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sched: Add sched_smt_active()

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Add the sched_smt_active() function needed for some x86 speculation
mitigations.  This was introduced upstream by commits 1b568f0aabf2
"sched/core: Optimize SCHED_SMT", ba2591a5993e "sched/smt: Update
sched_smt_present at runtime", c5511d03ec09 "sched/smt: Make
sched_smt_present track topology", and 321a874a7ef8 "sched/smt: Expose
sched_smt_present static key".  The upstream implementation uses the
static_key_{disable,enable}_cpuslocked() functions, which aren't
practical to backport.

Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Ben Hutchings 2019-05-10 00:46:25 +01:00 committed by Greg Kroah-Hartman
parent f576a78075
commit 1f562beba7
3 changed files with 43 additions and 0 deletions
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18
include/linux/sched/smt.h Normal file
View File

@ -0,0 +1,18 @@
/* SPDX-License-Identifier: GPL-2.0 */
#ifndef _LINUX_SCHED_SMT_H
#define _LINUX_SCHED_SMT_H
#include <linux/atomic.h>
#ifdef CONFIG_SCHED_SMT
extern atomic_t sched_smt_present;
static __always_inline bool sched_smt_active(void)
{
return atomic_read(&sched_smt_present);
}
#else
static inline bool sched_smt_active(void) { return false; }
#endif
#endif

24
kernel/sched/core.c
View File

@ -5610,6 +5610,10 @@ static void set_cpu_rq_start_time(void)
rq->age_stamp = sched_clock_cpu(cpu);
}
#ifdef CONFIG_SCHED_SMT
atomic_t sched_smt_present = ATOMIC_INIT(0);
#endif
static int sched_cpu_active(struct notifier_block *nfb,
unsigned long action, void *hcpu)
{
@ -5626,11 +5630,23 @@ static int sched_cpu_active(struct notifier_block *nfb,
* set_cpu_online(). But it might not yet have marked itself
* as active, which is essential from here on.
*/
#ifdef CONFIG_SCHED_SMT
/*
* When going up, increment the number of cores with SMT present.
*/
if (cpumask_weight(cpu_smt_mask(cpu)) == 2)
atomic_inc(&sched_smt_present);
#endif
set_cpu_active(cpu, true);
stop_machine_unpark(cpu);
return NOTIFY_OK;
case CPU_DOWN_FAILED:
#ifdef CONFIG_SCHED_SMT
/* Same as for CPU_ONLINE */
if (cpumask_weight(cpu_smt_mask(cpu)) == 2)
atomic_inc(&sched_smt_present);
#endif
set_cpu_active(cpu, true);
return NOTIFY_OK;
@ -5645,7 +5661,15 @@ static int sched_cpu_inactive(struct notifier_block *nfb,
switch (action & ~CPU_TASKS_FROZEN) {
case CPU_DOWN_PREPARE:
set_cpu_active((long)hcpu, false);
#ifdef CONFIG_SCHED_SMT
/*
* When going down, decrement the number of cores with SMT present.
*/
if (cpumask_weight(cpu_smt_mask((long)hcpu)) == 2)
atomic_dec(&sched_smt_present);
#endif
return NOTIFY_OK;
default:
return NOTIFY_DONE;
}

1
kernel/sched/sched.h
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@ -2,6 +2,7 @@
#include <linux/sched.h>
#include <linux/sched/sysctl.h>
#include <linux/sched/rt.h>
#include <linux/sched/smt.h>
#include <linux/sched/deadline.h>
#include <linux/mutex.h>
#include <linux/spinlock.h>