cpumask_t coupled_cpus;
int requested_state[NR_CPUS];
atomic_t ready_waiting_counts;
+ atomic_t abort_barrier;
int online_count;
int refcnt;
int prevent;
static DEFINE_PER_CPU(struct call_single_data, cpuidle_coupled_poke_cb);
/*
- * The cpuidle_coupled_poked_mask mask is used to avoid calling
+ * The cpuidle_coupled_poke_pending mask is used to avoid calling
* __smp_call_function_single with the per cpu call_single_data struct already
* in use. This prevents a deadlock where two cpus are waiting for each others
* call_single_data struct to be available
*/
-static cpumask_t cpuidle_coupled_poked_mask;
+static cpumask_t cpuidle_coupled_poke_pending;
+
+/*
+ * The cpuidle_coupled_poked mask is used to ensure that each cpu has been poked
+ * once to minimize entering the ready loop with a poke pending, which would
+ * require aborting and retrying.
+ */
+static cpumask_t cpuidle_coupled_poked;
/**
* cpuidle_coupled_parallel_barrier - synchronize all online coupled cpus
return state;
}
-static void cpuidle_coupled_poked(void *info)
+static void cpuidle_coupled_handle_poke(void *info)
{
int cpu = (unsigned long)info;
- cpumask_clear_cpu(cpu, &cpuidle_coupled_poked_mask);
+ cpumask_set_cpu(cpu, &cpuidle_coupled_poked);
+ cpumask_clear_cpu(cpu, &cpuidle_coupled_poke_pending);
}
/**
{
struct call_single_data *csd = &per_cpu(cpuidle_coupled_poke_cb, cpu);
- if (!cpumask_test_and_set_cpu(cpu, &cpuidle_coupled_poked_mask))
+ if (!cpumask_test_and_set_cpu(cpu, &cpuidle_coupled_poke_pending))
__smp_call_function_single(cpu, csd, 0);
}
* @coupled: the struct coupled that contains the current cpu
* @next_state: the index in drv->states of the requested state for this cpu
*
- * Updates the requested idle state for the specified cpuidle device,
- * poking all coupled cpus out of idle if necessary to let them see the new
- * state.
+ * Updates the requested idle state for the specified cpuidle device.
+ * Returns the number of waiting cpus.
*/
-static void cpuidle_coupled_set_waiting(int cpu,
+static int cpuidle_coupled_set_waiting(int cpu,
struct cpuidle_coupled *coupled, int next_state)
{
- int w;
-
coupled->requested_state[cpu] = next_state;
/*
- * If this is the last cpu to enter the waiting state, poke
- * all the other cpus out of their waiting state so they can
- * enter a deeper state. This can race with one of the cpus
- * exiting the waiting state due to an interrupt and
- * decrementing waiting_count, see comment below.
- *
* The atomic_inc_return provides a write barrier to order the write
* to requested_state with the later write that increments ready_count.
*/
- w = atomic_inc_return(&coupled->ready_waiting_counts) & WAITING_MASK;
- if (w == coupled->online_count)
- cpuidle_coupled_poke_others(cpu, coupled);
+ return atomic_inc_return(&coupled->ready_waiting_counts) & WAITING_MASK;
}
/**
* been processed and the poke bit has been cleared.
*
* Other interrupts may also be processed while interrupts are enabled, so
- * need_resched() must be tested after turning interrupts off again to make sure
+ * need_resched() must be tested after this function returns to make sure
* the interrupt didn't schedule work that should take the cpu out of idle.
*
- * Returns 0 if need_resched was false, -EINTR if need_resched was true.
+ * Returns 0 if no poke was pending, 1 if a poke was cleared.
*/
static int cpuidle_coupled_clear_pokes(int cpu)
{
+ if (!cpumask_test_cpu(cpu, &cpuidle_coupled_poke_pending))
+ return 0;
+
local_irq_enable();
- while (cpumask_test_cpu(cpu, &cpuidle_coupled_poked_mask))
+ while (cpumask_test_cpu(cpu, &cpuidle_coupled_poke_pending))
cpu_relax();
local_irq_disable();
- return need_resched() ? -EINTR : 0;
+ return 1;
+}
+
+static bool cpuidle_coupled_any_pokes_pending(struct cpuidle_coupled *coupled)
+{
+ cpumask_t cpus;
+ int ret;
+
+ cpumask_and(&cpus, cpu_online_mask, &coupled->coupled_cpus);
+ ret = cpumask_and(&cpus, &cpuidle_coupled_poke_pending, &cpus);
+
+ return ret;
}
/**
{
int entered_state = -1;
struct cpuidle_coupled *coupled = dev->coupled;
+ int w;
if (!coupled)
return -EINVAL;
while (coupled->prevent) {
- if (cpuidle_coupled_clear_pokes(dev->cpu)) {
+ cpuidle_coupled_clear_pokes(dev->cpu);
+ if (need_resched()) {
local_irq_enable();
return entered_state;
}
/* Read barrier ensures online_count is read after prevent is cleared */
smp_rmb();
- cpuidle_coupled_set_waiting(dev->cpu, coupled, next_state);
+reset:
+ cpumask_clear_cpu(dev->cpu, &cpuidle_coupled_poked);
+
+ w = cpuidle_coupled_set_waiting(dev->cpu, coupled, next_state);
+ /*
+ * If this is the last cpu to enter the waiting state, poke
+ * all the other cpus out of their waiting state so they can
+ * enter a deeper state. This can race with one of the cpus
+ * exiting the waiting state due to an interrupt and
+ * decrementing waiting_count, see comment below.
+ */
+ if (w == coupled->online_count) {
+ cpumask_set_cpu(dev->cpu, &cpuidle_coupled_poked);
+ cpuidle_coupled_poke_others(dev->cpu, coupled);
+ }
retry:
/*
* Wait for all coupled cpus to be idle, using the deepest state
- * allowed for a single cpu.
+ * allowed for a single cpu. If this was not the poking cpu, wait
+ * for at least one poke before leaving to avoid a race where
+ * two cpus could arrive at the waiting loop at the same time,
+ * but the first of the two to arrive could skip the loop without
+ * processing the pokes from the last to arrive.
*/
- while (!cpuidle_coupled_cpus_waiting(coupled)) {
- if (cpuidle_coupled_clear_pokes(dev->cpu)) {
+ while (!cpuidle_coupled_cpus_waiting(coupled) ||
+ !cpumask_test_cpu(dev->cpu, &cpuidle_coupled_poked)) {
+ if (cpuidle_coupled_clear_pokes(dev->cpu))
+ continue;
+
+ if (need_resched()) {
cpuidle_coupled_set_not_waiting(dev->cpu, coupled);
goto out;
}
dev->safe_state_index);
}
- if (cpuidle_coupled_clear_pokes(dev->cpu)) {
+ cpuidle_coupled_clear_pokes(dev->cpu);
+ if (need_resched()) {
cpuidle_coupled_set_not_waiting(dev->cpu, coupled);
goto out;
}
+ /*
+ * Make sure final poke status for this cpu is visible before setting
+ * cpu as ready.
+ */
+ smp_wmb();
+
/*
* All coupled cpus are probably idle. There is a small chance that
* one of the other cpus just became active. Increment the ready count,
cpu_relax();
}
+ /*
+ * Make sure read of all cpus ready is done before reading pending pokes
+ */
+ smp_rmb();
+
+ /*
+ * There is a small chance that a cpu left and reentered idle after this
+ * cpu saw that all cpus were waiting. The cpu that reentered idle will
+ * have sent this cpu a poke, which will still be pending after the
+ * ready loop. The pending interrupt may be lost by the interrupt
+ * controller when entering the deep idle state. It's not possible to
+ * clear a pending interrupt without turning interrupts on and handling
+ * it, and it's too late to turn on interrupts here, so reset the
+ * coupled idle state of all cpus and retry.
+ */
+ if (cpuidle_coupled_any_pokes_pending(coupled)) {
+ cpuidle_coupled_set_done(dev->cpu, coupled);
+ /* Wait for all cpus to see the pending pokes */
+ cpuidle_coupled_parallel_barrier(dev, &coupled->abort_barrier);
+ goto reset;
+ }
+
/* all cpus have acked the coupled state */
next_state = cpuidle_coupled_get_state(dev, coupled);
coupled->refcnt++;
csd = &per_cpu(cpuidle_coupled_poke_cb, dev->cpu);
- csd->func = cpuidle_coupled_poked;
+ csd->func = cpuidle_coupled_handle_poke;
csd->info = (void *)(unsigned long)dev->cpu;
return 0;
projects / firefly-linux-kernel-4.4.55.git / blobdiff