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| author |   Paul E. McKenney <paulmck@kernel.org> | 2021-11-08 10:51:13 -0800 |
|---|---|---|
| committer | Paul E. McKenney <paulmck@kernel.org> | 2021-12-07 16:26:57 -0800 |
| commit | 7a30871b6a27de1a1f418c7fd2c5dde9a46bfd16 (patch) | |
| tree | c0b13f98b4f8ea2e44dbac97dae52c09d57222bb /kernel/rcu | |
| parent | rcu-tasks: Create per-CPU callback lists (diff) | |
| download | linux-dev-7a30871b6a27de1a1f418c7fd2c5dde9a46bfd16.tar.xz linux-dev-7a30871b6a27de1a1f418c7fd2c5dde9a46bfd16.zip | |
rcu-tasks: Introduce ->percpu_enqueue_shift for dynamic queue selection
This commit introduces a ->percpu_enqueue_shift field to the rcu_tasks
structure, and uses it to shift down the CPU number in order to
select a rcu_tasks_percpu structure. This field is currently set to a
sufficiently large shift count to always select the CPU-0 instance of
the rcu_tasks_percpu structure, and later commits will adjust this.
Reported-by: Martin Lau <kafai@fb.com>
Cc: Neeraj Upadhyay <neeraj.iitr10@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Diffstat (limited to 'kernel/rcu')
| -rw-r--r-- | kernel/rcu/tasks.h | 7 |
1 files changed, 6 insertions, 1 deletions
diff --git a/kernel/rcu/tasks.h b/kernel/rcu/tasks.h index 30048db7aa49..2a5fe3e04b36 100644 --- a/kernel/rcu/tasks.h +++ b/kernel/rcu/tasks.h @@ -52,6 +52,7 @@ struct rcu_tasks_percpu { * @postgp_func: This flavor's post-grace-period function (optional). * @call_func: This flavor's call_rcu()-equivalent function. * @rtpcpu: This flavor's rcu_tasks_percpu structure. + * @percpu_enqueue_shift: Shift down CPU ID this much when enqueuing callbacks. * @name: This flavor's textual name. * @kname: This flavor's kthread name. */ @@ -75,6 +76,7 @@ struct rcu_tasks { postgp_func_t postgp_func; call_rcu_func_t call_func; struct rcu_tasks_percpu __percpu *rtpcpu; + int percpu_enqueue_shift; char *name; char *kname; }; @@ -91,6 +93,7 @@ static struct rcu_tasks rt_name = \ .call_func = call, \ .rtpcpu = &rt_name ## __percpu, \ .name = n, \ + .percpu_enqueue_shift = ilog2(CONFIG_NR_CPUS), \ .kname = #rt_name, \ } @@ -169,6 +172,7 @@ static void cblist_init_generic(struct rcu_tasks *rtp) unsigned long flags; raw_spin_lock_irqsave(&rtp->cbs_gbl_lock, flags); + rtp->percpu_enqueue_shift = ilog2(nr_cpu_ids); for_each_possible_cpu(cpu) { struct rcu_tasks_percpu *rtpcp = per_cpu_ptr(rtp->rtpcpu, cpu); @@ -195,7 +199,8 @@ static void call_rcu_tasks_generic(struct rcu_head *rhp, rcu_callback_t func, rhp->next = NULL; rhp->func = func; local_irq_save(flags); - rtpcp = per_cpu_ptr(rtp->rtpcpu, 0 /* smp_processor_id() */); + rtpcp = per_cpu_ptr(rtp->rtpcpu, + smp_processor_id() >> READ_ONCE(rtp->percpu_enqueue_shift)); raw_spin_lock(&rtpcp->cbs_pcpu_lock); if (!rtpcp->cbs_tail) { raw_spin_unlock(&rtpcp->cbs_pcpu_lock); // irqs remain disabled. |