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srcu: Abstract multi-tail callback list handling

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RCU has only one multi-tail callback list, which is implemented via
the nxtlist, nxttail, nxtcompleted, qlen_lazy, and qlen fields in the
rcu_data structure, and whose operations are open-code throughout the
Tree RCU implementation.  This has been more or less OK in the past,
but upcoming callback-list optimizations in SRCU could really use
a multi-tail callback list there as well.

This commit therefore abstracts the multi-tail callback list handling
into a new kernel/rcu/rcu_segcblist.h file, and uses this new API.
The simple head-and-tail pointer callback list is also abstracted and
applied everywhere except for the NOCB callback-offload lists.  (Yes,
the plan is to apply them there as well, but this commit is already
bigger than would be good.)

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
This commit is contained in:
Paul E. McKenney 2017-02-08 12:36:42 -08:00
parent b8c78d3afc
commit 15fecf89e4
5 changed files with 780 additions and 309 deletions
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54
kernel/rcu/tree_plugin.h
View file

@ -1350,10 +1350,10 @@ static bool __maybe_unused rcu_try_advance_all_cbs(void)
*/
if ((rdp->completed != rnp->completed ||
unlikely(READ_ONCE(rdp->gpwrap))) &&
rdp->nxttail[RCU_DONE_TAIL] != rdp->nxttail[RCU_NEXT_TAIL])
rcu_segcblist_pend_cbs(&rdp->cblist))
note_gp_changes(rsp, rdp);
if (cpu_has_callbacks_ready_to_invoke(rdp))
if (rcu_segcblist_ready_cbs(&rdp->cblist))
cbs_ready = true;
}
return cbs_ready;
@ -1461,7 +1461,7 @@ static void rcu_prepare_for_idle(void)
rdtp->last_accelerate = jiffies;
for_each_rcu_flavor(rsp) {
rdp = this_cpu_ptr(rsp->rda);
if (!*rdp->nxttail[RCU_DONE_TAIL])
if (rcu_segcblist_pend_cbs(&rdp->cblist))
continue;
rnp = rdp->mynode;
raw_spin_lock_rcu_node(rnp); /* irqs already disabled. */
@ -1529,7 +1529,7 @@ static void rcu_oom_notify_cpu(void *unused)
for_each_rcu_flavor(rsp) {
rdp = raw_cpu_ptr(rsp->rda);
if (rdp->qlen_lazy != 0) {
if (rcu_segcblist_n_lazy_cbs(&rdp->cblist)) {
atomic_inc(&oom_callback_count);
rsp->call(&rdp->oom_head, rcu_oom_callback);
}
@ -1934,30 +1934,26 @@ static bool __maybe_unused rcu_nocb_adopt_orphan_cbs(struct rcu_state *rsp,
struct rcu_data *rdp,
unsigned long flags)
{
long ql = rsp->qlen;
long qll = rsp->qlen_lazy;
long ql = rcu_cblist_n_cbs(&rsp->orphan_done);
long qll = rcu_cblist_n_lazy_cbs(&rsp->orphan_done);
/* If this is not a no-CBs CPU, tell the caller to do it the old way. */
if (!rcu_is_nocb_cpu(smp_processor_id()))
return false;
rsp->qlen = 0;
rsp->qlen_lazy = 0;
/* First, enqueue the donelist, if any. This preserves CB ordering. */
if (rsp->orphan_donelist != NULL) {
__call_rcu_nocb_enqueue(rdp, rsp->orphan_donelist,
rsp->orphan_donetail, ql, qll, flags);
ql = qll = 0;
rsp->orphan_donelist = NULL;
rsp->orphan_donetail = &rsp->orphan_donelist;
if (!rcu_cblist_empty(&rsp->orphan_done)) {
__call_rcu_nocb_enqueue(rdp, rcu_cblist_head(&rsp->orphan_done),
rcu_cblist_tail(&rsp->orphan_done),
ql, qll, flags);
}
if (rsp->orphan_nxtlist != NULL) {
__call_rcu_nocb_enqueue(rdp, rsp->orphan_nxtlist,
rsp->orphan_nxttail, ql, qll, flags);
ql = qll = 0;
rsp->orphan_nxtlist = NULL;
rsp->orphan_nxttail = &rsp->orphan_nxtlist;
if (!rcu_cblist_empty(&rsp->orphan_pend)) {
__call_rcu_nocb_enqueue(rdp, rcu_cblist_head(&rsp->orphan_pend),
rcu_cblist_tail(&rsp->orphan_pend),
ql, qll, flags);
}
rcu_cblist_init(&rsp->orphan_done);
rcu_cblist_init(&rsp->orphan_pend);
return true;
}
@ -2399,16 +2395,16 @@ static bool init_nocb_callback_list(struct rcu_data *rdp)
return false;
/* If there are early-boot callbacks, move them to nocb lists. */
if (rdp->nxtlist) {
rdp->nocb_head = rdp->nxtlist;
rdp->nocb_tail = rdp->nxttail[RCU_NEXT_TAIL];
atomic_long_set(&rdp->nocb_q_count, rdp->qlen);
atomic_long_set(&rdp->nocb_q_count_lazy, rdp->qlen_lazy);
rdp->nxtlist = NULL;
rdp->qlen = 0;
rdp->qlen_lazy = 0;
if (!rcu_segcblist_empty(&rdp->cblist)) {
rdp->nocb_head = rcu_segcblist_head(&rdp->cblist);
rdp->nocb_tail = rcu_segcblist_tail(&rdp->cblist);
atomic_long_set(&rdp->nocb_q_count,
rcu_segcblist_n_cbs(&rdp->cblist));
atomic_long_set(&rdp->nocb_q_count_lazy,
rcu_segcblist_n_lazy_cbs(&rdp->cblist));
rcu_segcblist_init(&rdp->cblist);
}
rdp->nxttail[RCU_NEXT_TAIL] = NULL;
rcu_segcblist_disable(&rdp->cblist);
return true;
}