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Tue, 08 Sep 2026 10:22:47 -0700 (PDT) Date: Tue, 8 Sep 2026 20:26:54 +0300 From: Alexey Dobriyan To: "Lorenzo Stoakes (ARM)" Cc: Ye Liu , Tony Luck , Reinette Chatre , x86@kernel.org, Christian Brauner , Andrew Morton , Jann Horn , "David Hildenbrand (arm)" , "Mike Rapoport (Microsoft)" , Oleg Nesterov , Ye Liu , Dave Martin , James Morse , Babu Moger , linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org Subject: Re: [PATCH 6/8] fs: convert process/thread iterators to for_each_*_rcu Message-ID: <16df546d-46b5-42c1-a8ca-24cde0051a97@p183> References: <20260904083001.553587-1-ye.liu@linux.dev> <20260904083001.553587-7-ye.liu@linux.dev> <662ade9d-d662-4f6f-869f-08c41da53170@p183> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: On Tue, Sep 08, 2026 at 06:10:17PM +0100, Lorenzo Stoakes (ARM) wrote: > On Tue, Sep 08, 2026 at 07:45:15PM +0300, Alexey Dobriyan wrote: > > On Fri, Sep 04, 2026 at 04:29:58PM +0800, Ye Liu wrote: > > > --- a/fs/proc/base.c > > > +++ b/fs/proc/base.c > > > @@ -1160,8 +1160,7 @@ static int __set_oom_adj(struct file *file, int oom_adj, bool legacy) > > > if (mm) { > > > struct task_struct *p; > > > > > > - rcu_read_lock(); > > > - for_each_process(p) { > > > + for_each_process_rcu(p) { > > > if (same_thread_group(task, p)) > > > continue; > > > > > > @@ -1177,7 +1176,6 @@ static int __set_oom_adj(struct file *file, int oom_adj, bool legacy) > > > } > > > task_unlock(p); > > > } > > > - rcu_read_unlock(); > > > mmdrop(mm); > > > } > > > err_unlock: > > > > What's going on here? > > Now it's RCU unlock after mmdrop(). > > No it's not, scoped_guard() is scoped to the for_each_process_rcu() block which > ends before mmdrop(), i.e. the exact same scope as before. > > That closing '}' is attached to the if (mm). OK. I think naming (and macro) are misguided: * _rcu means "use under RCU section opened elsewhere", this one is "I open and close RCU section myself". * not every 2 lines should be combined into new interface.