linux-kernel - Re: [PATCHv4 02/14] uprobe: Add support for session consumer

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Message-ID: <20240923100552.GA20793@redhat.com>
Date: Mon, 23 Sep 2024 12:05:53 +0200
From: Oleg Nesterov <oleg@...hat.com>
To: Jiri Olsa <olsajiri@...il.com>
Cc: Peter Zijlstra <peterz@...radead.org>,
	Alexei Starovoitov <ast@...nel.org>,
	Daniel Borkmann <daniel@...earbox.net>,
	Andrii Nakryiko <andrii@...nel.org>, bpf@...r.kernel.org,
	Martin KaFai Lau <kafai@...com>, Song Liu <songliubraving@...com>,
	Yonghong Song <yhs@...com>,
	John Fastabend <john.fastabend@...il.com>,
	KP Singh <kpsingh@...omium.org>,
	Stanislav Fomichev <sdf@...ichev.me>, Hao Luo <haoluo@...gle.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Masami Hiramatsu <mhiramat@...nel.org>,
	linux-kernel@...r.kernel.org, linux-trace-kernel@...r.kernel.org
Subject: Re: [PATCHv4 02/14] uprobe: Add support for session consumer

On 09/23, Jiri Olsa wrote:
>
> change below should do what you proposed originally

LGTM, just one nit below.

But I guess you need to do this on top of bpf/bpf.git, Andrii has already
applied your series.

And to remind, 02/14 must be fixed in any case unless I am totally confused,
handler_chain() can leak return_instance.

> also on top of that.. I discussed with Andrii the possibility of dropping
> the UPROBE_HANDLER_IWANTMYCOOKIE completely and setup cookie for any consumer
> that has both 'handler' and 'ret_handler' defined, wdyt?

Up to you. As I said from the very beginning I won't insist on _IWANTMYCOOKIE.

>  	list_for_each_entry_srcu(uc, &uprobe->consumers, cons_node,
>  				 srcu_read_lock_held(&uprobes_srcu)) {
> +		ric = return_consumer_find(ri, &ric_idx, uc->id);
>  		if (uc->ret_handler)
> -			uc->ret_handler(uc, ri->func, regs);
> +			uc->ret_handler(uc, ri->func, regs, ric ? &ric->cookie : NULL);
>  	}
>  	srcu_read_unlock(&uprobes_srcu, srcu_idx);

return_consumer_find() makes no sense if !uc->ret_handler, can you move

		ric = return_consumer_find(ri, &ric_idx, uc->id);

into the "if (uc->ret_handler)" block?

Oleg.