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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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21
kernel/rcu/tree_trace.c
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@@ -41,6 +41,7 @@
#include <linux/mutex.h>
#include <linux/debugfs.h>
#include <linux/seq_file.h>
#include <linux/prefetch.h>
#define RCU_TREE_NONCORE
#include "tree.h"
@@ -128,17 +129,15 @@ static void print_one_rcu_data(struct seq_file *m, struct rcu_data *rdp)
rdp->dynticks_fqs);
seq_printf(m, " of=%lu", rdp->offline_fqs);
rcu_nocb_q_lengths(rdp, &ql, &qll);
qll += rdp->qlen_lazy;
ql += rdp->qlen;
qll += rcu_segcblist_n_lazy_cbs(&rdp->cblist);
ql += rcu_segcblist_n_cbs(&rdp->cblist);
seq_printf(m, " ql=%ld/%ld qs=%c%c%c%c",
qll, ql,
".N"[rdp->nxttail[RCU_NEXT_READY_TAIL] !=
rdp->nxttail[RCU_NEXT_TAIL]],
".R"[rdp->nxttail[RCU_WAIT_TAIL] !=
rdp->nxttail[RCU_NEXT_READY_TAIL]],
".W"[rdp->nxttail[RCU_DONE_TAIL] !=
rdp->nxttail[RCU_WAIT_TAIL]],
".D"[&rdp->nxtlist != rdp->nxttail[RCU_DONE_TAIL]]);
".N"[!rcu_segcblist_segempty(&rdp->cblist, RCU_NEXT_TAIL)],
".R"[!rcu_segcblist_segempty(&rdp->cblist,
RCU_NEXT_READY_TAIL)],
".W"[!rcu_segcblist_segempty(&rdp->cblist, RCU_WAIT_TAIL)],
".D"[!rcu_segcblist_segempty(&rdp->cblist, RCU_DONE_TAIL)]);
#ifdef CONFIG_RCU_BOOST
seq_printf(m, " kt=%d/%c ktl=%x",
per_cpu(rcu_cpu_has_work, rdp->cpu),
@@ -276,7 +275,9 @@ static void print_one_rcu_state(struct seq_file *m, struct rcu_state *rsp)
seq_printf(m, "nfqs=%lu/nfqsng=%lu(%lu) fqlh=%lu oqlen=%ld/%ld\n",
rsp->n_force_qs, rsp->n_force_qs_ngp,
rsp->n_force_qs - rsp->n_force_qs_ngp,
READ_ONCE(rsp->n_force_qs_lh), rsp->qlen_lazy, rsp->qlen);
READ_ONCE(rsp->n_force_qs_lh),
rcu_cblist_n_lazy_cbs(&rsp->orphan_done),
rcu_cblist_n_cbs(&rsp->orphan_done));
for (rnp = &rsp->node[0]; rnp - &rsp->node[0] < rcu_num_nodes; rnp++) {
if (rnp->level != level) {
seq_puts(m, "\n");