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ARM: perf: lock PMU registers per-CPU
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Currently, a single lock serialises access to CPU PMU registers. This
global locking is unnecessary as PMU registers are local to the CPU
they monitor.

This patch replaces the global lock with a per-CPU lock. As the lock is
in struct cpu_hw_events, PMUs providing a single cpu_hw_events instance
can be locked globally.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Reviewed-by: Will Deacon <will.deacon@arm.com>
Reviewed-by: Jamie Iles <jamie@jamieiles.com>
Reviewed-by: Ashwin Chaugule <ashwinc@codeaurora.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>
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Mark Rutland authored and Will Deacon committed Aug 31, 2011
1 parent 1b69beb commit 0f78d2d
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Showing 4 changed files with 62 additions and 40 deletions.
17 changes: 11 additions & 6 deletions arch/arm/kernel/perf_event.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -26,12 +26,6 @@
#include <asm/pmu.h>
#include <asm/stacktrace.h>

/*
* Hardware lock to serialize accesses to PMU registers. Needed for the
* read/modify/write sequences.
*/
static DEFINE_RAW_SPINLOCK(pmu_lock);

/*
* ARMv6 supports a maximum of 3 events, starting from index 0. If we add
* another platform that supports more, we need to increase this to be the
Expand All @@ -55,6 +49,12 @@ struct cpu_hw_events {
* an event. A 0 means that the counter can be used.
*/
unsigned long used_mask[BITS_TO_LONGS(ARMPMU_MAX_HWEVENTS)];

/*
* Hardware lock to serialize accesses to PMU registers. Needed for the
* read/modify/write sequences.
*/
raw_spinlock_t pmu_lock;
};
static DEFINE_PER_CPU(struct cpu_hw_events, cpu_hw_events);

Expand Down Expand Up @@ -685,6 +685,11 @@ static struct cpu_hw_events *armpmu_get_cpu_events(void)

static void __init cpu_pmu_init(struct arm_pmu *armpmu)
{
int cpu;
for_each_possible_cpu(cpu) {
struct cpu_hw_events *events = &per_cpu(cpu_hw_events, cpu);
raw_spin_lock_init(&events->pmu_lock);
}
armpmu->get_hw_events = armpmu_get_cpu_events;
}

Expand Down
25 changes: 15 additions & 10 deletions arch/arm/kernel/perf_event_v6.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -433,6 +433,7 @@ armv6pmu_enable_event(struct hw_perf_event *hwc,
int idx)
{
unsigned long val, mask, evt, flags;
struct cpu_hw_events *events = armpmu->get_hw_events();

if (ARMV6_CYCLE_COUNTER == idx) {
mask = 0;
Expand All @@ -454,12 +455,12 @@ armv6pmu_enable_event(struct hw_perf_event *hwc,
* Mask out the current event and set the counter to count the event
* that we're interested in.
*/
raw_spin_lock_irqsave(&pmu_lock, flags);
raw_spin_lock_irqsave(&events->pmu_lock, flags);
val = armv6_pmcr_read();
val &= ~mask;
val |= evt;
armv6_pmcr_write(val);
raw_spin_unlock_irqrestore(&pmu_lock, flags);
raw_spin_unlock_irqrestore(&events->pmu_lock, flags);
}

static int counter_is_active(unsigned long pmcr, int idx)
Expand Down Expand Up @@ -544,24 +545,26 @@ static void
armv6pmu_start(void)
{
unsigned long flags, val;
struct cpu_hw_events *events = armpmu->get_hw_events();

raw_spin_lock_irqsave(&pmu_lock, flags);
raw_spin_lock_irqsave(&events->pmu_lock, flags);
val = armv6_pmcr_read();
val |= ARMV6_PMCR_ENABLE;
armv6_pmcr_write(val);
raw_spin_unlock_irqrestore(&pmu_lock, flags);
raw_spin_unlock_irqrestore(&events->pmu_lock, flags);
}

static void
armv6pmu_stop(void)
{
unsigned long flags, val;
struct cpu_hw_events *events = armpmu->get_hw_events();

raw_spin_lock_irqsave(&pmu_lock, flags);
raw_spin_lock_irqsave(&events->pmu_lock, flags);
val = armv6_pmcr_read();
val &= ~ARMV6_PMCR_ENABLE;
armv6_pmcr_write(val);
raw_spin_unlock_irqrestore(&pmu_lock, flags);
raw_spin_unlock_irqrestore(&events->pmu_lock, flags);
}

static int
Expand Down Expand Up @@ -595,6 +598,7 @@ armv6pmu_disable_event(struct hw_perf_event *hwc,
int idx)
{
unsigned long val, mask, evt, flags;
struct cpu_hw_events *events = armpmu->get_hw_events();

if (ARMV6_CYCLE_COUNTER == idx) {
mask = ARMV6_PMCR_CCOUNT_IEN;
Expand All @@ -615,19 +619,20 @@ armv6pmu_disable_event(struct hw_perf_event *hwc,
* of ETM bus signal assertion cycles. The external reporting should
* be disabled and so this should never increment.
*/
raw_spin_lock_irqsave(&pmu_lock, flags);
raw_spin_lock_irqsave(&events->pmu_lock, flags);
val = armv6_pmcr_read();
val &= ~mask;
val |= evt;
armv6_pmcr_write(val);
raw_spin_unlock_irqrestore(&pmu_lock, flags);
raw_spin_unlock_irqrestore(&events->pmu_lock, flags);
}

static void
armv6mpcore_pmu_disable_event(struct hw_perf_event *hwc,
int idx)
{
unsigned long val, mask, flags, evt = 0;
struct cpu_hw_events *events = armpmu->get_hw_events();

if (ARMV6_CYCLE_COUNTER == idx) {
mask = ARMV6_PMCR_CCOUNT_IEN;
Expand All @@ -644,12 +649,12 @@ armv6mpcore_pmu_disable_event(struct hw_perf_event *hwc,
* Unlike UP ARMv6, we don't have a way of stopping the counters. We
* simply disable the interrupt reporting.
*/
raw_spin_lock_irqsave(&pmu_lock, flags);
raw_spin_lock_irqsave(&events->pmu_lock, flags);
val = armv6_pmcr_read();
val &= ~mask;
val |= evt;
armv6_pmcr_write(val);
raw_spin_unlock_irqrestore(&pmu_lock, flags);
raw_spin_unlock_irqrestore(&events->pmu_lock, flags);
}

static struct arm_pmu armv6pmu = {
Expand Down
20 changes: 12 additions & 8 deletions arch/arm/kernel/perf_event_v7.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -936,12 +936,13 @@ static void armv7_pmnc_dump_regs(void)
static void armv7pmu_enable_event(struct hw_perf_event *hwc, int idx)
{
unsigned long flags;
struct cpu_hw_events *events = armpmu->get_hw_events();

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

/*
* Disable counter
Expand All @@ -966,17 +967,18 @@ static void armv7pmu_enable_event(struct hw_perf_event *hwc, int idx)
*/
armv7_pmnc_enable_counter(idx);

raw_spin_unlock_irqrestore(&pmu_lock, flags);
raw_spin_unlock_irqrestore(&events->pmu_lock, flags);
}

static void armv7pmu_disable_event(struct hw_perf_event *hwc, int idx)
{
unsigned long flags;
struct cpu_hw_events *events = armpmu->get_hw_events();

/*
* Disable counter and interrupt
*/
raw_spin_lock_irqsave(&pmu_lock, flags);
raw_spin_lock_irqsave(&events->pmu_lock, flags);

/*
* Disable counter
Expand All @@ -988,7 +990,7 @@ static void armv7pmu_disable_event(struct hw_perf_event *hwc, int idx)
*/
armv7_pmnc_disable_intens(idx);

raw_spin_unlock_irqrestore(&pmu_lock, flags);
raw_spin_unlock_irqrestore(&events->pmu_lock, flags);
}

static irqreturn_t armv7pmu_handle_irq(int irq_num, void *dev)
Expand Down Expand Up @@ -1054,21 +1056,23 @@ static irqreturn_t armv7pmu_handle_irq(int irq_num, void *dev)
static void armv7pmu_start(void)
{
unsigned long flags;
struct cpu_hw_events *events = armpmu->get_hw_events();

raw_spin_lock_irqsave(&pmu_lock, flags);
raw_spin_lock_irqsave(&events->pmu_lock, flags);
/* Enable all counters */
armv7_pmnc_write(armv7_pmnc_read() | ARMV7_PMNC_E);
raw_spin_unlock_irqrestore(&pmu_lock, flags);
raw_spin_unlock_irqrestore(&events->pmu_lock, flags);
}

static void armv7pmu_stop(void)
{
unsigned long flags;
struct cpu_hw_events *events = armpmu->get_hw_events();

raw_spin_lock_irqsave(&pmu_lock, flags);
raw_spin_lock_irqsave(&events->pmu_lock, flags);
/* Disable all counters */
armv7_pmnc_write(armv7_pmnc_read() & ~ARMV7_PMNC_E);
raw_spin_unlock_irqrestore(&pmu_lock, flags);
raw_spin_unlock_irqrestore(&events->pmu_lock, flags);
}

static int armv7pmu_get_event_idx(struct cpu_hw_events *cpuc,
Expand Down
40 changes: 24 additions & 16 deletions arch/arm/kernel/perf_event_xscale.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -281,6 +281,7 @@ static void
xscale1pmu_enable_event(struct hw_perf_event *hwc, int idx)
{
unsigned long val, mask, evt, flags;
struct cpu_hw_events *events = armpmu->get_hw_events();

switch (idx) {
case XSCALE_CYCLE_COUNTER:
Expand All @@ -302,18 +303,19 @@ xscale1pmu_enable_event(struct hw_perf_event *hwc, int idx)
return;
}

raw_spin_lock_irqsave(&pmu_lock, flags);
raw_spin_lock_irqsave(&events->pmu_lock, flags);
val = xscale1pmu_read_pmnc();
val &= ~mask;
val |= evt;
xscale1pmu_write_pmnc(val);
raw_spin_unlock_irqrestore(&pmu_lock, flags);
raw_spin_unlock_irqrestore(&events->pmu_lock, flags);
}

static void
xscale1pmu_disable_event(struct hw_perf_event *hwc, int idx)
{
unsigned long val, mask, evt, flags;
struct cpu_hw_events *events = armpmu->get_hw_events();

switch (idx) {
case XSCALE_CYCLE_COUNTER:
Expand All @@ -333,12 +335,12 @@ xscale1pmu_disable_event(struct hw_perf_event *hwc, int idx)
return;
}

raw_spin_lock_irqsave(&pmu_lock, flags);
raw_spin_lock_irqsave(&events->pmu_lock, flags);
val = xscale1pmu_read_pmnc();
val &= ~mask;
val |= evt;
xscale1pmu_write_pmnc(val);
raw_spin_unlock_irqrestore(&pmu_lock, flags);
raw_spin_unlock_irqrestore(&events->pmu_lock, flags);
}

static int
Expand All @@ -365,24 +367,26 @@ static void
xscale1pmu_start(void)
{
unsigned long flags, val;
struct cpu_hw_events *events = armpmu->get_hw_events();

raw_spin_lock_irqsave(&pmu_lock, flags);
raw_spin_lock_irqsave(&events->pmu_lock, flags);
val = xscale1pmu_read_pmnc();
val |= XSCALE_PMU_ENABLE;
xscale1pmu_write_pmnc(val);
raw_spin_unlock_irqrestore(&pmu_lock, flags);
raw_spin_unlock_irqrestore(&events->pmu_lock, flags);
}

static void
xscale1pmu_stop(void)
{
unsigned long flags, val;
struct cpu_hw_events *events = armpmu->get_hw_events();

raw_spin_lock_irqsave(&pmu_lock, flags);
raw_spin_lock_irqsave(&events->pmu_lock, flags);
val = xscale1pmu_read_pmnc();
val &= ~XSCALE_PMU_ENABLE;
xscale1pmu_write_pmnc(val);
raw_spin_unlock_irqrestore(&pmu_lock, flags);
raw_spin_unlock_irqrestore(&events->pmu_lock, flags);
}

static inline u32
Expand Down Expand Up @@ -610,6 +614,7 @@ static void
xscale2pmu_enable_event(struct hw_perf_event *hwc, int idx)
{
unsigned long flags, ien, evtsel;
struct cpu_hw_events *events = armpmu->get_hw_events();

ien = xscale2pmu_read_int_enable();
evtsel = xscale2pmu_read_event_select();
Expand Down Expand Up @@ -643,16 +648,17 @@ xscale2pmu_enable_event(struct hw_perf_event *hwc, int idx)
return;
}

raw_spin_lock_irqsave(&pmu_lock, flags);
raw_spin_lock_irqsave(&events->pmu_lock, flags);
xscale2pmu_write_event_select(evtsel);
xscale2pmu_write_int_enable(ien);
raw_spin_unlock_irqrestore(&pmu_lock, flags);
raw_spin_unlock_irqrestore(&events->pmu_lock, flags);
}

static void
xscale2pmu_disable_event(struct hw_perf_event *hwc, int idx)
{
unsigned long flags, ien, evtsel;
struct cpu_hw_events *events = armpmu->get_hw_events();

ien = xscale2pmu_read_int_enable();
evtsel = xscale2pmu_read_event_select();
Expand Down Expand Up @@ -686,10 +692,10 @@ xscale2pmu_disable_event(struct hw_perf_event *hwc, int idx)
return;
}

raw_spin_lock_irqsave(&pmu_lock, flags);
raw_spin_lock_irqsave(&events->pmu_lock, flags);
xscale2pmu_write_event_select(evtsel);
xscale2pmu_write_int_enable(ien);
raw_spin_unlock_irqrestore(&pmu_lock, flags);
raw_spin_unlock_irqrestore(&events->pmu_lock, flags);
}

static int
Expand All @@ -712,24 +718,26 @@ static void
xscale2pmu_start(void)
{
unsigned long flags, val;
struct cpu_hw_events *events = armpmu->get_hw_events();

raw_spin_lock_irqsave(&pmu_lock, flags);
raw_spin_lock_irqsave(&events->pmu_lock, flags);
val = xscale2pmu_read_pmnc() & ~XSCALE_PMU_CNT64;
val |= XSCALE_PMU_ENABLE;
xscale2pmu_write_pmnc(val);
raw_spin_unlock_irqrestore(&pmu_lock, flags);
raw_spin_unlock_irqrestore(&events->pmu_lock, flags);
}

static void
xscale2pmu_stop(void)
{
unsigned long flags, val;
struct cpu_hw_events *events = armpmu->get_hw_events();

raw_spin_lock_irqsave(&pmu_lock, flags);
raw_spin_lock_irqsave(&events->pmu_lock, flags);
val = xscale2pmu_read_pmnc();
val &= ~XSCALE_PMU_ENABLE;
xscale2pmu_write_pmnc(val);
raw_spin_unlock_irqrestore(&pmu_lock, flags);
raw_spin_unlock_irqrestore(&events->pmu_lock, flags);
}

static inline u32
Expand Down

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