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authorLinus Torvalds <torvalds@linux-foundation.org>2021-07-04 12:58:33 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2021-07-04 12:58:33 -0700
commit28e92f990337b8b4c5fdec47667f8b96089c503e (patch)
tree0dc55280883e7262d831ad24deb3a4fd2a56031a /kernel/rcu/tree_stall.h
parentda803f82faa5ceeff34aa56c08ceba5384e44e47 (diff)
parent641faf1b9064c270a476a424e60063bb05df3ee9 (diff)
Merge branch 'core-rcu-2021.07.04' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu
Pull RCU updates from Paul McKenney: - Bitmap parsing support for "all" as an alias for all bits - Documentation updates - Miscellaneous fixes, including some that overlap into mm and lockdep - kvfree_rcu() updates - mem_dump_obj() updates, with acks from one of the slab-allocator maintainers - RCU NOCB CPU updates, including limited deoffloading - SRCU updates - Tasks-RCU updates - Torture-test updates * 'core-rcu-2021.07.04' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu: (78 commits) tasks-rcu: Make show_rcu_tasks_gp_kthreads() be static inline rcu-tasks: Make ksoftirqd provide RCU Tasks quiescent states rcu: Add missing __releases() annotation rcu: Remove obsolete rcu_read_unlock() deadlock commentary rcu: Improve comments describing RCU read-side critical sections rcu: Create an unrcu_pointer() to remove __rcu from a pointer srcu: Early test SRCU polling start rcu: Fix various typos in comments rcu/nocb: Unify timers rcu/nocb: Prepare for fine-grained deferred wakeup rcu/nocb: Only cancel nocb timer if not polling rcu/nocb: Delete bypass_timer upon nocb_gp wakeup rcu/nocb: Cancel nocb_timer upon nocb_gp wakeup rcu/nocb: Allow de-offloading rdp leader rcu/nocb: Directly call __wake_nocb_gp() from bypass timer rcu: Don't penalize priority boosting when there is nothing to boost rcu: Point to documentation of ordering guarantees rcu: Make rcu_gp_cleanup() be noinline for tracing rcu: Restrict RCU_STRICT_GRACE_PERIOD to at most four CPUs rcu: Make show_rcu_gp_kthreads() dump rcu_node structures blocking GP ...
Diffstat (limited to 'kernel/rcu/tree_stall.h')
-rw-r--r--kernel/rcu/tree_stall.h84
1 files changed, 76 insertions, 8 deletions
diff --git a/kernel/rcu/tree_stall.h b/kernel/rcu/tree_stall.h
index acb2288063b5..3f937b20814f 100644
--- a/kernel/rcu/tree_stall.h
+++ b/kernel/rcu/tree_stall.h
@@ -314,6 +314,7 @@ static void rcu_print_detail_task_stall_rnp(struct rcu_node *rnp)
* tasks blocked within RCU read-side critical sections.
*/
static int rcu_print_task_stall(struct rcu_node *rnp, unsigned long flags)
+ __releases(rnp->lock)
{
raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
return 0;
@@ -717,6 +718,63 @@ static void check_cpu_stall(struct rcu_data *rdp)
/*
+ * Check to see if a failure to end RCU priority inversion was due to
+ * a CPU not passing through a quiescent state. When this happens, there
+ * is nothing that RCU priority boosting can do to help, so we shouldn't
+ * count this as an RCU priority boosting failure. A return of true says
+ * RCU priority boosting is to blame, and false says otherwise. If false
+ * is returned, the first of the CPUs to blame is stored through cpup.
+ * If there was no CPU blocking the current grace period, but also nothing
+ * in need of being boosted, *cpup is set to -1. This can happen in case
+ * of vCPU preemption while the last CPU is reporting its quiscent state,
+ * for example.
+ *
+ * If cpup is NULL, then a lockless quick check is carried out, suitable
+ * for high-rate usage. On the other hand, if cpup is non-NULL, each
+ * rcu_node structure's ->lock is acquired, ruling out high-rate usage.
+ */
+bool rcu_check_boost_fail(unsigned long gp_state, int *cpup)
+{
+ bool atb = false;
+ int cpu;
+ unsigned long flags;
+ struct rcu_node *rnp;
+
+ rcu_for_each_leaf_node(rnp) {
+ if (!cpup) {
+ if (READ_ONCE(rnp->qsmask)) {
+ return false;
+ } else {
+ if (READ_ONCE(rnp->gp_tasks))
+ atb = true;
+ continue;
+ }
+ }
+ *cpup = -1;
+ raw_spin_lock_irqsave_rcu_node(rnp, flags);
+ if (rnp->gp_tasks)
+ atb = true;
+ if (!rnp->qsmask) {
+ // No CPUs without quiescent states for this rnp.
+ raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
+ continue;
+ }
+ // Find the first holdout CPU.
+ for_each_leaf_node_possible_cpu(rnp, cpu) {
+ if (rnp->qsmask & (1UL << (cpu - rnp->grplo))) {
+ raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
+ *cpup = cpu;
+ return false;
+ }
+ }
+ raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
+ }
+ // Can't blame CPUs, so must blame RCU priority boosting.
+ return atb;
+}
+EXPORT_SYMBOL_GPL(rcu_check_boost_fail);
+
+/*
* Show the state of the grace-period kthreads.
*/
void show_rcu_gp_kthreads(void)
@@ -726,6 +784,7 @@ void show_rcu_gp_kthreads(void)
unsigned long j;
unsigned long ja;
unsigned long jr;
+ unsigned long js;
unsigned long jw;
struct rcu_data *rdp;
struct rcu_node *rnp;
@@ -734,21 +793,30 @@ void show_rcu_gp_kthreads(void)
j = jiffies;
ja = j - data_race(rcu_state.gp_activity);
jr = j - data_race(rcu_state.gp_req_activity);
+ js = j - data_race(rcu_state.gp_start);
jw = j - data_race(rcu_state.gp_wake_time);
- pr_info("%s: wait state: %s(%d) ->state: %#x delta ->gp_activity %lu ->gp_req_activity %lu ->gp_wake_time %lu ->gp_wake_seq %ld ->gp_seq %ld ->gp_seq_needed %ld ->gp_flags %#x\n",
+ pr_info("%s: wait state: %s(%d) ->state: %#lx ->rt_priority %u delta ->gp_start %lu ->gp_activity %lu ->gp_req_activity %lu ->gp_wake_time %lu ->gp_wake_seq %ld ->gp_seq %ld ->gp_seq_needed %ld ->gp_max %lu ->gp_flags %#x\n",
rcu_state.name, gp_state_getname(rcu_state.gp_state),
- rcu_state.gp_state, t ? t->__state : 0x1ffff,
- ja, jr, jw, (long)data_race(rcu_state.gp_wake_seq),
+ rcu_state.gp_state, t ? t->__state : 0x1ffffL, t ? t->rt_priority : 0xffU,
+ js, ja, jr, jw, (long)data_race(rcu_state.gp_wake_seq),
(long)data_race(rcu_state.gp_seq),
(long)data_race(rcu_get_root()->gp_seq_needed),
+ data_race(rcu_state.gp_max),
data_race(rcu_state.gp_flags));
rcu_for_each_node_breadth_first(rnp) {
- if (ULONG_CMP_GE(READ_ONCE(rcu_state.gp_seq),
- READ_ONCE(rnp->gp_seq_needed)))
+ if (ULONG_CMP_GE(READ_ONCE(rcu_state.gp_seq), READ_ONCE(rnp->gp_seq_needed)) &&
+ !data_race(rnp->qsmask) && !data_race(rnp->boost_tasks) &&
+ !data_race(rnp->exp_tasks) && !data_race(rnp->gp_tasks))
continue;
- pr_info("\trcu_node %d:%d ->gp_seq %ld ->gp_seq_needed %ld\n",
- rnp->grplo, rnp->grphi, (long)data_race(rnp->gp_seq),
- (long)data_race(rnp->gp_seq_needed));
+ pr_info("\trcu_node %d:%d ->gp_seq %ld ->gp_seq_needed %ld ->qsmask %#lx %c%c%c%c ->n_boosts %ld\n",
+ rnp->grplo, rnp->grphi,
+ (long)data_race(rnp->gp_seq), (long)data_race(rnp->gp_seq_needed),
+ data_race(rnp->qsmask),
+ ".b"[!!data_race(rnp->boost_kthread_task)],
+ ".B"[!!data_race(rnp->boost_tasks)],
+ ".E"[!!data_race(rnp->exp_tasks)],
+ ".G"[!!data_race(rnp->gp_tasks)],
+ data_race(rnp->n_boosts));
if (!rcu_is_leaf_node(rnp))
continue;
for_each_leaf_node_possible_cpu(rnp, cpu) {