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rcu: Introduce proper blocking to no-CBs kthreads GP waits

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Currently, the no-CBs kthreads do repeated timed waits for grace periods
to elapse.  This is crude and energy inefficient, so this commit allows
no-CBs kthreads to specify exactly which grace period they are waiting
for and also allows them to block for the entire duration until the
desired grace period completes.

Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
This commit is contained in:
Paul E. McKenney
2013-02-10 20:48:58 -08:00
committed by Paul E. McKenney
parent 911af505ef
commit dae6e64d2b
3 changed files with 127 additions and 20 deletions
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12
kernel/rcutree.h
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@@ -196,6 +196,12 @@ struct rcu_node {
/* Refused to boost: not sure why, though. */
/* This can happen due to race conditions. */
#endif /* #ifdef CONFIG_RCU_BOOST */
#ifdef CONFIG_RCU_NOCB_CPU
wait_queue_head_t nocb_gp_wq[2];
/* Place for rcu_nocb_kthread() to wait GP. */
int n_nocb_gp_requests[2];
/* Counts of upcoming no-CB GP requests. */
#endif /* #ifdef CONFIG_RCU_NOCB_CPU */
raw_spinlock_t fqslock ____cacheline_internodealigned_in_smp;
} ____cacheline_internodealigned_in_smp;
@@ -326,7 +332,6 @@ struct rcu_data {
int nocb_p_count_lazy; /* (approximate). */
wait_queue_head_t nocb_wq; /* For nocb kthreads to sleep on. */
struct task_struct *nocb_kthread;
bool nocb_needs_gp;
#endif /* #ifdef CONFIG_RCU_NOCB_CPU */
int cpu;
@@ -524,7 +529,10 @@ static void print_cpu_stall_info(struct rcu_state *rsp, int cpu);
static void print_cpu_stall_info_end(void);
static void zero_cpu_stall_ticks(struct rcu_data *rdp);
static void increment_cpu_stall_ticks(void);
static int rcu_nocb_needs_gp(struct rcu_data *rdp);
static int rcu_nocb_needs_gp(struct rcu_state *rsp);
static void rcu_nocb_gp_set(struct rcu_node *rnp, int nrq);
static int rcu_nocb_gp_cleanup(struct rcu_state *rsp, struct rcu_node *rnp);
static void rcu_init_one_nocb(struct rcu_node *rnp);
static bool is_nocb_cpu(int cpu);
static bool __call_rcu_nocb(struct rcu_data *rdp, struct rcu_head *rhp,
bool lazy);