linux-kernel - Re: [RFC 2/1] kill task_ucounts()->rcu_read_lock(), add __task

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Message-ID: <2258932.1761576956@warthog.procyon.org.uk>
Date: Mon, 27 Oct 2025 14:55:56 +0000
From: David Howells <dhowells@...hat.com>
To: Oleg Nesterov <oleg@...hat.com>
Cc: dhowells@...hat.com, Alexey Gladkov <legion@...nel.org>,
    Andrew Morton <akpm@...ux-foundation.org>,
    Mateusz Guzik <mjguzik@...il.com>,
    "Paul E. McKenney" <paulmck@...nel.org>,
    linux-kernel@...r.kernel.org
Subject: Re: [RFC 2/1] kill task_ucounts()->rcu_read_lock(), add __task_ucounts()

Oleg Nesterov <oleg@...hat.com> wrote:

> So I think task_ucounts() can just do
> 
> 	/* The caller must ensure that ->real_cred is stable or take rcu_read_lock() */
> 	#define task_ucounts(task)	\
> 		rcu_dereference_check((task)->real_cred, 1)->ucounts

Can you use rcu_access_pointer() within exit.c?  E.g.:

	struct cred *pcreds = rcu_access_pointer(task->real_cred);
	dec_rlimit_ucounts(pcreds->ucounts, UCOUNT_RLIMIT_NPROC, 1);

David