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authorPaul E. McKenney <paulmck@linux.vnet.ibm.com>2015-08-04 08:40:58 -0700
committerPaul E. McKenney <paulmck@linux.vnet.ibm.com>2015-08-04 08:40:58 -0700
commit8ff4fbfd69a6c7b9598f8c1f2df34f89bac02c1a (patch)
treea56504a1f6223a9a755e30ab4ce0fbeb79b94f8d /kernel/rcu/tree.c
parent9a54f98e341d09793247a6e598012edefb5ae7cb (diff)
parentaf859beaaba4d57883b08f4acbcb3974bc1f975e (diff)
downloadlinux-sh-8ff4fbfd69a6c7b9598f8c1f2df34f89bac02c1a.tar.gz
Merge branches 'fixes.2015.07.22a' and 'initexp.2015.08.04a' into HEAD
fixes.2015.07.22a: Miscellaneous fixes. initexp.2015.08.04a: Initialization and expedited updates. (Single branch due to conflicts.)
Diffstat (limited to 'kernel/rcu/tree.c')
-rw-r--r--kernel/rcu/tree.c589
1 files changed, 327 insertions, 262 deletions
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 0a73d26357a2..9f75f25cc5d9 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -70,6 +70,8 @@ MODULE_ALIAS("rcutree");
static struct lock_class_key rcu_node_class[RCU_NUM_LVLS];
static struct lock_class_key rcu_fqs_class[RCU_NUM_LVLS];
+static struct lock_class_key rcu_exp_class[RCU_NUM_LVLS];
+static struct lock_class_key rcu_exp_sched_class[RCU_NUM_LVLS];
/*
* In order to export the rcu_state name to the tracing tools, it
@@ -124,13 +126,8 @@ module_param(rcu_fanout_exact, bool, 0444);
static int rcu_fanout_leaf = RCU_FANOUT_LEAF;
module_param(rcu_fanout_leaf, int, 0444);
int rcu_num_lvls __read_mostly = RCU_NUM_LVLS;
-static int num_rcu_lvl[] = { /* Number of rcu_nodes at specified level. */
- NUM_RCU_LVL_0,
- NUM_RCU_LVL_1,
- NUM_RCU_LVL_2,
- NUM_RCU_LVL_3,
- NUM_RCU_LVL_4,
-};
+/* Number of rcu_nodes at specified level. */
+static int num_rcu_lvl[] = NUM_RCU_LVL_INIT;
int rcu_num_nodes __read_mostly = NUM_RCU_NODES; /* Total # rcu_nodes in use. */
/*
@@ -1178,9 +1175,11 @@ static void rcu_check_gp_kthread_starvation(struct rcu_state *rsp)
j = jiffies;
gpa = READ_ONCE(rsp->gp_activity);
if (j - gpa > 2 * HZ)
- pr_err("%s kthread starved for %ld jiffies! g%lu c%lu f%#x\n",
+ pr_err("%s kthread starved for %ld jiffies! g%lu c%lu f%#x s%d ->state=%#lx\n",
rsp->name, j - gpa,
- rsp->gpnum, rsp->completed, rsp->gp_flags);
+ rsp->gpnum, rsp->completed,
+ rsp->gp_flags, rsp->gp_state,
+ rsp->gp_kthread ? rsp->gp_kthread->state : 0);
}
/*
@@ -1906,6 +1905,26 @@ static int rcu_gp_init(struct rcu_state *rsp)
}
/*
+ * Helper function for wait_event_interruptible_timeout() wakeup
+ * at force-quiescent-state time.
+ */
+static bool rcu_gp_fqs_check_wake(struct rcu_state *rsp, int *gfp)
+{
+ struct rcu_node *rnp = rcu_get_root(rsp);
+
+ /* Someone like call_rcu() requested a force-quiescent-state scan. */
+ *gfp = READ_ONCE(rsp->gp_flags);
+ if (*gfp & RCU_GP_FLAG_FQS)
+ return true;
+
+ /* The current grace period has completed. */
+ if (!READ_ONCE(rnp->qsmask) && !rcu_preempt_blocked_readers_cgp(rnp))
+ return true;
+
+ return false;
+}
+
+/*
* Do one round of quiescent-state forcing.
*/
static int rcu_gp_fqs(struct rcu_state *rsp, int fqs_state_in)
@@ -2041,6 +2060,7 @@ static int __noreturn rcu_gp_kthread(void *arg)
wait_event_interruptible(rsp->gp_wq,
READ_ONCE(rsp->gp_flags) &
RCU_GP_FLAG_INIT);
+ rsp->gp_state = RCU_GP_DONE_GPS;
/* Locking provides needed memory barrier. */
if (rcu_gp_init(rsp))
break;
@@ -2068,11 +2088,8 @@ static int __noreturn rcu_gp_kthread(void *arg)
TPS("fqswait"));
rsp->gp_state = RCU_GP_WAIT_FQS;
ret = wait_event_interruptible_timeout(rsp->gp_wq,
- ((gf = READ_ONCE(rsp->gp_flags)) &
- RCU_GP_FLAG_FQS) ||
- (!READ_ONCE(rnp->qsmask) &&
- !rcu_preempt_blocked_readers_cgp(rnp)),
- j);
+ rcu_gp_fqs_check_wake(rsp, &gf), j);
+ rsp->gp_state = RCU_GP_DOING_FQS;
/* Locking provides needed memory barriers. */
/* If grace period done, leave loop. */
if (!READ_ONCE(rnp->qsmask) &&
@@ -2110,7 +2127,9 @@ static int __noreturn rcu_gp_kthread(void *arg)
}
/* Handle grace-period end. */
+ rsp->gp_state = RCU_GP_CLEANUP;
rcu_gp_cleanup(rsp);
+ rsp->gp_state = RCU_GP_CLEANED;
}
}
@@ -3305,23 +3324,195 @@ void cond_synchronize_sched(unsigned long oldstate)
}
EXPORT_SYMBOL_GPL(cond_synchronize_sched);
-static int synchronize_sched_expedited_cpu_stop(void *data)
+/* Adjust sequence number for start of update-side operation. */
+static void rcu_seq_start(unsigned long *sp)
+{
+ WRITE_ONCE(*sp, *sp + 1);
+ smp_mb(); /* Ensure update-side operation after counter increment. */
+ WARN_ON_ONCE(!(*sp & 0x1));
+}
+
+/* Adjust sequence number for end of update-side operation. */
+static void rcu_seq_end(unsigned long *sp)
+{
+ smp_mb(); /* Ensure update-side operation before counter increment. */
+ WRITE_ONCE(*sp, *sp + 1);
+ WARN_ON_ONCE(*sp & 0x1);
+}
+
+/* Take a snapshot of the update side's sequence number. */
+static unsigned long rcu_seq_snap(unsigned long *sp)
+{
+ unsigned long s;
+
+ smp_mb(); /* Caller's modifications seen first by other CPUs. */
+ s = (READ_ONCE(*sp) + 3) & ~0x1;
+ smp_mb(); /* Above access must not bleed into critical section. */
+ return s;
+}
+
+/*
+ * Given a snapshot from rcu_seq_snap(), determine whether or not a
+ * full update-side operation has occurred.
+ */
+static bool rcu_seq_done(unsigned long *sp, unsigned long s)
+{
+ return ULONG_CMP_GE(READ_ONCE(*sp), s);
+}
+
+/* Wrapper functions for expedited grace periods. */
+static void rcu_exp_gp_seq_start(struct rcu_state *rsp)
+{
+ rcu_seq_start(&rsp->expedited_sequence);
+}
+static void rcu_exp_gp_seq_end(struct rcu_state *rsp)
+{
+ rcu_seq_end(&rsp->expedited_sequence);
+ smp_mb(); /* Ensure that consecutive grace periods serialize. */
+}
+static unsigned long rcu_exp_gp_seq_snap(struct rcu_state *rsp)
+{
+ return rcu_seq_snap(&rsp->expedited_sequence);
+}
+static bool rcu_exp_gp_seq_done(struct rcu_state *rsp, unsigned long s)
+{
+ return rcu_seq_done(&rsp->expedited_sequence, s);
+}
+
+/* Common code for synchronize_{rcu,sched}_expedited() work-done checking. */
+static bool sync_exp_work_done(struct rcu_state *rsp, struct rcu_node *rnp,
+ struct rcu_data *rdp,
+ atomic_long_t *stat, unsigned long s)
{
+ if (rcu_exp_gp_seq_done(rsp, s)) {
+ if (rnp)
+ mutex_unlock(&rnp->exp_funnel_mutex);
+ else if (rdp)
+ mutex_unlock(&rdp->exp_funnel_mutex);
+ /* Ensure test happens before caller kfree(). */
+ smp_mb__before_atomic(); /* ^^^ */
+ atomic_long_inc(stat);
+ return true;
+ }
+ return false;
+}
+
+/*
+ * Funnel-lock acquisition for expedited grace periods. Returns a
+ * pointer to the root rcu_node structure, or NULL if some other
+ * task did the expedited grace period for us.
+ */
+static struct rcu_node *exp_funnel_lock(struct rcu_state *rsp, unsigned long s)
+{
+ struct rcu_data *rdp;
+ struct rcu_node *rnp0;
+ struct rcu_node *rnp1 = NULL;
+
/*
- * There must be a full memory barrier on each affected CPU
- * between the time that try_stop_cpus() is called and the
- * time that it returns.
- *
- * In the current initial implementation of cpu_stop, the
- * above condition is already met when the control reaches
- * this point and the following smp_mb() is not strictly
- * necessary. Do smp_mb() anyway for documentation and
- * robustness against future implementation changes.
+ * First try directly acquiring the root lock in order to reduce
+ * latency in the common case where expedited grace periods are
+ * rare. We check mutex_is_locked() to avoid pathological levels of
+ * memory contention on ->exp_funnel_mutex in the heavy-load case.
*/
- smp_mb(); /* See above comment block. */
+ rnp0 = rcu_get_root(rsp);
+ if (!mutex_is_locked(&rnp0->exp_funnel_mutex)) {
+ if (mutex_trylock(&rnp0->exp_funnel_mutex)) {
+ if (sync_exp_work_done(rsp, rnp0, NULL,
+ &rsp->expedited_workdone0, s))
+ return NULL;
+ return rnp0;
+ }
+ }
+
+ /*
+ * Each pass through the following loop works its way
+ * up the rcu_node tree, returning if others have done the
+ * work or otherwise falls through holding the root rnp's
+ * ->exp_funnel_mutex. The mapping from CPU to rcu_node structure
+ * can be inexact, as it is just promoting locality and is not
+ * strictly needed for correctness.
+ */
+ rdp = per_cpu_ptr(rsp->rda, raw_smp_processor_id());
+ if (sync_exp_work_done(rsp, NULL, NULL, &rsp->expedited_workdone1, s))
+ return NULL;
+ mutex_lock(&rdp->exp_funnel_mutex);
+ rnp0 = rdp->mynode;
+ for (; rnp0 != NULL; rnp0 = rnp0->parent) {
+ if (sync_exp_work_done(rsp, rnp1, rdp,
+ &rsp->expedited_workdone2, s))
+ return NULL;
+ mutex_lock(&rnp0->exp_funnel_mutex);
+ if (rnp1)
+ mutex_unlock(&rnp1->exp_funnel_mutex);
+ else
+ mutex_unlock(&rdp->exp_funnel_mutex);
+ rnp1 = rnp0;
+ }
+ if (sync_exp_work_done(rsp, rnp1, rdp,
+ &rsp->expedited_workdone3, s))
+ return NULL;
+ return rnp1;
+}
+
+/* Invoked on each online non-idle CPU for expedited quiescent state. */
+static int synchronize_sched_expedited_cpu_stop(void *data)
+{
+ struct rcu_data *rdp = data;
+ struct rcu_state *rsp = rdp->rsp;
+
+ /* We are here: If we are last, do the wakeup. */
+ rdp->exp_done = true;
+ if (atomic_dec_and_test(&rsp->expedited_need_qs))
+ wake_up(&rsp->expedited_wq);
return 0;
}
+static void synchronize_sched_expedited_wait(struct rcu_state *rsp)
+{
+ int cpu;
+ unsigned long jiffies_stall;
+ unsigned long jiffies_start;
+ struct rcu_data *rdp;
+ int ret;
+
+ jiffies_stall = rcu_jiffies_till_stall_check();
+ jiffies_start = jiffies;
+
+ for (;;) {
+ ret = wait_event_interruptible_timeout(
+ rsp->expedited_wq,
+ !atomic_read(&rsp->expedited_need_qs),
+ jiffies_stall);
+ if (ret > 0)
+ return;
+ if (ret < 0) {
+ /* Hit a signal, disable CPU stall warnings. */
+ wait_event(rsp->expedited_wq,
+ !atomic_read(&rsp->expedited_need_qs));
+ return;
+ }
+ pr_err("INFO: %s detected expedited stalls on CPUs: {",
+ rsp->name);
+ for_each_online_cpu(cpu) {
+ rdp = per_cpu_ptr(rsp->rda, cpu);
+
+ if (rdp->exp_done)
+ continue;
+ pr_cont(" %d", cpu);
+ }
+ pr_cont(" } %lu jiffies s: %lu\n",
+ jiffies - jiffies_start, rsp->expedited_sequence);
+ for_each_online_cpu(cpu) {
+ rdp = per_cpu_ptr(rsp->rda, cpu);
+
+ if (rdp->exp_done)
+ continue;
+ dump_cpu_task(cpu);
+ }
+ jiffies_stall = 3 * rcu_jiffies_till_stall_check() + 3;
+ }
+}
+
/**
* synchronize_sched_expedited - Brute-force RCU-sched grace period
*
@@ -3333,58 +3524,21 @@ static int synchronize_sched_expedited_cpu_stop(void *data)
* restructure your code to batch your updates, and then use a single
* synchronize_sched() instead.
*
- * This implementation can be thought of as an application of ticket
- * locking to RCU, with sync_sched_expedited_started and
- * sync_sched_expedited_done taking on the roles of the halves
- * of the ticket-lock word. Each task atomically increments
- * sync_sched_expedited_started upon entry, snapshotting the old value,
- * then attempts to stop all the CPUs. If this succeeds, then each
- * CPU will have executed a context switch, resulting in an RCU-sched
- * grace period. We are then done, so we use atomic_cmpxchg() to
- * update sync_sched_expedited_done to match our snapshot -- but
- * only if someone else has not already advanced past our snapshot.
- *
- * On the other hand, if try_stop_cpus() fails, we check the value
- * of sync_sched_expedited_done. If it has advanced past our
- * initial snapshot, then someone else must have forced a grace period
- * some time after we took our snapshot. In this case, our work is
- * done for us, and we can simply return. Otherwise, we try again,
- * but keep our initial snapshot for purposes of checking for someone
- * doing our work for us.
- *
- * If we fail too many times in a row, we fall back to synchronize_sched().
+ * This implementation can be thought of as an application of sequence
+ * locking to expedited grace periods, but using the sequence counter to
+ * determine when someone else has already done the work instead of for
+ * retrying readers.
*/
void synchronize_sched_expedited(void)
{
- cpumask_var_t cm;
- bool cma = false;
int cpu;
- long firstsnap, s, snap;
- int trycount = 0;
+ unsigned long s;
+ struct rcu_node *rnp;
struct rcu_state *rsp = &rcu_sched_state;
- /*
- * If we are in danger of counter wrap, just do synchronize_sched().
- * By allowing sync_sched_expedited_started to advance no more than
- * ULONG_MAX/8 ahead of sync_sched_expedited_done, we are ensuring
- * that more than 3.5 billion CPUs would be required to force a
- * counter wrap on a 32-bit system. Quite a few more CPUs would of
- * course be required on a 64-bit system.
- */
- if (ULONG_CMP_GE((ulong)atomic_long_read(&rsp->expedited_start),
- (ulong)atomic_long_read(&rsp->expedited_done) +
- ULONG_MAX / 8)) {
- wait_rcu_gp(call_rcu_sched);
- atomic_long_inc(&rsp->expedited_wrap);
- return;
- }
+ /* Take a snapshot of the sequence number. */
+ s = rcu_exp_gp_seq_snap(rsp);
- /*
- * Take a ticket. Note that atomic_inc_return() implies a
- * full memory barrier.
- */
- snap = atomic_long_inc_return(&rsp->expedited_start);
- firstsnap = snap;
if (!try_get_online_cpus()) {
/* CPU hotplug operation in flight, fall back to normal GP. */
wait_rcu_gp(call_rcu_sched);
@@ -3393,100 +3547,38 @@ void synchronize_sched_expedited(void)
}
WARN_ON_ONCE(cpu_is_offline(raw_smp_processor_id()));
- /* Offline CPUs, idle CPUs, and any CPU we run on are quiescent. */
- cma = zalloc_cpumask_var(&cm, GFP_KERNEL);
- if (cma) {
- cpumask_copy(cm, cpu_online_mask);
- cpumask_clear_cpu(raw_smp_processor_id(), cm);
- for_each_cpu(cpu, cm) {
- struct rcu_dynticks *rdtp = &per_cpu(rcu_dynticks, cpu);
-
- if (!(atomic_add_return(0, &rdtp->dynticks) & 0x1))
- cpumask_clear_cpu(cpu, cm);
- }
- if (cpumask_weight(cm) == 0)
- goto all_cpus_idle;
+ rnp = exp_funnel_lock(rsp, s);
+ if (rnp == NULL) {
+ put_online_cpus();
+ return; /* Someone else did our work for us. */
}
- /*
- * Each pass through the following loop attempts to force a
- * context switch on each CPU.
- */
- while (try_stop_cpus(cma ? cm : cpu_online_mask,
- synchronize_sched_expedited_cpu_stop,
- NULL) == -EAGAIN) {
- put_online_cpus();
- atomic_long_inc(&rsp->expedited_tryfail);
-
- /* Check to see if someone else did our work for us. */
- s = atomic_long_read(&rsp->expedited_done);
- if (ULONG_CMP_GE((ulong)s, (ulong)firstsnap)) {
- /* ensure test happens before caller kfree */
- smp_mb__before_atomic(); /* ^^^ */
- atomic_long_inc(&rsp->expedited_workdone1);
- free_cpumask_var(cm);
- return;
- }
+ rcu_exp_gp_seq_start(rsp);
- /* No joy, try again later. Or just synchronize_sched(). */
- if (trycount++ < 10) {
- udelay(trycount * num_online_cpus());
- } else {
- wait_rcu_gp(call_rcu_sched);
- atomic_long_inc(&rsp->expedited_normal);
- free_cpumask_var(cm);
- return;
- }
+ /* Stop each CPU that is online, non-idle, and not us. */
+ init_waitqueue_head(&rsp->expedited_wq);
+ atomic_set(&rsp->expedited_need_qs, 1); /* Extra count avoids race. */
+ for_each_online_cpu(cpu) {
+ struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu);
+ struct rcu_dynticks *rdtp = &per_cpu(rcu_dynticks, cpu);
- /* Recheck to see if someone else did our work for us. */
- s = atomic_long_read(&rsp->expedited_done);
- if (ULONG_CMP_GE((ulong)s, (ulong)firstsnap)) {
- /* ensure test happens before caller kfree */
- smp_mb__before_atomic(); /* ^^^ */
- atomic_long_inc(&rsp->expedited_workdone2);
- free_cpumask_var(cm);
- return;
- }
+ rdp->exp_done = false;
- /*
- * Refetching sync_sched_expedited_started allows later
- * callers to piggyback on our grace period. We retry
- * after they started, so our grace period works for them,
- * and they started after our first try, so their grace
- * period works for us.
- */
- if (!try_get_online_cpus()) {
- /* CPU hotplug operation in flight, use normal GP. */
- wait_rcu_gp(call_rcu_sched);
- atomic_long_inc(&rsp->expedited_normal);
- free_cpumask_var(cm);
- return;
- }
- snap = atomic_long_read(&rsp->expedited_start);
- smp_mb(); /* ensure read is before try_stop_cpus(). */
+ /* Skip our CPU and any idle CPUs. */
+ if (raw_smp_processor_id() == cpu ||
+ !(atomic_add_return(0, &rdtp->dynticks) & 0x1))
+ continue;
+ atomic_inc(&rsp->expedited_need_qs);
+ stop_one_cpu_nowait(cpu, synchronize_sched_expedited_cpu_stop,
+ rdp, &rdp->exp_stop_work);
}
- atomic_long_inc(&rsp->expedited_stoppedcpus);
-all_cpus_idle:
- free_cpumask_var(cm);
+ /* Remove extra count and, if necessary, wait for CPUs to stop. */
+ if (!atomic_dec_and_test(&rsp->expedited_need_qs))
+ synchronize_sched_expedited_wait(rsp);
- /*
- * Everyone up to our most recent fetch is covered by our grace
- * period. Update the counter, but only if our work is still
- * relevant -- which it won't be if someone who started later
- * than we did already did their update.
- */
- do {
- atomic_long_inc(&rsp->expedited_done_tries);
- s = atomic_long_read(&rsp->expedited_done);
- if (ULONG_CMP_GE((ulong)s, (ulong)snap)) {
- /* ensure test happens before caller kfree */
- smp_mb__before_atomic(); /* ^^^ */
- atomic_long_inc(&rsp->expedited_done_lost);
- break;
- }
- } while (atomic_long_cmpxchg(&rsp->expedited_done, s, snap) != s);
- atomic_long_inc(&rsp->expedited_done_exit);
+ rcu_exp_gp_seq_end(rsp);
+ mutex_unlock(&rnp->exp_funnel_mutex);
put_online_cpus();
}
@@ -3623,10 +3715,10 @@ static void rcu_barrier_callback(struct rcu_head *rhp)
struct rcu_state *rsp = rdp->rsp;
if (atomic_dec_and_test(&rsp->barrier_cpu_count)) {
- _rcu_barrier_trace(rsp, "LastCB", -1, rsp->n_barrier_done);
+ _rcu_barrier_trace(rsp, "LastCB", -1, rsp->barrier_sequence);
complete(&rsp->barrier_completion);
} else {
- _rcu_barrier_trace(rsp, "CB", -1, rsp->n_barrier_done);
+ _rcu_barrier_trace(rsp, "CB", -1, rsp->barrier_sequence);
}
}
@@ -3638,7 +3730,7 @@ static void rcu_barrier_func(void *type)
struct rcu_state *rsp = type;
struct rcu_data *rdp = raw_cpu_ptr(rsp->rda);
- _rcu_barrier_trace(rsp, "IRQ", -1, rsp->n_barrier_done);
+ _rcu_barrier_trace(rsp, "IRQ", -1, rsp->barrier_sequence);
atomic_inc(&rsp->barrier_cpu_count);
rsp->call(&rdp->barrier_head, rcu_barrier_callback);
}
@@ -3651,55 +3743,24 @@ static void _rcu_barrier(struct rcu_state *rsp)
{
int cpu;
struct rcu_data *rdp;
- unsigned long snap = READ_ONCE(rsp->n_barrier_done);
- unsigned long snap_done;
+ unsigned long s = rcu_seq_snap(&rsp->barrier_sequence);
- _rcu_barrier_trace(rsp, "Begin", -1, snap);
+ _rcu_barrier_trace(rsp, "Begin", -1, s);
/* Take mutex to serialize concurrent rcu_barrier() requests. */
mutex_lock(&rsp->barrier_mutex);
- /*
- * Ensure that all prior references, including to ->n_barrier_done,
- * are ordered before the _rcu_barrier() machinery.
- */
- smp_mb(); /* See above block comment. */
-
- /*
- * Recheck ->n_barrier_done to see if others did our work for us.
- * This means checking ->n_barrier_done for an even-to-odd-to-even
- * transition. The "if" expression below therefore rounds the old
- * value up to the next even number and adds two before comparing.
- */
- snap_done = rsp->n_barrier_done;
- _rcu_barrier_trace(rsp, "Check", -1, snap_done);
-
- /*
- * If the value in snap is odd, we needed to wait for the current
- * rcu_barrier() to complete, then wait for the next one, in other
- * words, we need the value of snap_done to be three larger than
- * the value of snap. On the other hand, if the value in snap is
- * even, we only had to wait for the next rcu_barrier() to complete,
- * in other words, we need the value of snap_done to be only two
- * greater than the value of snap. The "(snap + 3) & ~0x1" computes
- * this for us (thank you, Linus!).
- */
- if (ULONG_CMP_GE(snap_done, (snap + 3) & ~0x1)) {
- _rcu_barrier_trace(rsp, "EarlyExit", -1, snap_done);
+ /* Did someone else do our work for us? */
+ if (rcu_seq_done(&rsp->barrier_sequence, s)) {
+ _rcu_barrier_trace(rsp, "EarlyExit", -1, rsp->barrier_sequence);
smp_mb(); /* caller's subsequent code after above check. */
mutex_unlock(&rsp->barrier_mutex);
return;
}
- /*
- * Increment ->n_barrier_done to avoid duplicate work. Use
- * WRITE_ONCE() to prevent the compiler from speculating
- * the increment to precede the early-exit check.
- */
- WRITE_ONCE(rsp->n_barrier_done, rsp->n_barrier_done + 1);
- WARN_ON_ONCE((rsp->n_barrier_done & 0x1) != 1);
- _rcu_barrier_trace(rsp, "Inc1", -1, rsp->n_barrier_done);
- smp_mb(); /* Order ->n_barrier_done increment with below mechanism. */
+ /* Mark the start of the barrier operation. */
+ rcu_seq_start(&rsp->barrier_sequence);
+ _rcu_barrier_trace(rsp, "Inc1", -1, rsp->barrier_sequence);
/*
* Initialize the count to one rather than to zero in order to
@@ -3723,10 +3784,10 @@ static void _rcu_barrier(struct rcu_state *rsp)
if (rcu_is_nocb_cpu(cpu)) {
if (!rcu_nocb_cpu_needs_barrier(rsp, cpu)) {
_rcu_barrier_trace(rsp, "OfflineNoCB", cpu,
- rsp->n_barrier_done);
+ rsp->barrier_sequence);
} else {
_rcu_barrier_trace(rsp, "OnlineNoCB", cpu,
- rsp->n_barrier_done);
+ rsp->barrier_sequence);
smp_mb__before_atomic();
atomic_inc(&rsp->barrier_cpu_count);
__call_rcu(&rdp->barrier_head,
@@ -3734,11 +3795,11 @@ static void _rcu_barrier(struct rcu_state *rsp)
}
} else if (READ_ONCE(rdp->qlen)) {
_rcu_barrier_trace(rsp, "OnlineQ", cpu,
- rsp->n_barrier_done);
+ rsp->barrier_sequence);
smp_call_function_single(cpu, rcu_barrier_func, rsp, 1);
} else {
_rcu_barrier_trace(rsp, "OnlineNQ", cpu,
- rsp->n_barrier_done);
+ rsp->barrier_sequence);
}
}
put_online_cpus();
@@ -3750,16 +3811,13 @@ static void _rcu_barrier(struct rcu_state *rsp)
if (atomic_dec_and_test(&rsp->barrier_cpu_count))
complete(&rsp->barrier_completion);
- /* Increment ->n_barrier_done to prevent duplicate work. */
- smp_mb(); /* Keep increment after above mechanism. */
- WRITE_ONCE(rsp->n_barrier_done, rsp->n_barrier_done + 1);
- WARN_ON_ONCE((rsp->n_barrier_done & 0x1) != 0);
- _rcu_barrier_trace(rsp, "Inc2", -1, rsp->n_barrier_done);
- smp_mb(); /* Keep increment before caller's subsequent code. */
-
/* Wait for all rcu_barrier_callback() callbacks to be invoked. */
wait_for_completion(&rsp->barrier_completion);
+ /* Mark the end of the barrier operation. */
+ _rcu_barrier_trace(rsp, "Inc2", -1, rsp->barrier_sequence);
+ rcu_seq_end(&rsp->barrier_sequence);
+
/* Other rcu_barrier() invocations can now safely proceed. */
mutex_unlock(&rsp->barrier_mutex);
}
@@ -3822,6 +3880,7 @@ rcu_boot_init_percpu_data(int cpu, struct rcu_state *rsp)
WARN_ON_ONCE(atomic_read(&rdp->dynticks->dynticks) != 1);
rdp->cpu = cpu;
rdp->rsp = rsp;
+ mutex_init(&rdp->exp_funnel_mutex);
rcu_boot_init_nocb_percpu_data(rdp);
raw_spin_unlock_irqrestore(&rnp->lock, flags);
}
@@ -4013,22 +4072,22 @@ void rcu_scheduler_starting(void)
* Compute the per-level fanout, either using the exact fanout specified
* or balancing the tree, depending on the rcu_fanout_exact boot parameter.
*/
-static void __init rcu_init_levelspread(struct rcu_state *rsp)
+static void __init rcu_init_levelspread(int *levelspread, const int *levelcnt)
{
int i;
if (rcu_fanout_exact) {
- rsp->levelspread[rcu_num_lvls - 1] = rcu_fanout_leaf;
+ levelspread[rcu_num_lvls - 1] = rcu_fanout_leaf;
for (i = rcu_num_lvls - 2; i >= 0; i--)
- rsp->levelspread[i] = RCU_FANOUT;
+ levelspread[i] = RCU_FANOUT;
} else {
int ccur;
int cprv;
cprv = nr_cpu_ids;
for (i = rcu_num_lvls - 1; i >= 0; i--) {
- ccur = rsp->levelcnt[i];
- rsp->levelspread[i] = (cprv + ccur - 1) / ccur;
+ ccur = levelcnt[i];
+ levelspread[i] = (cprv + ccur - 1) / ccur;
cprv = ccur;
}
}
@@ -4040,23 +4099,20 @@ static void __init rcu_init_levelspread(struct rcu_state *rsp)
static void __init rcu_init_one(struct rcu_state *rsp,
struct rcu_data __percpu *rda)
{
- static const char * const buf[] = {
- "rcu_node_0",
- "rcu_node_1",
- "rcu_node_2",
- "rcu_node_3" }; /* Match MAX_RCU_LVLS */
- static const char * const fqs[] = {
- "rcu_node_fqs_0",
- "rcu_node_fqs_1",
- "rcu_node_fqs_2",
- "rcu_node_fqs_3" }; /* Match MAX_RCU_LVLS */
+ static const char * const buf[] = RCU_NODE_NAME_INIT;
+ static const char * const fqs[] = RCU_FQS_NAME_INIT;
+ static const char * const exp[] = RCU_EXP_NAME_INIT;
+ static const char * const exp_sched[] = RCU_EXP_SCHED_NAME_INIT;
static u8 fl_mask = 0x1;
+
+ int levelcnt[RCU_NUM_LVLS]; /* # nodes in each level. */
+ int levelspread[RCU_NUM_LVLS]; /* kids/node in each level. */
int cpustride = 1;
int i;
int j;
struct rcu_node *rnp;
- BUILD_BUG_ON(MAX_RCU_LVLS > ARRAY_SIZE(buf)); /* Fix buf[] init! */
+ BUILD_BUG_ON(RCU_NUM_LVLS > ARRAY_SIZE(buf)); /* Fix buf[] init! */
/* Silence gcc 4.8 false positive about array index out of range. */
if (rcu_num_lvls <= 0 || rcu_num_lvls > RCU_NUM_LVLS)
@@ -4065,19 +4121,19 @@ static void __init rcu_init_one(struct rcu_state *rsp,
/* Initialize the level-tracking arrays. */
for (i = 0; i < rcu_num_lvls; i++)
- rsp->levelcnt[i] = num_rcu_lvl[i];
+ levelcnt[i] = num_rcu_lvl[i];
for (i = 1; i < rcu_num_lvls; i++)
- rsp->level[i] = rsp->level[i - 1] + rsp->levelcnt[i - 1];
- rcu_init_levelspread(rsp);
+ rsp->level[i] = rsp->level[i - 1] + levelcnt[i - 1];
+ rcu_init_levelspread(levelspread, levelcnt);
rsp->flavor_mask = fl_mask;
fl_mask <<= 1;
/* Initialize the elements themselves, starting from the leaves. */
for (i = rcu_num_lvls - 1; i >= 0; i--) {
- cpustride *= rsp->levelspread[i];
+ cpustride *= levelspread[i];
rnp = rsp->level[i];
- for (j = 0; j < rsp->levelcnt[i]; j++, rnp++) {
+ for (j = 0; j < levelcnt[i]; j++, rnp++) {
raw_spin_lock_init(&rnp->lock);
lockdep_set_class_and_name(&rnp->lock,
&rcu_node_class[i], buf[i]);
@@ -4097,14 +4153,23 @@ static void __init rcu_init_one(struct rcu_state *rsp,
rnp->grpmask = 0;
rnp->parent = NULL;
} else {
- rnp->grpnum = j % rsp->levelspread[i - 1];
+ rnp->grpnum = j % levelspread[i - 1];
rnp->grpmask = 1UL << rnp->grpnum;
rnp->parent = rsp->level[i - 1] +
- j / rsp->levelspread[i - 1];
+ j / levelspread[i - 1];
}
rnp->level = i;
INIT_LIST_HEAD(&rnp->blkd_tasks);
rcu_init_one_nocb(rnp);
+ mutex_init(&rnp->exp_funnel_mutex);
+ if (rsp == &rcu_sched_state)
+ lockdep_set_class_and_name(
+ &rnp->exp_funnel_mutex,
+ &rcu_exp_sched_class[i], exp_sched[i]);
+ else
+ lockdep_set_class_and_name(
+ &rnp->exp_funnel_mutex,
+ &rcu_exp_class[i], exp[i]);
}
}
@@ -4128,9 +4193,7 @@ static void __init rcu_init_geometry(void)
{
ulong d;
int i;
- int j;
- int n = nr_cpu_ids;
- int rcu_capacity[MAX_RCU_LVLS + 1];
+ int rcu_capacity[RCU_NUM_LVLS];
/*
* Initialize any unspecified boot parameters.
@@ -4153,47 +4216,49 @@ static void __init rcu_init_geometry(void)
rcu_fanout_leaf, nr_cpu_ids);
/*
- * Compute number of nodes that can be handled an rcu_node tree
- * with the given number of levels. Setting rcu_capacity[0] makes
- * some of the arithmetic easier.
- */
- rcu_capacity[0] = 1;
- rcu_capacity[1] = rcu_fanout_leaf;
- for (i = 2; i <= MAX_RCU_LVLS; i++)
- rcu_capacity[i] = rcu_capacity[i - 1] * RCU_FANOUT;
-
- /*
* The boot-time rcu_fanout_leaf parameter is only permitted
* to increase the leaf-level fanout, not decrease it. Of course,
* the leaf-level fanout cannot exceed the number of bits in
- * the rcu_node masks. Finally, the tree must be able to accommodate
- * the configured number of CPUs. Complain and fall back to the
- * compile-time values if these limits are exceeded.
+ * the rcu_node masks. Complain and fall back to the compile-
+ * time values if these limits are exceeded.
*/
if (rcu_fanout_leaf < RCU_FANOUT_LEAF ||
- rcu_fanout_leaf > sizeof(unsigned long) * 8 ||
- n > rcu_capacity[MAX_RCU_LVLS]) {
+ rcu_fanout_leaf > sizeof(unsigned long) * 8) {
+ rcu_fanout_leaf = RCU_FANOUT_LEAF;
WARN_ON(1);
return;
}
+ /*
+ * Compute number of nodes that can be handled an rcu_node tree
+ * with the given number of levels.
+ */
+ rcu_capacity[0] = rcu_fanout_leaf;
+ for (i = 1; i < RCU_NUM_LVLS; i++)
+ rcu_capacity[i] = rcu_capacity[i - 1] * RCU_FANOUT;
+
+ /*
+ * The tree must be able to accommodate the configured number of CPUs.
+ * If this limit is exceeded than we have a serious problem elsewhere.
+ */
+ if (nr_cpu_ids > rcu_capacity[RCU_NUM_LVLS - 1])
+ panic("rcu_init_geometry: rcu_capacity[] is too small");
+
+ /* Calculate the number of levels in the tree. */
+ for (i = 0; nr_cpu_ids > rcu_capacity[i]; i++) {
+ }
+ rcu_num_lvls = i + 1;
+
/* Calculate the number of rcu_nodes at each level of the tree. */
- for (i = 1; i <= MAX_RCU_LVLS; i++)
- if (n <= rcu_capacity[i]) {
- for (j = 0; j <= i; j++)
- num_rcu_lvl[j] =
- DIV_ROUND_UP(n, rcu_capacity[i - j]);
- rcu_num_lvls = i;
- for (j = i + 1; j <= MAX_RCU_LVLS; j++)
- num_rcu_lvl[j] = 0;
- break;
- }
+ for (i = 0; i < rcu_num_lvls; i++) {
+ int cap = rcu_capacity[(rcu_num_lvls - 1) - i];
+ num_rcu_lvl[i] = DIV_ROUND_UP(nr_cpu_ids, cap);
+ }
/* Calculate the total number of rcu_node structures. */
rcu_num_nodes = 0;
- for (i = 0; i <= MAX_RCU_LVLS; i++)
+ for (i = 0; i < rcu_num_lvls; i++)
rcu_num_nodes += num_rcu_lvl[i];
- rcu_num_nodes -= n;
}
/*