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Subject[patch V2 28/67] workqueue: Convert to state machine callbacks
From: Thomas Gleixner <tglx@linutronix.de>

Get rid of the prio ordering of the separate notifiers and use a proper state
callback pair.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Acked-by: Tejun Heo <tj@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Lai Jiangshan <jiangshanlai@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Nicolas Iooss <nicolas.iooss_linux@m4x.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Anna-Maria Gleixner <anna-maria@linutronix.de>
---
include/linux/cpu.h | 9 ---
include/linux/cpuhotplug.h | 2
include/linux/workqueue.h | 6 ++
kernel/cpu.c | 10 ++++
kernel/workqueue.c | 108 +++++++++++++++++----------------------------
5 files changed, 61 insertions(+), 74 deletions(-)

--- a/include/linux/cpu.h
+++ b/include/linux/cpu.h
@@ -55,15 +55,6 @@ extern ssize_t arch_cpu_release(const ch
#endif
struct notifier_block;

-/*
- * CPU notifier priorities.
- */
-enum {
- /* bring up workqueues before normal notifiers and down after */
- CPU_PRI_WORKQUEUE_UP = 5,
- CPU_PRI_WORKQUEUE_DOWN = -5,
-};
-
#define CPU_ONLINE 0x0002 /* CPU (unsigned)v is up */
#define CPU_UP_PREPARE 0x0003 /* CPU (unsigned)v coming up */
#define CPU_UP_CANCELED 0x0004 /* CPU (unsigned)v NOT coming up */
--- a/include/linux/cpuhotplug.h
+++ b/include/linux/cpuhotplug.h
@@ -12,6 +12,7 @@ enum cpuhp_state {
CPUHP_PERF_BFIN,
CPUHP_PERF_POWER,
CPUHP_PERF_SUPERH,
+ CPUHP_WORKQUEUE_PREP,
CPUHP_NOTIFY_PREPARE,
CPUHP_BRINGUP_CPU,
CPUHP_AP_IDLE_DEAD,
@@ -49,6 +50,7 @@ enum cpuhp_state {
CPUHP_AP_PERF_S390_SF_ONLINE,
CPUHP_AP_PERF_ARM_CCI_ONLINE,
CPUHP_AP_PERF_ARM_CCN_ONLINE,
+ CPUHP_AP_WORKQUEUE_ONLINE,
CPUHP_AP_NOTIFY_ONLINE,
CPUHP_AP_ONLINE_DYN,
CPUHP_AP_ONLINE_DYN_END = CPUHP_AP_ONLINE_DYN + 30,
--- a/include/linux/workqueue.h
+++ b/include/linux/workqueue.h
@@ -625,4 +625,10 @@ void wq_watchdog_touch(int cpu);
static inline void wq_watchdog_touch(int cpu) { }
#endif /* CONFIG_WQ_WATCHDOG */

+#ifdef CONFIG_SMP
+int workqueue_prepare_cpu(unsigned int cpu);
+int workqueue_online_cpu(unsigned int cpu);
+int workqueue_offline_cpu(unsigned int cpu);
+#endif
+
#endif
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -1185,6 +1185,11 @@ static struct cpuhp_step cpuhp_bp_states
.startup = perf_event_init_cpu,
.teardown = perf_event_exit_cpu,
},
+ [CPUHP_WORKQUEUE_PREP] = {
+ .name = "workqueue prepare",
+ .startup = workqueue_prepare_cpu,
+ .teardown = NULL,
+ },
/*
* Preparatory and dead notifiers. Will be replaced once the notifiers
* are converted to states.
@@ -1265,6 +1270,11 @@ static struct cpuhp_step cpuhp_ap_states
.startup = perf_event_init_cpu,
.teardown = perf_event_exit_cpu,
},
+ [CPUHP_AP_WORKQUEUE_ONLINE] = {
+ .name = "workqueue online",
+ .startup = workqueue_online_cpu,
+ .teardown = workqueue_offline_cpu,
+ },

/*
* Online/down_prepare notifiers. Will be removed once the notifiers
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -4611,84 +4611,65 @@ static void restore_unbound_workers_cpum
pool->attrs->cpumask) < 0);
}

-/*
- * Workqueues should be brought up before normal priority CPU notifiers.
- * This will be registered high priority CPU notifier.
- */
-static int workqueue_cpu_up_callback(struct notifier_block *nfb,
- unsigned long action,
- void *hcpu)
+int workqueue_prepare_cpu(unsigned int cpu)
+{
+ struct worker_pool *pool;
+
+ for_each_cpu_worker_pool(pool, cpu) {
+ if (pool->nr_workers)
+ continue;
+ if (!create_worker(pool))
+ return -ENOMEM;
+ }
+ return 0;
+}
+
+int workqueue_online_cpu(unsigned int cpu)
{
- int cpu = (unsigned long)hcpu;
struct worker_pool *pool;
struct workqueue_struct *wq;
int pi;

- switch (action & ~CPU_TASKS_FROZEN) {
- case CPU_UP_PREPARE:
- for_each_cpu_worker_pool(pool, cpu) {
- if (pool->nr_workers)
- continue;
- if (!create_worker(pool))
- return NOTIFY_BAD;
- }
- break;
-
- case CPU_DOWN_FAILED:
- case CPU_ONLINE:
- mutex_lock(&wq_pool_mutex);
+ mutex_lock(&wq_pool_mutex);

- for_each_pool(pool, pi) {
- mutex_lock(&pool->attach_mutex);
+ for_each_pool(pool, pi) {
+ mutex_lock(&pool->attach_mutex);

- if (pool->cpu == cpu)
- rebind_workers(pool);
- else if (pool->cpu < 0)
- restore_unbound_workers_cpumask(pool, cpu);
+ if (pool->cpu == cpu)
+ rebind_workers(pool);
+ else if (pool->cpu < 0)
+ restore_unbound_workers_cpumask(pool, cpu);

- mutex_unlock(&pool->attach_mutex);
- }
+ mutex_unlock(&pool->attach_mutex);
+ }

- /* update NUMA affinity of unbound workqueues */
- list_for_each_entry(wq, &workqueues, list)
- wq_update_unbound_numa(wq, cpu, true);
+ /* update NUMA affinity of unbound workqueues */
+ list_for_each_entry(wq, &workqueues, list)
+ wq_update_unbound_numa(wq, cpu, true);

- mutex_unlock(&wq_pool_mutex);
- break;
- }
- return NOTIFY_OK;
+ mutex_unlock(&wq_pool_mutex);
+ return 0;
}

-/*
- * Workqueues should be brought down after normal priority CPU notifiers.
- * This will be registered as low priority CPU notifier.
- */
-static int workqueue_cpu_down_callback(struct notifier_block *nfb,
- unsigned long action,
- void *hcpu)
+int workqueue_offline_cpu(unsigned int cpu)
{
- int cpu = (unsigned long)hcpu;
struct work_struct unbind_work;
struct workqueue_struct *wq;

- switch (action & ~CPU_TASKS_FROZEN) {
- case CPU_DOWN_PREPARE:
- /* unbinding per-cpu workers should happen on the local CPU */
- INIT_WORK_ONSTACK(&unbind_work, wq_unbind_fn);
- queue_work_on(cpu, system_highpri_wq, &unbind_work);
-
- /* update NUMA affinity of unbound workqueues */
- mutex_lock(&wq_pool_mutex);
- list_for_each_entry(wq, &workqueues, list)
- wq_update_unbound_numa(wq, cpu, false);
- mutex_unlock(&wq_pool_mutex);
-
- /* wait for per-cpu unbinding to finish */
- flush_work(&unbind_work);
- destroy_work_on_stack(&unbind_work);
- break;
- }
- return NOTIFY_OK;
+ /* unbinding per-cpu workers should happen on the local CPU */
+ INIT_WORK_ONSTACK(&unbind_work, wq_unbind_fn);
+ queue_work_on(cpu, system_highpri_wq, &unbind_work);
+
+ /* update NUMA affinity of unbound workqueues */
+ mutex_lock(&wq_pool_mutex);
+ list_for_each_entry(wq, &workqueues, list)
+ wq_update_unbound_numa(wq, cpu, false);
+ mutex_unlock(&wq_pool_mutex);
+
+ /* wait for per-cpu unbinding to finish */
+ flush_work(&unbind_work);
+ destroy_work_on_stack(&unbind_work);
+ return 0;
}

#ifdef CONFIG_SMP
@@ -5490,9 +5471,6 @@ static int __init init_workqueues(void)

pwq_cache = KMEM_CACHE(pool_workqueue, SLAB_PANIC);

- cpu_notifier(workqueue_cpu_up_callback, CPU_PRI_WORKQUEUE_UP);
- hotcpu_notifier(workqueue_cpu_down_callback, CPU_PRI_WORKQUEUE_DOWN);
-
wq_numa_init();

/* initialize CPU pools */

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