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Message-ID: <c6c86d68-dcae-2397-a3f3-aca7bff93d6c@kernel.org>
Date:   Fri, 18 Aug 2023 10:25:26 +0200
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Subject: Re: [PATCH] kill do_each_thread()
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To:     Oleg Nesterov <oleg@redhat.com>
Cc:     Andrew Morton <akpm@linux-foundation.org>,
        "Eric W. Biederman" <ebiederm@xmission.com>,
        Christian Brauner <brauner@kernel.org>,
        Kees Cook <keescook@chromium.org>, linux-ia64@vger.kernel.org,
        linux-kernel@vger.kernel.org
References: <20230817163708.GA8248@redhat.com>
 <d92e7938-49e0-3b4c-89ab-77dcd15b8676@kernel.org>
 <20230818081617.GA5339@redhat.com>
From:   Jiri Slaby <jirislaby@kernel.org>
In-Reply-To: <20230818081617.GA5339@redhat.com>
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On 18. 08. 23, 10:16, Oleg Nesterov wrote:
> On 08/18, Jiri Slaby wrote:
>>
>> On 17. 08. 23, 18:37, Oleg Nesterov wrote:
>>> Eric has pointed out that we still have 3 users of do_each_thread().
>>> Change them to use for_each_process_thread() and kill this helper.
>>
>> Is there any change in behavior?
> 
> No.
> 
> Well, there is a subtle change, after do_each_thread/while_each_thread
> g == t == &init_task, while after for_each_process_thread() they both
> point to nowhere, but this doesn't matter.
> 
>> Why is for_each_process_thread() better than do_each_thread()?
> 
> Say, for_each_process_thread() is rcu safe, do_each_thread() is not.
> 
> And certainly
> 
> 	for_each_process_thread(p, t) {
> 		do_something(p, t);
> 	}
> 
> looks better than
> 
> 	do_each_thread(p, t) {
> 		do_something(p, t);
> 	} while_each_thread(p, t);
> 
> And again, there are only 3 users of this awkward helper left.
> It should have been killed years ago and in fact I thought it
> had already been killed. It uses while_each_thread() which needs
> some changes.

Sounds like a perfect commit log now... Unless squashed to the patch, it 
will be Linked at least. Thanks for explanation.

-- 
js
suse labs