linux-kernel - [PATCH 3/4] workqueue: add schedule_on_each

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Message-ID: <20230530145335.930262644@redhat.com>
Date:   Tue, 30 May 2023 11:52:37 -0300
From:   Marcelo Tosatti <mtosatti@...hat.com>
To:     Christoph Lameter <cl@...ux.com>
Cc:     Aaron Tomlin <atomlin@...mlin.com>,
        Frederic Weisbecker <frederic@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        Vlastimil Babka <vbabka@...e.cz>,
        Michal Hocko <mhocko@...e.com>,
        Marcelo Tosatti <mtosatti@...hat.com>
Subject: [PATCH 3/4] workqueue: add schedule_on_each_cpumask helper

Add a schedule_on_each_cpumask function, equivalent to
schedule_on_each_cpu but accepting a cpumask to operate.

Signed-off-by: Marcelo Tosatti <mtosatti@...hat.com>

---

Index: linux-vmstat-remote/kernel/workqueue.c
===================================================================
--- linux-vmstat-remote.orig/kernel/workqueue.c
+++ linux-vmstat-remote/kernel/workqueue.c
@@ -3455,6 +3455,56 @@ int schedule_on_each_cpu(work_func_t fun
 	return 0;
 }
 
+
+/**
+ * schedule_on_each_cpumask - execute a function synchronously on each
+ * CPU in "cpumask", for those which are online.
+ *
+ * @func: the function to call
+ * @mask: the CPUs which to call function on
+ *
+ * schedule_on_each_cpu() executes @func on each specified CPU that is online,
+ * using the system workqueue and blocks until all such CPUs have completed.
+ * schedule_on_each_cpu() is very slow.
+ *
+ * Return:
+ * 0 on success, -errno on failure.
+ */
+int schedule_on_each_cpumask(work_func_t func, cpumask_t *cpumask)
+{
+	int cpu;
+	struct work_struct __percpu *works;
+	cpumask_var_t effmask;
+
+	works = alloc_percpu(struct work_struct);
+	if (!works)
+		return -ENOMEM;
+
+	if (!alloc_cpumask_var(&effmask, GFP_KERNEL)) {
+		free_percpu(works);
+		return -ENOMEM;
+	}
+
+	cpumask_and(effmask, cpumask, cpu_online_mask);
+
+	cpus_read_lock();
+
+	for_each_cpu(cpu, effmask) {
+		struct work_struct *work = per_cpu_ptr(works, cpu);
+
+		INIT_WORK(work, func);
+		schedule_work_on(cpu, work);
+	}
+
+	for_each_cpu(cpu, effmask)
+		flush_work(per_cpu_ptr(works, cpu));
+
+	cpus_read_unlock();
+	free_percpu(works);
+	free_cpumask_var(effmask);
+	return 0;
+}
+
 /**
  * execute_in_process_context - reliably execute the routine with user context
  * @fn:		the function to execute
Index: linux-vmstat-remote/include/linux/workqueue.h
===================================================================
--- linux-vmstat-remote.orig/include/linux/workqueue.h
+++ linux-vmstat-remote/include/linux/workqueue.h
@@ -450,6 +450,7 @@ extern void __flush_workqueue(struct wor
 extern void drain_workqueue(struct workqueue_struct *wq);
 
 extern int schedule_on_each_cpu(work_func_t func);
+extern int schedule_on_each_cpumask(work_func_t func, cpumask_t *cpumask);
 
 int execute_in_process_context(work_func_t fn, struct execute_work *);