From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753370AbbJFQcE (ORCPT ); Tue, 6 Oct 2015 12:32:04 -0400 Received: from e31.co.us.ibm.com ([32.97.110.149]:42841 "EHLO e31.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752888AbbJFQ3t (ORCPT ); Tue, 6 Oct 2015 12:29:49 -0400 X-IBM-Helo: d03dlp03.boulder.ibm.com X-IBM-MailFrom: paulmck@linux.vnet.ibm.com X-IBM-RcptTo: linux-kernel@vger.kernel.org From: "Paul E. McKenney" To: linux-kernel@vger.kernel.org Cc: mingo@kernel.org, jiangshanlai@gmail.com, dipankar@in.ibm.com, akpm@linux-foundation.org, mathieu.desnoyers@efficios.com, josh@joshtriplett.org, tglx@linutronix.de, peterz@infradead.org, rostedt@goodmis.org, dhowells@redhat.com, edumazet@google.com, dvhart@linux.intel.com, fweisbec@gmail.com, oleg@redhat.com, bobby.prani@gmail.com, "Paul E. McKenney" Subject: [PATCH tip/core/rcu 08/18] rcu: Make ->cpu_no_qs be a union for aggregate OR Date: Tue, 6 Oct 2015 09:29:27 -0700 Message-Id: <1444148977-14108-8-git-send-email-paulmck@linux.vnet.ibm.com> X-Mailer: git-send-email 2.5.2 In-Reply-To: <1444148977-14108-1-git-send-email-paulmck@linux.vnet.ibm.com> References: <20151006162907.GA12020@linux.vnet.ibm.com> <1444148977-14108-1-git-send-email-paulmck@linux.vnet.ibm.com> X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 15100616-8236-0000-0000-000012790D16 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This commit converts the rcu_data structure's ->cpu_no_qs field to a union. The bytewise side of this union allows individual access to indications as to whether this CPU needs to find a quiescent state for a normal (.norm) and/or expedited (.exp) grace period. The setwise side of the union allows testing whether or not a quiescent state is needed at all, for either type of grace period. For now, only .norm is used. A later commit will introduce the expedited usage. Signed-off-by: Paul E. McKenney --- kernel/rcu/tree.c | 22 +++++++++++----------- kernel/rcu/tree.h | 14 +++++++++++++- kernel/rcu/tree_plugin.h | 6 +++--- kernel/rcu/tree_trace.c | 2 +- 4 files changed, 28 insertions(+), 16 deletions(-) diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index 31e7021ced4d..3e2875b38eae 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -245,21 +245,21 @@ static int rcu_gp_in_progress(struct rcu_state *rsp) */ void rcu_sched_qs(void) { - if (__this_cpu_read(rcu_sched_data.cpu_no_qs)) { + if (__this_cpu_read(rcu_sched_data.cpu_no_qs.s)) { trace_rcu_grace_period(TPS("rcu_sched"), __this_cpu_read(rcu_sched_data.gpnum), TPS("cpuqs")); - __this_cpu_write(rcu_sched_data.cpu_no_qs, false); + __this_cpu_write(rcu_sched_data.cpu_no_qs.b.norm, false); } } void rcu_bh_qs(void) { - if (__this_cpu_read(rcu_bh_data.cpu_no_qs)) { + if (__this_cpu_read(rcu_bh_data.cpu_no_qs.s)) { trace_rcu_grace_period(TPS("rcu_bh"), __this_cpu_read(rcu_bh_data.gpnum), TPS("cpuqs")); - __this_cpu_write(rcu_bh_data.cpu_no_qs, false); + __this_cpu_write(rcu_bh_data.cpu_no_qs.b.norm, false); } } @@ -1744,7 +1744,7 @@ static bool __note_gp_changes(struct rcu_state *rsp, struct rcu_node *rnp, */ rdp->gpnum = rnp->gpnum; trace_rcu_grace_period(rsp->name, rdp->gpnum, TPS("cpustart")); - rdp->cpu_no_qs = true; + rdp->cpu_no_qs.b.norm = true; rdp->rcu_qs_ctr_snap = __this_cpu_read(rcu_qs_ctr); rdp->core_needs_qs = !!(rnp->qsmask & rdp->grpmask); zero_cpu_stall_ticks(rdp); @@ -2337,7 +2337,7 @@ rcu_report_qs_rdp(int cpu, struct rcu_state *rsp, struct rcu_data *rdp) rnp = rdp->mynode; raw_spin_lock_irqsave(&rnp->lock, flags); smp_mb__after_unlock_lock(); - if ((rdp->cpu_no_qs && + if ((rdp->cpu_no_qs.b.norm && rdp->rcu_qs_ctr_snap == __this_cpu_read(rcu_qs_ctr)) || rdp->gpnum != rnp->gpnum || rnp->completed == rnp->gpnum || rdp->gpwrap) { @@ -2348,7 +2348,7 @@ rcu_report_qs_rdp(int cpu, struct rcu_state *rsp, struct rcu_data *rdp) * We will instead need a new quiescent state that lies * within the current grace period. */ - rdp->cpu_no_qs = true; /* need qs for new gp. */ + rdp->cpu_no_qs.b.norm = true; /* need qs for new gp. */ rdp->rcu_qs_ctr_snap = __this_cpu_read(rcu_qs_ctr); raw_spin_unlock_irqrestore(&rnp->lock, flags); return; @@ -2395,7 +2395,7 @@ rcu_check_quiescent_state(struct rcu_state *rsp, struct rcu_data *rdp) * Was there a quiescent state since the beginning of the grace * period? If no, then exit and wait for the next call. */ - if (rdp->cpu_no_qs && + if (rdp->cpu_no_qs.b.norm && rdp->rcu_qs_ctr_snap == __this_cpu_read(rcu_qs_ctr)) return; @@ -3828,11 +3828,11 @@ static int __rcu_pending(struct rcu_state *rsp, struct rcu_data *rdp) /* Is the RCU core waiting for a quiescent state from this CPU? */ if (rcu_scheduler_fully_active && - rdp->core_needs_qs && rdp->cpu_no_qs && + rdp->core_needs_qs && rdp->cpu_no_qs.b.norm && rdp->rcu_qs_ctr_snap == __this_cpu_read(rcu_qs_ctr)) { rdp->n_rp_core_needs_qs++; } else if (rdp->core_needs_qs && - (!rdp->cpu_no_qs || + (!rdp->cpu_no_qs.b.norm || rdp->rcu_qs_ctr_snap != __this_cpu_read(rcu_qs_ctr))) { rdp->n_rp_report_qs++; return 1; @@ -4155,7 +4155,7 @@ rcu_init_percpu_data(int cpu, struct rcu_state *rsp) rdp->beenonline = true; /* We have now been online. */ rdp->gpnum = rnp->completed; /* Make CPU later note any new GP. */ rdp->completed = rnp->completed; - rdp->cpu_no_qs = true; + rdp->cpu_no_qs.b.norm = true; rdp->rcu_qs_ctr_snap = per_cpu(rcu_qs_ctr, cpu); rdp->core_needs_qs = false; trace_rcu_grace_period(rsp->name, rdp->gpnum, TPS("cpuonl")); diff --git a/kernel/rcu/tree.h b/kernel/rcu/tree.h index ded4ceebed76..3eee48bcf52b 100644 --- a/kernel/rcu/tree.h +++ b/kernel/rcu/tree.h @@ -286,6 +286,18 @@ struct rcu_node { for ((rnp) = (rsp)->level[rcu_num_lvls - 1]; \ (rnp) < &(rsp)->node[rcu_num_nodes]; (rnp)++) +/* + * Union to allow "aggregate OR" operation on the need for a quiescent + * state by the normal and expedited grace periods. + */ +union rcu_noqs { + struct { + u8 norm; + u8 exp; + } b; /* Bits. */ + u16 s; /* Set of bits, aggregate OR here. */ +}; + /* Index values for nxttail array in struct rcu_data. */ #define RCU_DONE_TAIL 0 /* Also RCU_WAIT head. */ #define RCU_WAIT_TAIL 1 /* Also RCU_NEXT_READY head. */ @@ -302,7 +314,7 @@ struct rcu_data { /* is aware of having started. */ unsigned long rcu_qs_ctr_snap;/* Snapshot of rcu_qs_ctr to check */ /* for rcu_all_qs() invocations. */ - bool cpu_no_qs; /* No QS yet for this CPU. */ + union rcu_noqs cpu_no_qs; /* No QSes yet for this CPU. */ bool core_needs_qs; /* Core waits for quiesc state. */ bool beenonline; /* CPU online at least once. */ bool gpwrap; /* Possible gpnum/completed wrap. */ diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h index 6977ff0dccb9..7880202f1e38 100644 --- a/kernel/rcu/tree_plugin.h +++ b/kernel/rcu/tree_plugin.h @@ -265,11 +265,11 @@ static void rcu_preempt_ctxt_queue(struct rcu_node *rnp, struct rcu_data *rdp, */ static void rcu_preempt_qs(void) { - if (__this_cpu_read(rcu_data_p->cpu_no_qs)) { + if (__this_cpu_read(rcu_data_p->cpu_no_qs.s)) { trace_rcu_grace_period(TPS("rcu_preempt"), __this_cpu_read(rcu_data_p->gpnum), TPS("cpuqs")); - __this_cpu_write(rcu_data_p->cpu_no_qs, false); + __this_cpu_write(rcu_data_p->cpu_no_qs.b.norm, false); barrier(); /* Coordinate with rcu_preempt_check_callbacks(). */ current->rcu_read_unlock_special.b.need_qs = false; } @@ -620,7 +620,7 @@ static void rcu_preempt_check_callbacks(void) } if (t->rcu_read_lock_nesting > 0 && __this_cpu_read(rcu_data_p->core_needs_qs) && - __this_cpu_read(rcu_data_p->cpu_no_qs)) + __this_cpu_read(rcu_data_p->cpu_no_qs.b.norm)) t->rcu_read_unlock_special.b.need_qs = true; } diff --git a/kernel/rcu/tree_trace.c b/kernel/rcu/tree_trace.c index d373e57109b8..999c3672f990 100644 --- a/kernel/rcu/tree_trace.c +++ b/kernel/rcu/tree_trace.c @@ -121,7 +121,7 @@ static void print_one_rcu_data(struct seq_file *m, struct rcu_data *rdp) rdp->cpu, cpu_is_offline(rdp->cpu) ? '!' : ' ', ulong2long(rdp->completed), ulong2long(rdp->gpnum), - rdp->cpu_no_qs, + rdp->cpu_no_qs.b.norm, rdp->rcu_qs_ctr_snap == per_cpu(rcu_qs_ctr, rdp->cpu), rdp->core_needs_qs); seq_printf(m, " dt=%d/%llx/%d df=%lu", -- 2.5.2