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author | Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2015-06-25 16:30:54 -0700 |
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committer | Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2015-07-17 14:58:53 -0700 |
commit | b09e5f8601d7e5b8d45348c9c09e1fb4109e8dc6 (patch) | |
tree | a1bdf6c42233e52852a14329dd2da6d1bb4fc2a7 /kernel/rcu/tree.c | |
parent | 543c6158f6dff20a741dfa492771f18ceaa1a109 (diff) | |
download | op-kernel-dev-b09e5f8601d7e5b8d45348c9c09e1fb4109e8dc6.zip op-kernel-dev-b09e5f8601d7e5b8d45348c9c09e1fb4109e8dc6.tar.gz |
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/tree.c')
-rw-r--r-- | kernel/rcu/tree.c | 80 |
1 files changed, 47 insertions, 33 deletions
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index 67fe757..f79a1c6 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(); |