static void invoke_rcu_core(void);
static void invoke_rcu_callbacks(struct rcu_state *rsp, struct rcu_data *rdp);
+/* rcuc/rcub kthread realtime priority */
+static int kthread_prio = CONFIG_RCU_KTHREAD_PRIO;
+module_param(kthread_prio, int, 0644);
+
/*
* Track the rcutorture test sequence number and the update version
* number within a given test. The rcutorture_testseq is incremented
/**
* rcu_nmi_enter - inform RCU of entry to NMI context
*
- * If the CPU was idle with dynamic ticks active, and there is no
- * irq handler running, this updates rdtp->dynticks_nmi to let the
- * RCU grace-period handling know that the CPU is active.
+ * If the CPU was idle from RCU's viewpoint, update rdtp->dynticks and
+ * rdtp->dynticks_nmi_nesting to let the RCU grace-period handling know
+ * that the CPU is active. This implementation permits nested NMIs, as
+ * long as the nesting level does not overflow an int. (You will probably
+ * run out of stack space first.)
*/
void rcu_nmi_enter(void)
{
struct rcu_dynticks *rdtp = this_cpu_ptr(&rcu_dynticks);
+ int incby = 2;
- if (rdtp->dynticks_nmi_nesting == 0 &&
- (atomic_read(&rdtp->dynticks) & 0x1))
- return;
- rdtp->dynticks_nmi_nesting++;
- smp_mb__before_atomic(); /* Force delay from prior write. */
- atomic_inc(&rdtp->dynticks);
- /* CPUs seeing atomic_inc() must see later RCU read-side crit sects */
- smp_mb__after_atomic(); /* See above. */
- WARN_ON_ONCE(!(atomic_read(&rdtp->dynticks) & 0x1));
+ /* Complain about underflow. */
+ WARN_ON_ONCE(rdtp->dynticks_nmi_nesting < 0);
+
+ /*
+ * If idle from RCU viewpoint, atomically increment ->dynticks
+ * to mark non-idle and increment ->dynticks_nmi_nesting by one.
+ * Otherwise, increment ->dynticks_nmi_nesting by two. This means
+ * if ->dynticks_nmi_nesting is equal to one, we are guaranteed
+ * to be in the outermost NMI handler that interrupted an RCU-idle
+ * period (observation due to Andy Lutomirski).
+ */
+ if (!(atomic_read(&rdtp->dynticks) & 0x1)) {
+ smp_mb__before_atomic(); /* Force delay from prior write. */
+ atomic_inc(&rdtp->dynticks);
+ /* atomic_inc() before later RCU read-side crit sects */
+ smp_mb__after_atomic(); /* See above. */
+ WARN_ON_ONCE(!(atomic_read(&rdtp->dynticks) & 0x1));
+ incby = 1;
+ }
+ rdtp->dynticks_nmi_nesting += incby;
+ barrier();
}
/**
* rcu_nmi_exit - inform RCU of exit from NMI context
*
- * If the CPU was idle with dynamic ticks active, and there is no
- * irq handler running, this updates rdtp->dynticks_nmi to let the
- * RCU grace-period handling know that the CPU is no longer active.
+ * If we are returning from the outermost NMI handler that interrupted an
+ * RCU-idle period, update rdtp->dynticks and rdtp->dynticks_nmi_nesting
+ * to let the RCU grace-period handling know that the CPU is back to
+ * being RCU-idle.
*/
void rcu_nmi_exit(void)
{
struct rcu_dynticks *rdtp = this_cpu_ptr(&rcu_dynticks);
- if (rdtp->dynticks_nmi_nesting == 0 ||
- --rdtp->dynticks_nmi_nesting != 0)
+ /*
+ * Check for ->dynticks_nmi_nesting underflow and bad ->dynticks.
+ * (We are exiting an NMI handler, so RCU better be paying attention
+ * to us!)
+ */
+ WARN_ON_ONCE(rdtp->dynticks_nmi_nesting <= 0);
+ WARN_ON_ONCE(!(atomic_read(&rdtp->dynticks) & 0x1));
+
+ /*
+ * If the nesting level is not 1, the CPU wasn't RCU-idle, so
+ * leave it in non-RCU-idle state.
+ */
+ if (rdtp->dynticks_nmi_nesting != 1) {
+ rdtp->dynticks_nmi_nesting -= 2;
return;
+ }
+
+ /* This NMI interrupted an RCU-idle CPU, restore RCU-idleness. */
+ rdtp->dynticks_nmi_nesting = 0;
/* CPUs seeing atomic_inc() must see prior RCU read-side crit sects */
smp_mb__before_atomic(); /* See above. */
atomic_inc(&rdtp->dynticks);
trace_rcu_fqs(rdp->rsp->name, rdp->gpnum, rdp->cpu, TPS("dti"));
return 1;
} else {
+ if (ULONG_CMP_LT(ACCESS_ONCE(rdp->gpnum) + ULONG_MAX / 4,
+ rdp->mynode->gpnum))
+ ACCESS_ONCE(rdp->gpwrap) = true;
return 0;
}
}
j1 = rcu_jiffies_till_stall_check();
ACCESS_ONCE(rsp->jiffies_stall) = j + j1;
rsp->jiffies_resched = j + j1 / 2;
+ rsp->n_force_qs_gpstart = ACCESS_ONCE(rsp->n_force_qs);
}
/*
}
}
-static void print_other_cpu_stall(struct rcu_state *rsp)
+static void print_other_cpu_stall(struct rcu_state *rsp, unsigned long gpnum)
{
int cpu;
long delta;
unsigned long flags;
+ unsigned long gpa;
+ unsigned long j;
int ndetected = 0;
struct rcu_node *rnp = rcu_get_root(rsp);
long totqlen = 0;
pr_cont("(detected by %d, t=%ld jiffies, g=%ld, c=%ld, q=%lu)\n",
smp_processor_id(), (long)(jiffies - rsp->gp_start),
(long)rsp->gpnum, (long)rsp->completed, totqlen);
- if (ndetected == 0)
- pr_err("INFO: Stall ended before state dump start\n");
- else
+ if (ndetected) {
rcu_dump_cpu_stacks(rsp);
+ } else {
+ if (ACCESS_ONCE(rsp->gpnum) != gpnum ||
+ ACCESS_ONCE(rsp->completed) == gpnum) {
+ pr_err("INFO: Stall ended before state dump start\n");
+ } else {
+ j = jiffies;
+ gpa = ACCESS_ONCE(rsp->gp_activity);
+ pr_err("All QSes seen, last %s kthread activity %ld (%ld-%ld), jiffies_till_next_fqs=%ld\n",
+ rsp->name, j - gpa, j, gpa,
+ jiffies_till_next_fqs);
+ /* In this case, the current CPU might be at fault. */
+ sched_show_task(current);
+ }
+ }
/* Complain about tasks blocking the grace period. */
ULONG_CMP_GE(j, js + RCU_STALL_RAT_DELAY)) {
/* They had a few time units to dump stack, so complain. */
- print_other_cpu_stall(rsp);
+ print_other_cpu_stall(rsp, gpnum);
}
}
bool ret;
/* Handle the ends of any preceding grace periods first. */
- if (rdp->completed == rnp->completed) {
+ if (rdp->completed == rnp->completed &&
+ !unlikely(ACCESS_ONCE(rdp->gpwrap))) {
/* No grace period end, so just accelerate recent callbacks. */
ret = rcu_accelerate_cbs(rsp, rnp, rdp);
trace_rcu_grace_period(rsp->name, rdp->gpnum, TPS("cpuend"));
}
- if (rdp->gpnum != rnp->gpnum) {
+ if (rdp->gpnum != rnp->gpnum || unlikely(ACCESS_ONCE(rdp->gpwrap))) {
/*
* If the current grace period is waiting for this CPU,
* set up to detect a quiescent state, otherwise don't
rdp->passed_quiesce = 0;
rdp->qs_pending = !!(rnp->qsmask & rdp->grpmask);
zero_cpu_stall_ticks(rdp);
+ ACCESS_ONCE(rdp->gpwrap) = false;
}
return ret;
}
local_irq_save(flags);
rnp = rdp->mynode;
if ((rdp->gpnum == ACCESS_ONCE(rnp->gpnum) &&
- rdp->completed == ACCESS_ONCE(rnp->completed)) || /* w/out lock. */
+ rdp->completed == ACCESS_ONCE(rnp->completed) &&
+ !unlikely(ACCESS_ONCE(rdp->gpwrap))) || /* w/out lock. */
!raw_spin_trylock(&rnp->lock)) { /* irqs already off, so later. */
local_irq_restore(flags);
return;
struct rcu_data *rdp;
struct rcu_node *rnp = rcu_get_root(rsp);
+ ACCESS_ONCE(rsp->gp_activity) = jiffies;
rcu_bind_gp_kthread();
raw_spin_lock_irq(&rnp->lock);
smp_mb__after_unlock_lock();
rnp->grphi, rnp->qsmask);
raw_spin_unlock_irq(&rnp->lock);
cond_resched_rcu_qs();
+ ACCESS_ONCE(rsp->gp_activity) = jiffies;
}
mutex_unlock(&rsp->onoff_mutex);
unsigned long maxj;
struct rcu_node *rnp = rcu_get_root(rsp);
+ ACCESS_ONCE(rsp->gp_activity) = jiffies;
rsp->n_force_qs++;
if (fqs_state == RCU_SAVE_DYNTICK) {
/* Collect dyntick-idle snapshots. */
struct rcu_data *rdp;
struct rcu_node *rnp = rcu_get_root(rsp);
+ ACCESS_ONCE(rsp->gp_activity) = jiffies;
raw_spin_lock_irq(&rnp->lock);
smp_mb__after_unlock_lock();
gp_duration = jiffies - rsp->gp_start;
nocb += rcu_future_gp_cleanup(rsp, rnp);
raw_spin_unlock_irq(&rnp->lock);
cond_resched_rcu_qs();
+ ACCESS_ONCE(rsp->gp_activity) = jiffies;
}
rnp = rcu_get_root(rsp);
raw_spin_lock_irq(&rnp->lock);
if (rcu_gp_init(rsp))
break;
cond_resched_rcu_qs();
+ ACCESS_ONCE(rsp->gp_activity) = jiffies;
WARN_ON(signal_pending(current));
trace_rcu_grace_period(rsp->name,
ACCESS_ONCE(rsp->gpnum),
ACCESS_ONCE(rsp->gpnum),
TPS("fqsend"));
cond_resched_rcu_qs();
+ ACCESS_ONCE(rsp->gp_activity) = jiffies;
} else {
/* Deal with stray signal. */
cond_resched_rcu_qs();
+ ACCESS_ONCE(rsp->gp_activity) = jiffies;
WARN_ON(signal_pending(current));
trace_rcu_grace_period(rsp->name,
ACCESS_ONCE(rsp->gpnum),
raw_spin_lock_irqsave(&rnp->lock, flags);
smp_mb__after_unlock_lock();
if (rdp->passed_quiesce == 0 || rdp->gpnum != rnp->gpnum ||
- rnp->completed == rnp->gpnum) {
+ rnp->completed == rnp->gpnum || rdp->gpwrap) {
/*
* The grace period in which this quiescent state was
}
/* Has a new RCU grace period started? */
- if (ACCESS_ONCE(rnp->gpnum) != rdp->gpnum) { /* outside lock */
+ if (ACCESS_ONCE(rnp->gpnum) != rdp->gpnum ||
+ unlikely(ACCESS_ONCE(rdp->gpwrap))) { /* outside lock */
rdp->n_rp_gp_started++;
return 1;
}
static int __init rcu_spawn_gp_kthread(void)
{
unsigned long flags;
+ int kthread_prio_in = kthread_prio;
struct rcu_node *rnp;
struct rcu_state *rsp;
+ struct sched_param sp;
struct task_struct *t;
+ /* Force priority into range. */
+ if (IS_ENABLED(CONFIG_RCU_BOOST) && kthread_prio < 1)
+ kthread_prio = 1;
+ else if (kthread_prio < 0)
+ kthread_prio = 0;
+ else if (kthread_prio > 99)
+ kthread_prio = 99;
+ if (kthread_prio != kthread_prio_in)
+ pr_alert("rcu_spawn_gp_kthread(): Limited prio to %d from %d\n",
+ kthread_prio, kthread_prio_in);
+
rcu_scheduler_fully_active = 1;
for_each_rcu_flavor(rsp) {
- t = kthread_run(rcu_gp_kthread, rsp, "%s", rsp->name);
+ t = kthread_create(rcu_gp_kthread, rsp, "%s", rsp->name);
BUG_ON(IS_ERR(t));
rnp = rcu_get_root(rsp);
raw_spin_lock_irqsave(&rnp->lock, flags);
rsp->gp_kthread = t;
+ if (kthread_prio) {
+ sp.sched_priority = kthread_prio;
+ sched_setscheduler_nocheck(t, SCHED_FIFO, &sp);
+ }
+ wake_up_process(t);
raw_spin_unlock_irqrestore(&rnp->lock, flags);
}
rcu_spawn_nocb_kthreads();
git.openpandora.org / pandora-kernel.git / blobdiff