/8] uprobes: travers uprobe's consumer list
 locklessly under SRCU protection

On 08/30, Jiri Olsa wrote:
>
> with this change the probe will not get removed in the attached test,
> it'll get 2 hits, without this change just 1 hit

I don't understand the code in tools/...bpf../ at all, can't comment,

> but I'm not sure it's a big problem, because seems like that's not the
> intended way the removal should be used anyway, as explained by Oleg [1]

It seems that I confused you again ;)

No, I think you found a problem. UPROBE_HANDLER_REMOVE can be lost if
uc->filter == NULL of if it returns true. See another reply I sent a
minute ago.

I think the fix is simple, plus we need to cleanup this logic anyway,
I'll try to send some code on Monday.

Oleg.