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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>
This commit is contained in:
Paul E. McKenney 2021-11-08 16:52:02 -08:00
parent 9b073de1c7
commit 381a4f3b38
1 changed files with 20 additions and 22 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

42
kernel/rcu/tasks.h
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@ -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. */