linux-kernel - [Patch v4 08/18] sched: Deprecate sched_smt_present and use cpu_smt

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Date:   Tue, 30 Oct 2018 11:49:15 -0700
From:   Tim Chen <tim.c.chen@...ux.intel.com>
To:     Jiri Kosina <jikos@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>
Cc:     Tim Chen <tim.c.chen@...ux.intel.com>,
        Tom Lendacky <thomas.lendacky@....com>,
        Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        David Woodhouse <dwmw@...zon.co.uk>,
        Andi Kleen <ak@...ux.intel.com>,
        Dave Hansen <dave.hansen@...el.com>,
        Casey Schaufler <casey.schaufler@...el.com>,
        Asit Mallick <asit.k.mallick@...el.com>,
        Arjan van de Ven <arjan@...ux.intel.com>,
        Jon Masters <jcm@...hat.com>,
        Waiman Long <longman9394@...il.com>,
        linux-kernel@...r.kernel.org, x86@...nel.org
Subject: [Patch v4 08/18] sched: Deprecate sched_smt_present and use cpu_smt_enabled static key

The cpu_smt_enabled static key serves identical purpose as cpu_smt_enabled
to enable SMT specific code.

This patch replaces sched_smt_present in the scheduler with
cpu_smt_enabled and deprecate sched_smt_present.

Signed-off-by: Tim Chen <tim.c.chen@...ux.intel.com>
---
 kernel/sched/core.c  | 12 ------------
 kernel/sched/fair.c  |  6 ++----
 kernel/sched/sched.h |  4 +---
 3 files changed, 3 insertions(+), 19 deletions(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 625bc98..a06b157 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -5739,18 +5739,6 @@ int sched_cpu_activate(unsigned int cpu)
 	struct rq *rq = cpu_rq(cpu);
 	struct rq_flags rf;
 
-#ifdef CONFIG_SCHED_SMT
-	/*
-	 * The sched_smt_present static key needs to be evaluated on every
-	 * hotplug event because at boot time SMT might be disabled when
-	 * the number of booted CPUs is limited.
-	 *
-	 * If then later a sibling gets hotplugged, then the key would stay
-	 * off and SMT scheduling would never be functional.
-	 */
-	if (cpumask_weight(cpu_smt_mask(cpu)) > 1)
-		static_branch_enable_cpuslocked(&sched_smt_present);
-#endif
 	set_cpu_active(cpu, true);
 
 	if (sched_smp_initialized) {
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index b39fb59..4899bb1 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -5839,8 +5839,6 @@ static inline int find_idlest_cpu(struct sched_domain *sd, struct task_struct *p
 }
 
 #ifdef CONFIG_SCHED_SMT
-DEFINE_STATIC_KEY_FALSE(sched_smt_present);
-
 static inline void set_idle_cores(int cpu, int val)
 {
 	struct sched_domain_shared *sds;
@@ -5900,7 +5898,7 @@ static int select_idle_core(struct task_struct *p, struct sched_domain *sd, int
 	struct cpumask *cpus = this_cpu_cpumask_var_ptr(select_idle_mask);
 	int core, cpu;
 
-	if (!static_branch_likely(&sched_smt_present))
+	if (!static_branch_likely(&cpu_smt_enabled))
 		return -1;
 
 	if (!test_idle_cores(target, false))
@@ -5936,7 +5934,7 @@ static int select_idle_smt(struct task_struct *p, struct sched_domain *sd, int t
 {
 	int cpu;
 
-	if (!static_branch_likely(&sched_smt_present))
+	if (!static_branch_likely(&cpu_smt_enabled))
 		return -1;
 
 	for_each_cpu(cpu, cpu_smt_mask(target)) {
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 4a2e8ca..5adba57 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -928,13 +928,11 @@ static inline int cpu_of(struct rq *rq)
 
 #ifdef CONFIG_SCHED_SMT
 
-extern struct static_key_false sched_smt_present;
-
 extern void __update_idle_core(struct rq *rq);
 
 static inline void update_idle_core(struct rq *rq)
 {
-	if (static_branch_unlikely(&sched_smt_present))
+	if (static_branch_likely(&cpu_smt_enabled))
 		__update_idle_core(rq);
 }
 
-- 
2.9.4