linux-kernel - Re: [PATCH net-next 1/2] connector/cn_proc: Handle threads for proc connector

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Message-ID: <6D9B4443-4293-4EC8-A64A-1CDDB2CE4E4E@oracle.com>
Date: Fri, 20 Sep 2024 19:39:02 +0000
From: Anjali Kulkarni <anjali.k.kulkarni@...cle.com>
To: Oleg Nesterov <oleg@...hat.com>
CC: "davem@...emloft.net" <davem@...emloft.net>,
        Liam Howlett
	<liam.howlett@...cle.com>,
        "edumazet@...gle.com" <edumazet@...gle.com>,
        "kuba@...nel.org" <kuba@...nel.org>,
        "pabeni@...hat.com" <pabeni@...hat.com>,
        "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
        "axboe@...nel.dk"
	<axboe@...nel.dk>,
        "brauner@...nel.org" <brauner@...nel.org>,
        "mhocko@...e.com" <mhocko@...e.com>,
        "alexjlzheng@...cent.com"
	<alexjlzheng@...cent.com>,
        "willy@...radead.org" <willy@...radead.org>,
        Michael Christie <michael.christie@...cle.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "shuah@...nel.org"
	<shuah@...nel.org>,
        "linux-kselftest@...r.kernel.org"
	<linux-kselftest@...r.kernel.org>,
        Pei Li <peili.io@...cle.com>,
        "Eric W.
 Biederman" <ebiederm@...ssion.com>
Subject: Re: [PATCH net-next 1/2] connector/cn_proc: Handle threads for proc
 connector



> On Sep 20, 2024, at 11:44 AM, Oleg Nesterov <oleg@...hat.com> wrote:
> 
> On 09/20, Anjali Kulkarni wrote:
>> 
>>> On Sep 20, 2024, at 4:00 AM, Oleg Nesterov <oleg@...hat.com> wrote:
>>> 
>>> I don't think you can use task_struct->exit_code. If this task is ptraced,
>>> it can be changed/cleared in, say, ptrace_stop() after PROC_CN_MCAST_NOTIFY.
>>> 
>> 
>> Thank you, that’s a good point! However, the use case of ptrace, which I assume
>> is for mostly debug and tracing, is exclusive of the use case I am using it for
> 
> Well. I don't understand your use-case. Or any other use-case for drivers/connector/
> that I know nothing about. But this is irrelevant.
> 
> The new PROC_CN_MCAST_NOTIFY functionality you propose should work regardless of

Yes, agreed.

> whether this task is ptraced or not. But it doesn't because the usage of ->exit_code
> in your patch conflicts with the current usage of this field.
> 
Ok, I see that ptrace_stop() seems to be using it in much the same way I want to use it - as a temporary place to store some values. Since in do_exit(), exit_code is overwritten, I didn’t think anyone was using it.
Could I add a new field in the task_struct to store my value? (I don’t think there is any other unused/field I can use temporarily)

Anjali

> So, NACK, sorry.
> 
> Oleg.
>