[PATCH v2 5/8] kernel: convert process/thread iterators to for_each_*_rculock
From: Ye Liu <hidden>
Date: 2026-09-07 08:14:55
Also in:
linux-fsdevel, linux-mm, linux-pm, linux-trace-kernel, lkml, rcu
Subsystem:
cpu hotplug, freezer, function hooks (ftrace), hung task detector, locking primitives, read-copy update (rcu), scheduler, the rest, tracing, userspace stack unwinding · Maintainers:
Thomas Gleixner, Peter Zijlstra, "Rafael J. Wysocki", Steven Rostedt, Masami Hiramatsu, Andrew Morton, Lance Yang, Ingo Molnar, Will Deacon, Boqun Feng, "Paul E. McKenney", Frederic Weisbecker, Neeraj Upadhyay, Joel Fernandes, Josh Triplett, Uladzislau Rezki, Juri Lelli, Vincent Guittot, Linus Torvalds, Josh Poimboeuf
From: Ye Liu <liuye@kylinos.cn> 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 <liuye@kylinos.cn> Acked-by: Michal Hocko <mhocko@suse.com> --- 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