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rcu: Eliminate ->onoff_mutex from rcu_node structure

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Because that RCU grace-period initialization need no longer exclude
CPU-hotplug operations, this commit eliminates the ->onoff_mutex and
its uses.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
This commit is contained in:
Paul E. McKenney 2015-01-23 22:29:37 -08:00
parent 0aa04b055e
commit c199068913
2 changed files with 0 additions and 17 deletions
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15
kernel/rcu/tree.c
View file

@ -101,7 +101,6 @@ struct rcu_state sname##_state = { \
.orphan_nxttail = &sname##_state.orphan_nxtlist, \
.orphan_donetail = &sname##_state.orphan_donelist, \
.barrier_mutex = __MUTEX_INITIALIZER(sname##_state.barrier_mutex), \
.onoff_mutex = __MUTEX_INITIALIZER(sname##_state.onoff_mutex), \
.name = RCU_STATE_NAME(sname), \
.abbr = sabbr, \
}; \
@ -1754,10 +1753,6 @@ static int rcu_gp_init(struct rcu_state *rsp)
trace_rcu_grace_period(rsp->name, rsp->gpnum, TPS("start"));
raw_spin_unlock_irq(&rnp->lock);
/* Exclude any concurrent CPU-hotplug operations. */
mutex_lock(&rsp->onoff_mutex);
smp_mb__after_unlock_lock(); /* ->gpnum increment before GP! */
/*
* Apply per-leaf buffered online and offline operations to the
* rcu_node tree. Note that this new grace period need not wait
@ -1844,7 +1839,6 @@ static int rcu_gp_init(struct rcu_state *rsp)
schedule_timeout_uninterruptible(gp_init_delay);
}
mutex_unlock(&rsp->onoff_mutex);
return 1;
}
@ -2498,9 +2492,6 @@ static void rcu_cleanup_dead_cpu(int cpu, struct rcu_state *rsp)
/* Adjust any no-longer-needed kthreads. */
rcu_boost_kthread_setaffinity(rnp, -1);
/* Exclude any attempts to start a new grace period. */
mutex_lock(&rsp->onoff_mutex);
/* Orphan the dead CPU's callbacks, and adopt them if appropriate. */
raw_spin_lock_irqsave(&rsp->orphan_lock, flags);
rcu_send_cbs_to_orphanage(cpu, rsp, rnp, rdp);
@ -2517,7 +2508,6 @@ static void rcu_cleanup_dead_cpu(int cpu, struct rcu_state *rsp)
WARN_ONCE(rdp->qlen != 0 || rdp->nxtlist != NULL,
"rcu_cleanup_dead_cpu: Callbacks on offline CPU %d: qlen=%lu, nxtlist=%p\n",
cpu, rdp->qlen, rdp->nxtlist);
mutex_unlock(&rsp->onoff_mutex);
}
#else /* #ifdef CONFIG_HOTPLUG_CPU */
@ -3700,9 +3690,6 @@ rcu_init_percpu_data(int cpu, struct rcu_state *rsp)
struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu);
struct rcu_node *rnp = rcu_get_root(rsp);
/* Exclude new grace periods. */
mutex_lock(&rsp->onoff_mutex);
/* Set up local state, ensuring consistent view of global state. */
raw_spin_lock_irqsave(&rnp->lock, flags);
rdp->beenonline = 1; /* We have now been online. */
@ -3733,8 +3720,6 @@ rcu_init_percpu_data(int cpu, struct rcu_state *rsp)
rdp->qs_pending = false;
trace_rcu_grace_period(rsp->name, rdp->gpnum, TPS("cpuonl"));
raw_spin_unlock_irqrestore(&rnp->lock, flags);
mutex_unlock(&rsp->onoff_mutex);
}
static void rcu_prepare_cpu(int cpu)

2
kernel/rcu/tree.h
View file

@ -456,8 +456,6 @@ struct rcu_state {
long qlen; /* Total number of callbacks. */
/* End of fields guarded by orphan_lock. */
struct mutex onoff_mutex; /* Coordinate hotplug & GPs. */
struct mutex barrier_mutex; /* Guards barrier fields. */
atomic_t barrier_cpu_count; /* # CPUs waiting on. */
struct completion barrier_completion; /* Wake at barrier end. */