From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id C8A6BC79FA0 for ; Mon, 7 Sep 2026 12:21:11 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id E13F86B009E; Mon, 7 Sep 2026 08:21:10 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id DEB946B009F; Mon, 7 Sep 2026 08:21:10 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id D28696B00A0; Mon, 7 Sep 2026 08:21:10 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0017.hostedemail.com [216.40.44.17]) by kanga.kvack.org (Postfix) with ESMTP id AD0966B009E for ; Mon, 7 Sep 2026 08:21:10 -0400 (EDT) Received: from smtpin14.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay07.hostedemail.com (Postfix) with ESMTP id 4C21416013C for ; Mon, 7 Sep 2026 12:21:10 +0000 (UTC) X-FDA: 85186875900.14.1D33A9B Received: from tor.source.kernel.org (tor.source.kernel.org [172.105.4.254]) by imf31.hostedemail.com (Postfix) with ESMTP id 89E342000C for ; Mon, 7 Sep 2026 12:21:08 +0000 (UTC) Authentication-Results: imf31.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=bHCkg4gb; dmarc=pass (policy=quarantine) header.from=kernel.org; spf=pass (imf31.hostedemail.com: domain of ljs@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=ljs@kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1788783668; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=6RafqFe1zOQfVX4I3+CvQ7y72wqiedDGCRPziRNypvU=; b=cVxISRu7Fl9jcs/nfHKcK90ySx25TS1F6RSpxMYWW9+SxsoZK9jW9/PGlCRWwqT6rXqsVV nlDqMx1qiwY76ybX2nbKI5cmoxqNJRwTqGaHyXgn/zthYYP0/SaDsYytJQHw/QvSjKoVXc nEWYkIeG09msrB5nwlzl5yrngJTdBv4= ARC-Authentication-Results: i=1; imf31.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=bHCkg4gb; dmarc=pass (policy=quarantine) header.from=kernel.org; spf=pass (imf31.hostedemail.com: domain of ljs@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=ljs@kernel.org ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1788783668; b=G52lpMiV9lHkg7mKXOS7g0YZJ/QvsXvHdSFBMbv7JU6gGKfSEP4HairPX18R8PaV1E9OWE 2JMemC2/TIYcAIAIQhkq6a2hqdN1qbnLWHbuRWcvtRJKO0FX3ql8mBVBZBaFN/i/l0sST4 es2cr0rm59Of8ElGyajX4pNi637FElM= Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by tor.source.kernel.org (Postfix) with ESMTP id 013ED60AB5; Mon, 7 Sep 2026 12:21:08 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id A71C81F00A3A; Mon, 7 Sep 2026 12:20:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1788783667; bh=6RafqFe1zOQfVX4I3+CvQ7y72wqiedDGCRPziRNypvU=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=bHCkg4gbtV4fR2YXJbmLmuc4792CiiwMkkiRBQHsBe3wK55pXp+8DhreyLDcaIbMw +XMz1qywEjymPY3Ej4XpuBzolt+eJO+nukbZ7CXCsQNU26wwPA1iXIhTSrRLpbGDix fwWR2FArhe/UEy7m95AYiCBVgXqtLK4g9V7jnUSj20xaBegsmmoK4Eg5QF6p25qKod FvDJ/mDhse/p+LJ4rbaxHYb1QC5RLLos4JcnAt7VH2IvwsAiCyGi4lzj9mRyvxW/JA h+bvh9R1HO3HUjIq8DKQveOiIQHs0vc3Dpq6Hwle2VPzfsPQD/3qCXSkt6Tz4Wm3Zg Y31OxqU9Ezkow== Date: Mon, 7 Sep 2026 13:20:51 +0100 From: "Lorenzo Stoakes (ARM)" To: Ye Liu Cc: Thomas Gleixner , Peter Zijlstra , "Rafael J. Wysocki" , Andrew Morton , Ingo Molnar , Will Deacon , Boqun Feng , "Paul E. McKenney" , Frederic Weisbecker , Neeraj Upadhyay , Joel Fernandes , Josh Triplett , Uladzislau Rezki , Juri Lelli , Vincent Guittot , Steven Rostedt , Masami Hiramatsu , Josh Poimboeuf , Ye Liu , Michal Hocko , mic@digikod.net, oleg@redhat.com, david@kernel.org, linmiaohe@huawei.com, nao.horiguchi@gmail.com, gnoack3000@gmail.com, sj@kernel.org, rientjes@google.com, shakeel.butt@linux.dev, xu.xin16@zte.com.cn, chengming.zhou@linux.dev, 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, 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 5/8] kernel: convert process/thread iterators to for_each_*_rculock Message-ID: References: <20260907081334.1152889-1-ye.liu@linux.dev> <20260907081334.1152889-6-ye.liu@linux.dev> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20260907081334.1152889-6-ye.liu@linux.dev> X-Rspamd-Server: rspam11 X-Rspam-User: X-Stat-Signature: um185dgbh7pmziozw16rau67b7kfptqk X-Rspamd-Queue-Id: 89E342000C X-HE-Tag: 1788783668-736314 X-HE-Meta: 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 EtL+hzrK yx1LRJEtGyYE1wlMNCyj0JaXPAAK1MaqNFh/bd3+IST0yNKzyc5lN/sDHDyH5ML8/wW45vIZJojdqHIiHxwtM6z9bIwr6gdpUCjHllbetP3F3K5Bd27T/vyfZkpMePSgWuCVcibiGeAwnCOT/NR68IyChXo7DPUDYuF8d0RDheZVhoS/BMGII8UqAldKfgmUegQZgzZqYguxjDinCP0z+mnvfA8pmM2jllsrNUgk7hx4/2UmL3tbbMTLDFm55FfaUGjjIUa/ed5d55fnQV8l8PjBKLs6qEbaBKICq5IeH7rVqZwp50tgKb4E5wXXDtgBFVsZy995HZ8gV46Nn0fa3mucrjYfbZr0jM5nncXyRqyYXKf6o0gG9W2vG4VEME6ZUTE3Pl+2vY4F+/nlJ9M1sfXJ2KGm28wNgvRUYBkCwUBFvIScfd+rFXmY/C1PhuAhHw7bT3mTpTWCzBLlSwNDOXOGXVmsh7SUUsddY 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 04:13:31PM +0800, Ye Liu wrote: > From: Ye Liu > > Replace the manual rcu_read_lock()/rcu_read_unlock() and guard(rcu) > pairs combined with for_each_process(), for_each_thread() and > for_each_process_thread() loops across kernel/ with the > for_each_*_rculock() macros, which scope the RCU read lock to the > loop body via scoped_guard(rcu). > > No functional change. > > Signed-off-by: Ye Liu > Acked-by: Michal Hocko LGTM so: Reviewed-by: Lorenzo Stoakes (ARM) > --- > Changes in v2: > - Rename *_rcu to *_rculock > - Rename stale 'unlock:' label to 'out:' in hung_task.c (Günther Noack) > kernel/cpu.c | 4 +--- > kernel/freezer.c | 4 +--- > kernel/hung_task.c | 11 ++++------- > kernel/locking/lockdep.c | 4 +--- > kernel/rcu/update.c | 4 +--- > kernel/sched/core.c | 3 +-- > kernel/sched/debug.c | 4 +--- > kernel/trace/fgraph.c | 8 ++------ > kernel/unwind/deferred.c | 3 +-- > 9 files changed, 13 insertions(+), 32 deletions(-) > > diff --git a/kernel/cpu.c b/kernel/cpu.c > index b3c8553d7bd6..00638d2abc0f 100644 > --- a/kernel/cpu.c > +++ b/kernel/cpu.c > @@ -1254,8 +1254,7 @@ void clear_tasks_mm_cpumask(int cpu) > * full-fledged tasklist_lock. > */ > WARN_ON(cpu_online(cpu)); > - rcu_read_lock(); > - for_each_process(p) { > + for_each_process_rculock(p) { > struct task_struct *t; > > /* > @@ -1268,7 +1267,6 @@ void clear_tasks_mm_cpumask(int cpu) > arch_clear_mm_cpumask_cpu(cpu, t->mm); > task_unlock(t); > } > - rcu_read_unlock(); > } > > /* Take this CPU down. */ > diff --git a/kernel/freezer.c b/kernel/freezer.c > index a76bf957fb32..7a870f71dcf6 100644 > --- a/kernel/freezer.c > +++ b/kernel/freezer.c > @@ -217,11 +217,9 @@ void thaw_process(struct task_struct *p) > { > struct task_struct *t; > > - rcu_read_lock(); > - for_each_thread(p, t) { > + for_each_thread_rculock(p, t) { > __thaw_task(t); > } > - rcu_read_unlock(); > } > > /** > diff --git a/kernel/hung_task.c b/kernel/hung_task.c > index 6fcc94ce4ca9..73a5ad3be9a8 100644 > --- a/kernel/hung_task.c > +++ b/kernel/hung_task.c > @@ -315,13 +315,12 @@ static void check_hung_uninterruptible_tasks(unsigned long timeout) > return; > > this_round_count = 0; > - rcu_read_lock(); > - for_each_process_thread(g, t) { > + for_each_process_thread_rculock(g, t) { > if (!max_count--) > - goto unlock; > + goto out; > if (time_after(jiffies, last_break + HUNG_TASK_LOCK_BREAK)) { > if (!rcu_lock_break(g, t)) > - goto unlock; > + goto out; > last_break = jiffies; > } > > @@ -337,9 +336,7 @@ static void check_hung_uninterruptible_tasks(unsigned long timeout) > hung_task_info(t, timeout, this_round_count); > } > } > - unlock: > - rcu_read_unlock(); > - > +out: > if (!this_round_count) > return; > > diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c > index c56a7f91d72e..ea218dc75ad5 100644 > --- a/kernel/locking/lockdep.c > +++ b/kernel/locking/lockdep.c > @@ -6834,15 +6834,13 @@ void debug_show_all_locks(void) > } > pr_warn("\nShowing all locks held in the system:\n"); > > - rcu_read_lock(); > - for_each_process_thread(g, p) { > + for_each_process_thread_rculock(g, p) { > if (!p->lockdep_depth) > continue; > lockdep_print_held_locks(p); > touch_nmi_watchdog(); > touch_all_softlockup_watchdogs(); > } > - rcu_read_unlock(); > > pr_warn("\n"); > pr_warn("=============================================\n\n"); > diff --git a/kernel/rcu/update.c b/kernel/rcu/update.c > index 2a778b8ab4ad..d8e0b5896db9 100644 > --- a/kernel/rcu/update.c > +++ b/kernel/rcu/update.c > @@ -548,15 +548,13 @@ void synchronize_rcu_trivial_preempt(void) > struct task_struct *t; > > smp_mb(); // Order prior accesses before grace-period start. > - rcu_read_lock(); // Protect task list. > - for_each_process_thread(g, t) { > + for_each_process_thread_rculock(g, t) { > if (t == current) > continue; // Don't deadlock on ourselves! > // Order later rcu_read_lock() on other tasks after QS. > while (smp_load_acquire(&t->rcu_trivial_preempt_nesting)) > continue; > } > - rcu_read_unlock(); > } > EXPORT_SYMBOL_GPL(synchronize_rcu_trivial_preempt); > #endif // #if IS_ENABLED(CONFIG_TRIVIAL_PREEMPT_RCU) > diff --git a/kernel/sched/core.c b/kernel/sched/core.c > index 0697ed0f1c3d..fd5bdd2cb798 100644 > --- a/kernel/sched/core.c > +++ b/kernel/sched/core.c > @@ -2005,8 +2005,7 @@ static void uclamp_sync_util_min_rt_default(void) > smp_mb__after_spinlock(); > read_unlock(&tasklist_lock); > > - guard(rcu)(); > - for_each_process_thread(g, p) > + for_each_process_thread_rculock(g, p) > uclamp_update_util_min_rt_default(p); > } > > diff --git a/kernel/sched/debug.c b/kernel/sched/debug.c > index 72236db67983..cdae165b98f7 100644 > --- a/kernel/sched/debug.c > +++ b/kernel/sched/debug.c > @@ -1029,14 +1029,12 @@ static void print_rq(struct seq_file *m, struct rq *rq, int rq_cpu) > #endif > "\n"); > > - rcu_read_lock(); > - for_each_process_thread(g, p) { > + for_each_process_thread_rculock(g, p) { > if (task_cpu(p) != rq_cpu) > continue; > > print_task(m, rq, p); > } > - rcu_read_unlock(); > } > > void print_cfs_rq(struct seq_file *m, int cpu, struct cfs_rq *cfs_rq) > diff --git a/kernel/trace/fgraph.c b/kernel/trace/fgraph.c > index 40d373d65f9b..f797ce119223 100644 > --- a/kernel/trace/fgraph.c > +++ b/kernel/trace/fgraph.c > @@ -1057,11 +1057,10 @@ static int alloc_retstack_tasklist(unsigned long **ret_stack_list) > } > } > > - rcu_read_lock(); > - for_each_process_thread(g, t) { > + for_each_process_thread_rculock(g, t) { > if (start == end) { > ret = -EAGAIN; > - goto unlock; > + goto free; > } > > if (t->ret_stack == NULL) { > @@ -1074,9 +1073,6 @@ static int alloc_retstack_tasklist(unsigned long **ret_stack_list) > t->ret_stack = ret_stack_list[start++]; > } > } > - > -unlock: > - rcu_read_unlock(); > free: > for (i = start; i < end; i++) > kmem_cache_free(fgraph_stack_cachep, ret_stack_list[i]); > diff --git a/kernel/unwind/deferred.c b/kernel/unwind/deferred.c > index 5bea47314254..ecfe1336095e 100644 > --- a/kernel/unwind/deferred.c > +++ b/kernel/unwind/deferred.c > @@ -319,9 +319,8 @@ void unwind_deferred_cancel(struct unwind_work *work) > > synchronize_srcu(&unwind_srcu); > > - guard(rcu)(); > /* Clear this bit from all threads */ > - for_each_process_thread(g, t) { > + for_each_process_thread_rculock(g, t) { > atomic_long_andnot(BIT(bit), > &t->unwind_info.unwind_mask); > if (t->unwind_info.cache) > -- > 2.25.1 > -- Cheers, Lorenzo