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authorPaul E. McKenney <paulmck@linux.vnet.ibm.com>2015-06-25 16:30:54 -0700
committerPaul E. McKenney <paulmck@linux.vnet.ibm.com>2015-07-17 14:58:53 -0700
commitb09e5f8601d7e5b8d45348c9c09e1fb4109e8dc6 (patch)
treea1bdf6c42233e52852a14329dd2da6d1bb4fc2a7 /kernel/rcu
parent543c6158f6dff20a741dfa492771f18ceaa1a109 (diff)
downloadblackbird-op-linux-b09e5f8601d7e5b8d45348c9c09e1fb4109e8dc6.tar.gz
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rcu: Abstract funnel locking from synchronize_sched_expedited()
This commit abstracts funnel locking from synchronize_sched_expedited() so that it may be used by synchronize_rcu_expedited(). Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Diffstat (limited to 'kernel/rcu')
-rw-r--r--kernel/rcu/tree.c80
1 files changed, 47 insertions, 33 deletions
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 67fe75725486..f79a1c646846 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -3309,16 +3309,6 @@ static bool rcu_exp_gp_seq_done(struct rcu_state *rsp, unsigned long s)
return rcu_seq_done(&rsp->expedited_sequence, s);
}
-static int synchronize_sched_expedited_cpu_stop(void *data)
-{
- struct rcu_state *rsp = data;
-
- /* We are here: If we are last, do the wakeup. */
- if (atomic_dec_and_test(&rsp->expedited_need_qs))
- wake_up(&rsp->expedited_wq);
- return 0;
-}
-
/* Common code for synchronize_sched_expedited() work-done checking. */
static bool sync_sched_exp_wd(struct rcu_state *rsp, struct rcu_node *rnp,
atomic_long_t *stat, unsigned long s)
@@ -3335,6 +3325,48 @@ static bool sync_sched_exp_wd(struct rcu_state *rsp, struct rcu_node *rnp,
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_node *rnp0;
+ struct rcu_node *rnp1 = NULL;
+
+ /*
+ * 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.
+ */
+ rnp0 = per_cpu_ptr(rsp->rda, raw_smp_processor_id())->mynode;
+ for (; rnp0 != NULL; rnp0 = rnp0->parent) {
+ if (sync_sched_exp_wd(rsp, rnp1, &rsp->expedited_workdone1, s))
+ return NULL;
+ mutex_lock(&rnp0->exp_funnel_mutex);
+ if (rnp1)
+ mutex_unlock(&rnp1->exp_funnel_mutex);
+ rnp1 = rnp0;
+ }
+ if (sync_sched_exp_wd(rsp, rnp1, &rsp->expedited_workdone2, s))
+ return NULL;
+ return rnp1;
+}
+
+static int synchronize_sched_expedited_cpu_stop(void *data)
+{
+ struct rcu_state *rsp = data;
+
+ /* We are here: If we are last, do the wakeup. */
+ if (atomic_dec_and_test(&rsp->expedited_need_qs))
+ wake_up(&rsp->expedited_wq);
+ return 0;
+}
+
/**
* synchronize_sched_expedited - Brute-force RCU-sched grace period
*
@@ -3355,8 +3387,7 @@ void synchronize_sched_expedited(void)
{
int cpu;
long s;
- struct rcu_node *rnp0;
- struct rcu_node *rnp1 = NULL;
+ struct rcu_node *rnp;
struct rcu_state *rsp = &rcu_sched_state;
/* Take a snapshot of the sequence number. */
@@ -3370,26 +3401,9 @@ void synchronize_sched_expedited(void)
}
WARN_ON_ONCE(cpu_is_offline(raw_smp_processor_id()));
- /*
- * 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.
- */
- rnp0 = per_cpu_ptr(rsp->rda, raw_smp_processor_id())->mynode;
- for (; rnp0 != NULL; rnp0 = rnp0->parent) {
- if (sync_sched_exp_wd(rsp, rnp1, &rsp->expedited_workdone1, s))
- return;
- mutex_lock(&rnp0->exp_funnel_mutex);
- if (rnp1)
- mutex_unlock(&rnp1->exp_funnel_mutex);
- rnp1 = rnp0;
- }
- rnp0 = rnp1; /* rcu_get_root(rsp), AKA root rcu_node structure. */
- if (sync_sched_exp_wd(rsp, rnp0, &rsp->expedited_workdone2, s))
- return;
+ rnp = exp_funnel_lock(rsp, s);
+ if (rnp == NULL)
+ return; /* Someone else did our work for us. */
rcu_exp_gp_seq_start(rsp);
@@ -3415,7 +3429,7 @@ void synchronize_sched_expedited(void)
!atomic_read(&rsp->expedited_need_qs));
rcu_exp_gp_seq_end(rsp);
- mutex_unlock(&rnp0->exp_funnel_mutex);
+ mutex_unlock(&rnp->exp_funnel_mutex);
smp_mb(); /* ensure subsequent action seen after grace period. */
put_online_cpus();
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