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b=CDdbDc9xHCMS30v5MjFDnxUKCRYcq4sLDVR7heIyRnV3dVUWiz3jSR21p2tC8tLY0 a5ppuV7Oq3pqn1sm26nImkiVnwzWnY4nIQpm5AtJmpDSLfdRBixMkHYcZYNNP+KKIb V+8S6YT+pI9Ac75JoyFDjT5kVsmPyq3bHmp0UAu48vzyqptOu/DDxVdfhBdKPZMXxt LiYaNk1vnoX3Zi8LMh3SGY/hQ7VNY8eF5BGTFWspXDc9TtjKf6v0/YhUdmqpfrdnNY bLDNFrftjN8cE6OpOzzSLk//d9oDXTHlaIIWcd08zyic+FHuWNK9TPoDFmcRsKANU2 WIu8oYXSV7NUA== Date: Mon, 7 Sep 2026 09:30:44 +0100 From: "Lorenzo Stoakes (ARM)" To: Ye Liu Cc: Oleg Nesterov , "Peter Zijlstra (Intel)" , Marco Elver , Ye Liu , Tejun Heo , Christian Brauner , Bart Van Assche , Yi Tao , Michal Hocko , paulmck@kernel.org, mingo@redhat.com, rostedt@goodmis.org, jpoimboe@kernel.org, mic@digikod.net, tglx@kernel.org, akpm@linux-foundation.org, david@kernel.org, linmiaohe@huawei.com, nao.horiguchi@gmail.com, rafael@kernel.org, gnoack3000@gmail.com, sj@kernel.org, rientjes@google.com, shakeel.butt@linux.dev, xu.xin16@zte.com.cn, chengming.zhou@linux.dev, will@kernel.org, boqun@kernel.org, frederic@kernel.org, neeraj.upadhyay@kernel.org, joelagnelf@nvidia.com, josh@joshtriplett.org, urezki@gmail.com, juri.lelli@redhat.com, vincent.guittot@linaro.org, tony.luck@intel.com, reinette.chatre@intel.com, x86@kernel.org, paul@paul-moore.com, jmorris@namei.org, serge@hallyn.com, pavel@kernel.org, lance.yang@linux.dev, mhiramat@kernel.org, pmladek@suse.com, longman@redhat.com, mathieu.desnoyers@efficios.com, jiangshanlai@gmail.com, qiang.zhang@linux.dev, dietmar.eggemann@arm.com, bsegall@google.com, mgorman@suse.de, vschneid@redhat.com, kprateek.nayak@amd.com, mark.rutland@arm.com, Dave.Martin@arm.com, james.morse@arm.com, babu.moger@amd.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org, rcu@vger.kernel.org, linux-trace-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-security-module@vger.kernel.org Subject: Re: [PATCH v2 1/8] sched: introduce for_each_process_rculock and for_each_thread_rculock Message-ID: References: <20260907081334.1152889-1-ye.liu@linux.dev> <20260907081334.1152889-2-ye.liu@linux.dev> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260907081334.1152889-2-ye.liu@linux.dev> X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: A18C814000C X-Stat-Signature: hwcjsfpy5jxuy66q1u6fyi67rdiazhbh X-Rspam-User: X-HE-Tag: 1788769861-842141 X-HE-Meta: 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 jJwaiSPj Yha0DU+rgazLw247nDXv54/Pq02uk7mXAecsWZaw8iHjwb/0PlNfZHgPpRxnIUNTN+B9etH18AM3SPfNpW3nTQzvrJL2edv8D9F+IYXKPJja5Ngk9ETN1y7mfIjKNuf27+SJcKXeJgg9AKxTA9OoAw/psy7B1BCBRWR1YnzpIPIvB8heSZCW4M1FI2c5ZXcm4YHKa9D92Fcl9+Hr3iA/PNdZ+NAlkUA8TTd4VHxyz/CmCR5WNsFcuaMTDJpv15IhM6WMIkHSS1DS9LXmD2SZ5hTe5FF77+r07RqZd23nCJSEEacx2X8TRieU+WQYwVcCkio8VHjHRKeTCQRIrFGeCgL6bXCxylQh7fVC5emknqeNXk+nGSUTcfJGhqbFg00HB8BVr6gBTlIuq30x99Cwp3zppjjfC9H7kbcXItC6tO5prsME8tPq6cxcjHB6CC+xM4ohFXUOibazX23U= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Mon, Sep 07, 2026 at 04:13:27PM +0800, Ye Liu wrote: > From: Ye Liu > > Introduce for_each_process_rculock(), for_each_thread_rculock() and > for_each_process_thread_rculock() macros that acquire the RCU read > lock before the iteration starts and release it when the loop is left, > so that the RCU read-side critical section is scoped to the loop body > instead of an externally managed rcu_read_lock()/rcu_read_unlock() > pair. > > Signed-off-by: Ye Liu > Acked-by: Michal Hocko Some nits below, with those addressed, LGTM so: Reviewed-by: Lorenzo Stoakes (ARM) > --- > Changes in v2: > - Rename macros from *_rcu to *_rculock (Steven Rostedt, Thomas Gleixner) > - Improve comment on for_each_process_thread_rculock() double loop > - Change prefix from mm: to sched: (Michal Hocko) > include/linux/sched/signal.h | 25 +++++++++++++++++++++++++ > 1 file changed, 25 insertions(+) > > diff --git a/include/linux/sched/signal.h b/include/linux/sched/signal.h > index 584ae88b435e..110ea9f131f3 100644 > --- a/include/linux/sched/signal.h > +++ b/include/linux/sched/signal.h > @@ -2,6 +2,7 @@ > #ifndef _LINUX_SCHED_SIGNAL_H > #define _LINUX_SCHED_SIGNAL_H > > +#include > #include > #include > #include > @@ -663,6 +664,30 @@ extern bool current_is_single_threaded(void); > #define for_each_process_thread(p, t) \ > for_each_process(p) for_each_thread(p, t) > > +/* > + * Variants of for_each_process(), for_each_thread() and > + * for_each_process_thread() that automatically acquire and release the > + * RCU read lock via scoped_guard(rcu). The lock is held for the > + * duration of the loop and released on exit, including via break, > + * goto, or return. > + */ > +#define for_each_process_rculock(p) \ > + scoped_guard(rcu) \ > + for (p = &init_task ; (p = next_task(p)) != &init_task ; ) NIT: Can you indent the for loop by a tab? Since the for is in scoped_guard() scope and that's not made clear. > + > +#define for_each_thread_rculock(p, t) \ > + scoped_guard(rcu) \ > + __for_each_thread((p)->signal, t) Same comment as above. > + > +/* > + * Double loop: 'break' only exits the inner for_each_thread() loop. > + * Use 'goto' to exit both loops; the RCU read lock is released > + * automatically when the scoped_guard scope is left. > + */ > +#define for_each_process_thread_rculock(p, t) \ > + scoped_guard(rcu) \ > + for_each_process(p) for_each_thread(p, t) Yeah this is even worse for clarity :) I know the existing defines do itg this way but it's kinda confusing. I know it's a bit fugly, but it's MUCH clearer as: #define for_each_process_thread_rculock(p, t) \ scoped_guard(rcu) \ for_each_process(p) \ for_each_thread(p, t) > + > typedef int (*proc_visitor)(struct task_struct *p, void *data); > void walk_process_tree(struct task_struct *top, proc_visitor, void *); > > -- > 2.25.1 > -- Cheers, Lorenzo