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From: Julien Thierry <julien.thierry@arm.com>
To: linux-arm-kernel@lists.infradead.org
Cc: mark.rutland@arm.com, Julien Thierry <julien.thierry@arm.com>,
	peterz@infradead.org, jolsa@redhat.com, will.deacon@arm.com,
	Russell King <linux@armlinux.org.uk>,
	acme@kernel.org, alexander.shishkin@linux.intel.com,
	mingo@redhat.com, namhyung@kernel.org, sthotton@marvell.com,
	liwei391@huawei.com
Subject: [PATCH v4 4/9] arm: perf: Remove Remove PMU locking
Date: Wed, 17 Jul 2019 09:17:07 +0100
Message-ID: <1563351432-55652-5-git-send-email-julien.thierry@arm.com> (raw)
In-Reply-To: <1563351432-55652-1-git-send-email-julien.thierry@arm.com>

Since the PMU interrupt saves and restores the value of the selector
register, there is no need to serialize register accesses against the
interrupt contexts.

For operations that can be called with interrupts enabled, preemption
still needs to be disabled to ensure the programming of the PMU is
done on the expected CPU and not migrated mid-programming.

Signed-off-by: Julien Thierry <julien.thierry@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Russell King <linux@armlinux.org.uk>
---
 arch/arm/kernel/perf_event_v7.c | 54 ++---------------------------------------
 1 file changed, 2 insertions(+), 52 deletions(-)

diff --git a/arch/arm/kernel/perf_event_v7.c b/arch/arm/kernel/perf_event_v7.c
index b7be2a3..9655127 100644
--- a/arch/arm/kernel/perf_event_v7.c
+++ b/arch/arm/kernel/perf_event_v7.c
@@ -882,10 +882,8 @@ static void armv7_pmnc_dump_regs(struct arm_pmu *cpu_pmu)

 static void armv7pmu_enable_event(struct perf_event *event)
 {
-	unsigned long flags;
 	struct hw_perf_event *hwc = &event->hw;
 	struct arm_pmu *cpu_pmu = to_arm_pmu(event->pmu);
-	struct pmu_hw_events *events = this_cpu_ptr(cpu_pmu->hw_events);
 	int idx = hwc->idx;

 	if (!armv7_pmnc_counter_valid(cpu_pmu, idx)) {
@@ -898,7 +896,6 @@ static void armv7pmu_enable_event(struct perf_event *event)
 	 * Enable counter and interrupt, and set the counter to count
 	 * the event that we're interested in.
 	 */
-	raw_spin_lock_irqsave(&events->pmu_lock, flags);

 	/*
 	 * Disable counter
@@ -922,16 +919,12 @@ static void armv7pmu_enable_event(struct perf_event *event)
 	 * Enable counter
 	 */
 	armv7_pmnc_enable_counter(idx);
-
-	raw_spin_unlock_irqrestore(&events->pmu_lock, flags);
 }

 static void armv7pmu_disable_event(struct perf_event *event)
 {
-	unsigned long flags;
 	struct hw_perf_event *hwc = &event->hw;
 	struct arm_pmu *cpu_pmu = to_arm_pmu(event->pmu);
-	struct pmu_hw_events *events = this_cpu_ptr(cpu_pmu->hw_events);
 	int idx = hwc->idx;

 	if (!armv7_pmnc_counter_valid(cpu_pmu, idx)) {
@@ -941,11 +934,6 @@ static void armv7pmu_disable_event(struct perf_event *event)
 	}

 	/*
-	 * Disable counter and interrupt
-	 */
-	raw_spin_lock_irqsave(&events->pmu_lock, flags);
-
-	/*
 	 * Disable counter
 	 */
 	armv7_pmnc_disable_counter(idx);
@@ -954,8 +942,6 @@ static void armv7pmu_disable_event(struct perf_event *event)
 	 * Disable interrupt for this counter
 	 */
 	armv7_pmnc_disable_intens(idx);
-
-	raw_spin_unlock_irqrestore(&events->pmu_lock, flags);
 }

 static irqreturn_t armv7pmu_handle_irq(struct arm_pmu *cpu_pmu)
@@ -1030,24 +1016,16 @@ static irqreturn_t armv7pmu_handle_irq(struct arm_pmu *cpu_pmu)

 static void armv7pmu_start(struct arm_pmu *cpu_pmu)
 {
-	unsigned long flags;
-	struct pmu_hw_events *events = this_cpu_ptr(cpu_pmu->hw_events);
-
-	raw_spin_lock_irqsave(&events->pmu_lock, flags);
+	WARN_ON_ONCE(preemptible());
 	/* Enable all counters */
 	armv7_pmnc_write(armv7_pmnc_read() | ARMV7_PMNC_E);
-	raw_spin_unlock_irqrestore(&events->pmu_lock, flags);
 }

 static void armv7pmu_stop(struct arm_pmu *cpu_pmu)
 {
-	unsigned long flags;
-	struct pmu_hw_events *events = this_cpu_ptr(cpu_pmu->hw_events);
-
-	raw_spin_lock_irqsave(&events->pmu_lock, flags);
+	WARN_ON_ONCE(preemptible());
 	/* Disable all counters */
 	armv7_pmnc_write(armv7_pmnc_read() & ~ARMV7_PMNC_E);
-	raw_spin_unlock_irqrestore(&events->pmu_lock, flags);
 }

 static int armv7pmu_get_event_idx(struct pmu_hw_events *cpuc,
@@ -1513,14 +1491,8 @@ static void krait_clearpmu(u32 config_base)

 static void krait_pmu_disable_event(struct perf_event *event)
 {
-	unsigned long flags;
 	struct hw_perf_event *hwc = &event->hw;
 	int idx = hwc->idx;
-	struct arm_pmu *cpu_pmu = to_arm_pmu(event->pmu);
-	struct pmu_hw_events *events = this_cpu_ptr(cpu_pmu->hw_events);
-
-	/* Disable counter and interrupt */
-	raw_spin_lock_irqsave(&events->pmu_lock, flags);

 	/* Disable counter */
 	armv7_pmnc_disable_counter(idx);
@@ -1533,23 +1505,17 @@ static void krait_pmu_disable_event(struct perf_event *event)

 	/* Disable interrupt for this counter */
 	armv7_pmnc_disable_intens(idx);
-
-	raw_spin_unlock_irqrestore(&events->pmu_lock, flags);
 }

 static void krait_pmu_enable_event(struct perf_event *event)
 {
-	unsigned long flags;
 	struct hw_perf_event *hwc = &event->hw;
 	int idx = hwc->idx;
-	struct arm_pmu *cpu_pmu = to_arm_pmu(event->pmu);
-	struct pmu_hw_events *events = this_cpu_ptr(cpu_pmu->hw_events);

 	/*
 	 * Enable counter and interrupt, and set the counter to count
 	 * the event that we're interested in.
 	 */
-	raw_spin_lock_irqsave(&events->pmu_lock, flags);

 	/* Disable counter */
 	armv7_pmnc_disable_counter(idx);
@@ -1569,8 +1535,6 @@ static void krait_pmu_enable_event(struct perf_event *event)

 	/* Enable counter */
 	armv7_pmnc_enable_counter(idx);
-
-	raw_spin_unlock_irqrestore(&events->pmu_lock, flags);
 }

 static void krait_pmu_reset(void *info)
@@ -1846,14 +1810,8 @@ static void scorpion_clearpmu(u32 config_base)

 static void scorpion_pmu_disable_event(struct perf_event *event)
 {
-	unsigned long flags;
 	struct hw_perf_event *hwc = &event->hw;
 	int idx = hwc->idx;
-	struct arm_pmu *cpu_pmu = to_arm_pmu(event->pmu);
-	struct pmu_hw_events *events = this_cpu_ptr(cpu_pmu->hw_events);
-
-	/* Disable counter and interrupt */
-	raw_spin_lock_irqsave(&events->pmu_lock, flags);

 	/* Disable counter */
 	armv7_pmnc_disable_counter(idx);
@@ -1866,23 +1824,17 @@ static void scorpion_pmu_disable_event(struct perf_event *event)

 	/* Disable interrupt for this counter */
 	armv7_pmnc_disable_intens(idx);
-
-	raw_spin_unlock_irqrestore(&events->pmu_lock, flags);
 }

 static void scorpion_pmu_enable_event(struct perf_event *event)
 {
-	unsigned long flags;
 	struct hw_perf_event *hwc = &event->hw;
 	int idx = hwc->idx;
-	struct arm_pmu *cpu_pmu = to_arm_pmu(event->pmu);
-	struct pmu_hw_events *events = this_cpu_ptr(cpu_pmu->hw_events);

 	/*
 	 * Enable counter and interrupt, and set the counter to count
 	 * the event that we're interested in.
 	 */
-	raw_spin_lock_irqsave(&events->pmu_lock, flags);

 	/* Disable counter */
 	armv7_pmnc_disable_counter(idx);
@@ -1902,8 +1854,6 @@ static void scorpion_pmu_enable_event(struct perf_event *event)

 	/* Enable counter */
 	armv7_pmnc_enable_counter(idx);
-
-	raw_spin_unlock_irqrestore(&events->pmu_lock, flags);
 }

 static void scorpion_pmu_reset(void *info)
--
1.9.1

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  parent reply index

Thread overview: 24+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-07-17  8:17 [PATCH v4 0/9] arm_pmu: Use NMI for perf interrupt Julien Thierry
2019-07-17  8:17 ` [PATCH v4 1/9] arm64: perf: avoid PMXEV* indirection Julien Thierry
2019-07-17  8:17 ` [PATCH v4 2/9] arm64: perf: Remove PMU locking Julien Thierry
2019-08-01 12:58   ` Will Deacon
2019-08-02 14:26     ` Julien Thierry
2019-07-17  8:17 ` [PATCH v4 3/9] arm: perf: save/resore pmsel Julien Thierry
2019-08-01 13:01   ` Will Deacon
2019-08-02 14:34     ` Julien Thierry
2019-07-17  8:17 ` Julien Thierry [this message]
2019-08-01 13:06   ` [PATCH v4 4/9] arm: perf: Remove Remove PMU locking Will Deacon
2019-08-02 14:36     ` Julien Thierry
2019-07-17  8:17 ` [PATCH v4 5/9] perf/arm_pmu: Move PMU lock to ARMv6 events Julien Thierry
2019-07-17  8:17 ` [PATCH v4 6/9] arm64: perf: Do not call irq_work_run in NMI context Julien Thierry
2019-08-01 13:06   ` Will Deacon
2019-08-02 14:43     ` Julien Thierry
2019-07-17  8:17 ` [PATCH v4 7/9] arm/arm64: kvm: pmu: Make overflow handler NMI safe Julien Thierry
2019-07-17  8:17 ` [PATCH v4 8/9] arm_pmu: Introduce pmu_irq_ops Julien Thierry
2019-07-17  8:17 ` [PATCH v4 9/9] arm_pmu: Use NMIs for PMU Julien Thierry
2019-07-30  9:11   ` Russell King - ARM Linux admin
2019-07-30  9:18     ` Julien Thierry
2019-07-30  9:28       ` Russell King - ARM Linux admin
2019-07-30 14:06         ` Julien Thierry
2019-07-17  9:02 ` [PATCH v4 0/9] arm_pmu: Use NMI for perf interrupt Julien Thierry
2019-07-30  9:05 ` Julien Thierry

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