if (nr_cpu_ids != NR_CPUS)
printk(KERN_INFO "\tRCU restricting CPUs from NR_CPUS=%d to nr_cpu_ids=%d.\n", NR_CPUS, nr_cpu_ids);
#ifdef CONFIG_RCU_NOCB_CPU
+#ifndef CONFIG_RCU_NOCB_CPU_NONE
+ if (!have_rcu_nocb_mask) {
+ alloc_bootmem_cpumask_var(&rcu_nocb_mask);
+ have_rcu_nocb_mask = true;
+ }
+#ifdef CONFIG_RCU_NOCB_CPU_ZERO
+ pr_info("\tExperimental no-CBs CPU 0\n");
+ cpumask_set_cpu(0, rcu_nocb_mask);
+#endif /* #ifdef CONFIG_RCU_NOCB_CPU_ZERO */
+#ifdef CONFIG_RCU_NOCB_CPU_ALL
+ pr_info("\tExperimental no-CBs for all CPUs\n");
+ cpumask_setall(rcu_nocb_mask);
+#endif /* #ifdef CONFIG_RCU_NOCB_CPU_ALL */
+#endif /* #ifndef CONFIG_RCU_NOCB_CPU_NONE */
if (have_rcu_nocb_mask) {
- if (cpumask_test_cpu(0, rcu_nocb_mask)) {
- cpumask_clear_cpu(0, rcu_nocb_mask);
- pr_info("\tCPU 0: illegal no-CBs CPU (cleared).\n");
- }
cpulist_scnprintf(nocb_buf, sizeof(nocb_buf), rcu_nocb_mask);
pr_info("\tExperimental no-CBs CPUs: %s.\n", nocb_buf);
if (rcu_nocb_poll)
#ifdef CONFIG_TREE_PREEMPT_RCU
struct rcu_state rcu_preempt_state =
- RCU_STATE_INITIALIZER(rcu_preempt, call_rcu);
+ RCU_STATE_INITIALIZER(rcu_preempt, 'p', call_rcu);
DEFINE_PER_CPU(struct rcu_data, rcu_preempt_data);
static struct rcu_state *rcu_state = &rcu_preempt_state;
}
early_param("rcu_nocb_poll", parse_rcu_nocb_poll);
+/*
+ * Do any no-CBs CPUs need another grace period?
+ *
+ * Interrupts must be disabled. If the caller does not hold the root
+ * rnp_node structure's ->lock, the results are advisory only.
+ */
+static int rcu_nocb_needs_gp(struct rcu_state *rsp)
+{
+ struct rcu_node *rnp = rcu_get_root(rsp);
+
+ return rnp->n_nocb_gp_requests[(ACCESS_ONCE(rnp->completed) + 1) & 0x1];
+}
+
+/*
+ * Clean up this rcu_node structure's no-CBs state at the end of
+ * a grace period, and also return whether any no-CBs CPU associated
+ * with this rcu_node structure needs another grace period.
+ */
+static int rcu_nocb_gp_cleanup(struct rcu_state *rsp, struct rcu_node *rnp)
+{
+ int c = rnp->completed;
+ int needmore;
+
+ wake_up_all(&rnp->nocb_gp_wq[c & 0x1]);
+ rnp->n_nocb_gp_requests[c & 0x1] = 0;
+ needmore = rnp->n_nocb_gp_requests[(c + 1) & 0x1];
+ trace_rcu_nocb_grace_period(rsp->name, rnp->gpnum, rnp->completed,
+ c, rnp->level, rnp->grplo, rnp->grphi,
+ needmore ? "CleanupMore" : "Cleanup");
+ return needmore;
+}
+
+/*
+ * Set the root rcu_node structure's ->n_nocb_gp_requests field
+ * based on the sum of those of all rcu_node structures. This does
+ * double-count the root rcu_node structure's requests, but this
+ * is necessary to handle the possibility of a rcu_nocb_kthread()
+ * having awakened during the time that the rcu_node structures
+ * were being updated for the end of the previous grace period.
+ */
+static void rcu_nocb_gp_set(struct rcu_node *rnp, int nrq)
+{
+ rnp->n_nocb_gp_requests[(rnp->completed + 1) & 0x1] += nrq;
+}
+
+static void rcu_init_one_nocb(struct rcu_node *rnp)
+{
+ init_waitqueue_head(&rnp->nocb_gp_wq[0]);
+ init_waitqueue_head(&rnp->nocb_gp_wq[1]);
+}
+
/* Is the specified CPU a no-CPUs CPU? */
static bool is_nocb_cpu(int cpu)
{
if (!is_nocb_cpu(rdp->cpu))
return 0;
__call_rcu_nocb_enqueue(rdp, rhp, &rhp->next, 1, lazy);
+ if (__is_kfree_rcu_offset((unsigned long)rhp->func))
+ trace_rcu_kfree_callback(rdp->rsp->name, rhp,
+ (unsigned long)rhp->func,
+ rdp->qlen_lazy, rdp->qlen);
+ else
+ trace_rcu_callback(rdp->rsp->name, rhp,
+ rdp->qlen_lazy, rdp->qlen);
return 1;
}
}
/*
- * There must be at least one non-no-CBs CPU in operation at any given
- * time, because no-CBs CPUs are not capable of initiating grace periods
- * independently. This function therefore complains if the specified
- * CPU is the last non-no-CBs CPU, allowing the CPU-hotplug system to
- * avoid offlining the last such CPU. (Recursion is a wonderful thing,
- * but you have to have a base case!)
+ * If necessary, kick off a new grace period, and either way wait
+ * for a subsequent grace period to complete.
*/
-static bool nocb_cpu_expendable(int cpu)
+static void rcu_nocb_wait_gp(struct rcu_data *rdp)
{
- cpumask_var_t non_nocb_cpus;
- int ret;
+ unsigned long c;
+ bool d;
+ unsigned long flags;
+ unsigned long flags1;
+ struct rcu_node *rnp = rdp->mynode;
+ struct rcu_node *rnp_root = rcu_get_root(rdp->rsp);
- /*
- * If there are no no-CB CPUs or if this CPU is not a no-CB CPU,
- * then offlining this CPU is harmless. Let it happen.
- */
- if (!have_rcu_nocb_mask || is_nocb_cpu(cpu))
- return 1;
+ raw_spin_lock_irqsave(&rnp->lock, flags);
+ c = rnp->completed + 2;
- /* If no memory, play it safe and keep the CPU around. */
- if (!alloc_cpumask_var(&non_nocb_cpus, GFP_NOIO))
- return 0;
- cpumask_andnot(non_nocb_cpus, cpu_online_mask, rcu_nocb_mask);
- cpumask_clear_cpu(cpu, non_nocb_cpus);
- ret = !cpumask_empty(non_nocb_cpus);
- free_cpumask_var(non_nocb_cpus);
- return ret;
-}
+ /* Count our request for a grace period. */
+ rnp->n_nocb_gp_requests[c & 0x1]++;
+ trace_rcu_nocb_grace_period(rdp->rsp->name, rnp->gpnum, rnp->completed,
+ c, rnp->level, rnp->grplo, rnp->grphi,
+ "Startleaf");
-/*
- * Helper structure for remote registry of RCU callbacks.
- * This is needed for when a no-CBs CPU needs to start a grace period.
- * If it just invokes call_rcu(), the resulting callback will be queued,
- * which can result in deadlock.
- */
-struct rcu_head_remote {
- struct rcu_head *rhp;
- call_rcu_func_t *crf;
- void (*func)(struct rcu_head *rhp);
-};
+ if (rnp->gpnum != rnp->completed) {
-/*
- * Register a callback as specified by the rcu_head_remote struct.
- * This function is intended to be invoked via smp_call_function_single().
- */
-static void call_rcu_local(void *arg)
-{
- struct rcu_head_remote *rhrp =
- container_of(arg, struct rcu_head_remote, rhp);
+ /*
+ * This rcu_node structure believes that a grace period
+ * is in progress, so we are done. When this grace
+ * period ends, our request will be acted upon.
+ */
+ trace_rcu_nocb_grace_period(rdp->rsp->name,
+ rnp->gpnum, rnp->completed, c,
+ rnp->level, rnp->grplo, rnp->grphi,
+ "Startedleaf");
+ raw_spin_unlock_irqrestore(&rnp->lock, flags);
- rhrp->crf(rhrp->rhp, rhrp->func);
-}
+ } else {
-/*
- * Set up an rcu_head_remote structure and the invoke call_rcu_local()
- * on CPU 0 (which is guaranteed to be a non-no-CBs CPU) via
- * smp_call_function_single().
- */
-static void invoke_crf_remote(struct rcu_head *rhp,
- void (*func)(struct rcu_head *rhp),
- call_rcu_func_t crf)
-{
- struct rcu_head_remote rhr;
+ /*
+ * Might not be a grace period, check root rcu_node
+ * structure to see if we must start one.
+ */
+ if (rnp != rnp_root)
+ raw_spin_lock(&rnp_root->lock); /* irqs disabled. */
+ if (rnp_root->gpnum != rnp_root->completed) {
+ trace_rcu_nocb_grace_period(rdp->rsp->name,
+ rnp->gpnum, rnp->completed,
+ c, rnp->level,
+ rnp->grplo, rnp->grphi,
+ "Startedleafroot");
+ raw_spin_unlock(&rnp_root->lock); /* irqs disabled. */
+ } else {
- rhr.rhp = rhp;
- rhr.crf = crf;
- rhr.func = func;
- smp_call_function_single(0, call_rcu_local, &rhr, 1);
-}
+ /*
+ * No grace period, so we need to start one.
+ * The good news is that we can wait for exactly
+ * one grace period instead of part of the current
+ * grace period and all of the next grace period.
+ * Adjust counters accordingly and start the
+ * needed grace period.
+ */
+ rnp->n_nocb_gp_requests[c & 0x1]--;
+ c = rnp_root->completed + 1;
+ rnp->n_nocb_gp_requests[c & 0x1]++;
+ rnp_root->n_nocb_gp_requests[c & 0x1]++;
+ trace_rcu_nocb_grace_period(rdp->rsp->name,
+ rnp->gpnum, rnp->completed,
+ c, rnp->level,
+ rnp->grplo, rnp->grphi,
+ "Startedroot");
+ local_save_flags(flags1);
+ rcu_start_gp(rdp->rsp, flags1); /* Rlses ->lock. */
+ }
-/*
- * Helper functions to be passed to wait_rcu_gp(), each of which
- * invokes invoke_crf_remote() to register a callback appropriately.
- */
-static void __maybe_unused
-call_rcu_preempt_remote(struct rcu_head *rhp,
- void (*func)(struct rcu_head *rhp))
-{
- invoke_crf_remote(rhp, func, call_rcu);
-}
-static void call_rcu_bh_remote(struct rcu_head *rhp,
- void (*func)(struct rcu_head *rhp))
-{
- invoke_crf_remote(rhp, func, call_rcu_bh);
-}
-static void call_rcu_sched_remote(struct rcu_head *rhp,
- void (*func)(struct rcu_head *rhp))
-{
- invoke_crf_remote(rhp, func, call_rcu_sched);
+ /* Clean up locking and irq state. */
+ if (rnp != rnp_root)
+ raw_spin_unlock_irqrestore(&rnp->lock, flags);
+ else
+ local_irq_restore(flags);
+ }
+
+ /*
+ * Wait for the grace period. Do so interruptibly to avoid messing
+ * up the load average.
+ */
+ trace_rcu_nocb_grace_period(rdp->rsp->name, rnp->gpnum, rnp->completed,
+ c, rnp->level, rnp->grplo, rnp->grphi,
+ "StartWait");
+ for (;;) {
+ wait_event_interruptible(
+ rnp->nocb_gp_wq[c & 0x1],
+ (d = ULONG_CMP_GE(ACCESS_ONCE(rnp->completed), c)));
+ if (likely(d))
+ break;
+ flush_signals(current);
+ trace_rcu_nocb_grace_period(rdp->rsp->name,
+ rnp->gpnum, rnp->completed, c,
+ rnp->level, rnp->grplo, rnp->grphi,
+ "ResumeWait");
+ }
+ trace_rcu_nocb_grace_period(rdp->rsp->name, rnp->gpnum, rnp->completed,
+ c, rnp->level, rnp->grplo, rnp->grphi,
+ "EndWait");
+ smp_mb(); /* Ensure that CB invocation happens after GP end. */
}
/*
cl = atomic_long_xchg(&rdp->nocb_q_count_lazy, 0);
ACCESS_ONCE(rdp->nocb_p_count) += c;
ACCESS_ONCE(rdp->nocb_p_count_lazy) += cl;
- wait_rcu_gp(rdp->rsp->call_remote);
+ rcu_nocb_wait_gp(rdp);
/* Each pass through the following loop invokes a callback. */
trace_rcu_batch_start(rdp->rsp->name, cl, c, -1);
return;
for_each_cpu(cpu, rcu_nocb_mask) {
rdp = per_cpu_ptr(rsp->rda, cpu);
- t = kthread_run(rcu_nocb_kthread, rdp, "rcuo%d", cpu);
+ t = kthread_run(rcu_nocb_kthread, rdp,
+ "rcuo%c/%d", rsp->abbr, cpu);
BUG_ON(IS_ERR(t));
ACCESS_ONCE(rdp->nocb_kthread) = t;
}
}
/* Prevent __call_rcu() from enqueuing callbacks on no-CBs CPUs */
-static void init_nocb_callback_list(struct rcu_data *rdp)
+static bool init_nocb_callback_list(struct rcu_data *rdp)
{
if (rcu_nocb_mask == NULL ||
!cpumask_test_cpu(rdp->cpu, rcu_nocb_mask))
- return;
+ return false;
rdp->nxttail[RCU_NEXT_TAIL] = NULL;
+ return true;
}
-/* Initialize the ->call_remote fields in the rcu_state structures. */
-static void __init rcu_init_nocb(void)
+#else /* #ifdef CONFIG_RCU_NOCB_CPU */
+
+static int rcu_nocb_needs_gp(struct rcu_state *rsp)
{
-#ifdef CONFIG_PREEMPT_RCU
- rcu_preempt_state.call_remote = call_rcu_preempt_remote;
-#endif /* #ifdef CONFIG_PREEMPT_RCU */
- rcu_bh_state.call_remote = call_rcu_bh_remote;
- rcu_sched_state.call_remote = call_rcu_sched_remote;
+ return 0;
}
-#else /* #ifdef CONFIG_RCU_NOCB_CPU */
+static int rcu_nocb_gp_cleanup(struct rcu_state *rsp, struct rcu_node *rnp)
+{
+ return 0;
+}
+
+static void rcu_nocb_gp_set(struct rcu_node *rnp, int nrq)
+{
+}
+
+static void rcu_init_one_nocb(struct rcu_node *rnp)
+{
+}
static bool is_nocb_cpu(int cpu)
{
return 0;
}
-static bool nocb_cpu_expendable(int cpu)
-{
- return 1;
-}
-
static void __init rcu_boot_init_nocb_percpu_data(struct rcu_data *rdp)
{
}
{
}
-static void init_nocb_callback_list(struct rcu_data *rdp)
-{
-}
-
-static void __init rcu_init_nocb(void)
+static bool init_nocb_callback_list(struct rcu_data *rdp)
{
+ return false;
}
#endif /* #else #ifdef CONFIG_RCU_NOCB_CPU */
projects / mirror_ubuntu-jammy-kernel.git / blobdiff