rcu-tasks: Use spin_lock_rcu_node() and friends

This commit renames the rcu_tasks_percpu structure's ->cbs_pcpu_lock
to ->lock and then uses spin_lock_rcu_node() and friends to acquire and
release this lock, preparing for upcoming commits that will spread the
grace-period process across multiple CPUs and kthreads.

[ paulmck: Apply feedback from kernel test robot. ]

Reported-by: Martin Lau <kafai@fb.com>
Cc: Neeraj Upadhyay <neeraj.iitr10@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

diff --git a/kernel/rcu/tasks.h b/kernel/rcu/tasks.h
index 2e58d7fa2da41310f8c3822afe67de23eb9530cd..8cf325146fb096204b99abea64030d642ec5a1c7 100644 (file)
--- a/kernel/rcu/tasks.h
+++ b/kernel/rcu/tasks.h
@@ -23,11 +23,11 @@ typedef void (*postgp_func_t)(struct rcu_tasks *rtp);
 /**
  * struct rcu_tasks_percpu - Per-CPU component of definition for a Tasks-RCU-like mechanism.
  * @cblist: Callback list.
- * @cbs_pcpu_lock: Lock protecting per-CPU callback list.
+ * @lock: Lock protecting per-CPU callback list.
  */
 struct rcu_tasks_percpu {
        struct rcu_segcblist cblist;
-       raw_spinlock_t cbs_pcpu_lock;
+       raw_spinlock_t __private lock;
 };
 
 /**
@@ -82,7 +82,7 @@ struct rcu_tasks {
 
 #define DEFINE_RCU_TASKS(rt_name, gp, call, n)                                         \
 static DEFINE_PER_CPU(struct rcu_tasks_percpu, rt_name ## __percpu) = {                        \
-       .cbs_pcpu_lock = __RAW_SPIN_LOCK_UNLOCKED(rt_name ## __percpu.cbs_pcpu_lock),   \
+       .lock = __RAW_SPIN_LOCK_UNLOCKED(rt_name ## __percpu.cbs_pcpu_lock),            \
 };                                                                                     \
 static struct rcu_tasks rt_name =                                                      \
 {                                                                                      \
@@ -177,11 +177,11 @@ static void cblist_init_generic(struct rcu_tasks *rtp)
 
                WARN_ON_ONCE(!rtpcp);
                if (cpu)
-                       raw_spin_lock_init(&rtpcp->cbs_pcpu_lock);
-               raw_spin_lock(&rtpcp->cbs_pcpu_lock); // irqs already disabled.
+                       raw_spin_lock_init(&ACCESS_PRIVATE(rtpcp, lock));
+               raw_spin_lock_rcu_node(rtpcp); // irqs already disabled.
                if (rcu_segcblist_empty(&rtpcp->cblist))
                        rcu_segcblist_init(&rtpcp->cblist);
-               raw_spin_unlock(&rtpcp->cbs_pcpu_lock); // irqs remain disabled.
+               raw_spin_unlock_rcu_node(rtpcp); // irqs remain disabled.
        }
        raw_spin_unlock_irqrestore(&rtp->cbs_gbl_lock, flags);
 
@@ -200,15 +200,15 @@ static void call_rcu_tasks_generic(struct rcu_head *rhp, rcu_callback_t func,
        local_irq_save(flags);
        rtpcp = per_cpu_ptr(rtp->rtpcpu,
                            smp_processor_id() >> READ_ONCE(rtp->percpu_enqueue_shift));
-       raw_spin_lock(&rtpcp->cbs_pcpu_lock);
+       raw_spin_lock_rcu_node(rtpcp); // irqs already disabled.
        if (!rcu_segcblist_is_enabled(&rtpcp->cblist)) {
-               raw_spin_unlock(&rtpcp->cbs_pcpu_lock); // irqs remain disabled.
+               raw_spin_unlock_rcu_node(rtpcp); // irqs remain disabled.
                cblist_init_generic(rtp);
-               raw_spin_lock(&rtpcp->cbs_pcpu_lock); // irqs already disabled.
+               raw_spin_lock_rcu_node(rtpcp); // irqs already disabled.
        }
        needwake = rcu_segcblist_empty(&rtpcp->cblist);
        rcu_segcblist_enqueue(&rtpcp->cblist, rhp);
-       raw_spin_unlock_irqrestore(&rtpcp->cbs_pcpu_lock, flags);
+       raw_spin_unlock_irqrestore_rcu_node(rtpcp, flags);
        /* We can't create the thread unless interrupts are enabled. */
        if (needwake && READ_ONCE(rtp->kthread_ptr))
                wake_up(&rtp->cbs_wq);
@@ -250,11 +250,10 @@ static int __noreturn rcu_tasks_kthread(void *arg)
                set_tasks_gp_state(rtp, RTGS_WAIT_CBS);
 
                /* Pick up any new callbacks. */
-               raw_spin_lock_irqsave(&rtpcp->cbs_pcpu_lock, flags);
-               smp_mb__after_spinlock(); // Order updates vs. GP.
+               raw_spin_lock_irqsave_rcu_node(rtpcp, flags);
                rcu_segcblist_advance(&rtpcp->cblist, rcu_seq_current(&rtp->tasks_gp_seq));
                (void)rcu_segcblist_accelerate(&rtpcp->cblist, rcu_seq_snap(&rtp->tasks_gp_seq));
-               raw_spin_unlock_irqrestore(&rtpcp->cbs_pcpu_lock, flags);
+               raw_spin_unlock_irqrestore_rcu_node(rtpcp, flags);
 
                /* If there were none, wait a bit and start over. */
                if (!rcu_segcblist_pend_cbs(&rtpcp->cblist)) {
@@ -277,11 +276,10 @@ static int __noreturn rcu_tasks_kthread(void *arg)
 
                /* Invoke the callbacks. */
                set_tasks_gp_state(rtp, RTGS_INVOKE_CBS);
-               raw_spin_lock_irqsave(&rtpcp->cbs_pcpu_lock, flags);
-               smp_mb__after_spinlock(); // Order updates vs. GP.
+               raw_spin_lock_irqsave_rcu_node(rtpcp, flags);
                rcu_segcblist_advance(&rtpcp->cblist, rcu_seq_current(&rtp->tasks_gp_seq));
                rcu_segcblist_extract_done_cbs(&rtpcp->cblist, &rcl);
-               raw_spin_unlock_irqrestore(&rtpcp->cbs_pcpu_lock, flags);
+               raw_spin_unlock_irqrestore_rcu_node(rtpcp, flags);
                len = rcl.len;
                for (rhp = rcu_cblist_dequeue(&rcl); rhp; rhp = rcu_cblist_dequeue(&rcl)) {
                        local_bh_disable();
@@ -289,10 +287,10 @@ static int __noreturn rcu_tasks_kthread(void *arg)
                        local_bh_enable();
                        cond_resched();
                }
-               raw_spin_lock_irqsave(&rtpcp->cbs_pcpu_lock, flags);
+               raw_spin_lock_irqsave_rcu_node(rtpcp, flags);
                rcu_segcblist_add_len(&rtpcp->cblist, -len);
                (void)rcu_segcblist_accelerate(&rtpcp->cblist, rcu_seq_snap(&rtp->tasks_gp_seq));
-               raw_spin_unlock_irqrestore(&rtpcp->cbs_pcpu_lock, flags);
+               raw_spin_unlock_irqrestore_rcu_node(rtpcp, flags);
                /* Paranoid sleep to keep this from entering a tight loop */
                schedule_timeout_idle(rtp->gp_sleep);
        }
@@ -470,10 +468,10 @@ static void rcu_tasks_wait_gp(struct rcu_tasks *rtp)
 // exit_tasks_rcu_finish() functions begin and end, respectively, the SRCU
 // read-side critical sections waited for by rcu_tasks_postscan().
 //
-// Pre-grace-period update-side code is ordered before the grace via the
-// ->cbs_lock and the smp_mb__after_spinlock().  Pre-grace-period read-side
-// code is ordered before the grace period via synchronize_rcu() call
-// in rcu_tasks_pregp_step() and by the scheduler's locks and interrupt
+// Pre-grace-period update-side code is ordered before the grace
+// via the raw_spin_lock.*rcu_node().  Pre-grace-period read-side code
+// is ordered before the grace period via synchronize_rcu() call in
+// rcu_tasks_pregp_step() and by the scheduler's locks and interrupt
 // disabling.
 
 /* Pre-grace-period preparation. */