ARM: 6521/1: perf: use raw_spinlock_t for pmu_lock

For kernels built with PREEMPT_RT, critical sections protected
by standard spinlocks are preemptible. This is not acceptable
on perf as (a) we may be scheduled onto a different CPU whilst
reading/writing banked PMU registers and (b) the latency when
reading the PMU registers becomes unpredictable.

This patch upgrades the pmu_lock spinlock to a raw_spinlock
instead.

Reported-by: Jamie Iles <jamie@jamieiles.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

4 files changed, 35 insertions, 35 deletions

diff --git a/arch/arm/kernel/perf_event.c b/arch/arm/kernel/perf_event.c
index 50c197bfac0f..624e2a5de2b3 100644
--- a/arch/arm/kernel/perf_event.c
+++ b/arch/arm/kernel/perf_event.c
@@ -32,7 +32,7 @@ static struct platform_device *pmu_device;
  * Hardware lock to serialize accesses to PMU registers. Needed for the
  * read/modify/write sequences.
  */
-static DEFINE_SPINLOCK(pmu_lock);
+static DEFINE_RAW_SPINLOCK(pmu_lock);
 
 /*
  * ARMv6 supports a maximum of 3 events, starting from index 1. If we add
diff --git a/arch/arm/kernel/perf_event_v6.c b/arch/arm/kernel/perf_event_v6.c
index 3f427aae211d..c058bfc8532b 100644
--- a/arch/arm/kernel/perf_event_v6.c
+++ b/arch/arm/kernel/perf_event_v6.c
@@ -426,12 +426,12 @@ 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.
          */
-        spin_lock_irqsave(&pmu_lock, flags);
+        raw_spin_lock_irqsave(&pmu_lock, flags);
         val = armv6_pmcr_read();
         val &= ~mask;
         val |= evt;
         armv6_pmcr_write(val);
-        spin_unlock_irqrestore(&pmu_lock, flags);
+        raw_spin_unlock_irqrestore(&pmu_lock, flags);
 }
 
 static irqreturn_t
@@ -500,11 +500,11 @@ armv6pmu_start(void)
 {
         unsigned long flags, val;
 
-        spin_lock_irqsave(&pmu_lock, flags);
+        raw_spin_lock_irqsave(&pmu_lock, flags);
         val = armv6_pmcr_read();
         val |= ARMV6_PMCR_ENABLE;
         armv6_pmcr_write(val);
-        spin_unlock_irqrestore(&pmu_lock, flags);
+        raw_spin_unlock_irqrestore(&pmu_lock, flags);
 }
 
 static void
@@ -512,11 +512,11 @@ armv6pmu_stop(void)
 {
         unsigned long flags, val;
 
-        spin_lock_irqsave(&pmu_lock, flags);
+        raw_spin_lock_irqsave(&pmu_lock, flags);
         val = armv6_pmcr_read();
         val &= ~ARMV6_PMCR_ENABLE;
         armv6_pmcr_write(val);
-        spin_unlock_irqrestore(&pmu_lock, flags);
+        raw_spin_unlock_irqrestore(&pmu_lock, flags);
 }
 
 static int
@@ -570,12 +570,12 @@ 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.
          */
-        spin_lock_irqsave(&pmu_lock, flags);
+        raw_spin_lock_irqsave(&pmu_lock, flags);
         val = armv6_pmcr_read();
         val &= ~mask;
         val |= evt;
         armv6_pmcr_write(val);
-        spin_unlock_irqrestore(&pmu_lock, flags);
+        raw_spin_unlock_irqrestore(&pmu_lock, flags);
 }
 
 static void
@@ -599,12 +599,12 @@ 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.
          */
-        spin_lock_irqsave(&pmu_lock, flags);
+        raw_spin_lock_irqsave(&pmu_lock, flags);
         val = armv6_pmcr_read();
         val &= ~mask;
         val |= evt;
         armv6_pmcr_write(val);
-        spin_unlock_irqrestore(&pmu_lock, flags);
+        raw_spin_unlock_irqrestore(&pmu_lock, flags);
 }
 
 static const struct arm_pmu armv6pmu = {
diff --git a/arch/arm/kernel/perf_event_v7.c b/arch/arm/kernel/perf_event_v7.c
index a68ff1c10dec..2e1402556fa0 100644
--- a/arch/arm/kernel/perf_event_v7.c
+++ b/arch/arm/kernel/perf_event_v7.c
@@ -689,7 +689,7 @@ static void armv7pmu_enable_event(struct hw_perf_event *hwc, int idx)
          * Enable counter and interrupt, and set the counter to count
          * the event that we're interested in.
          */
-        spin_lock_irqsave(&pmu_lock, flags);
+        raw_spin_lock_irqsave(&pmu_lock, flags);
 
         /*
          * Disable counter
@@ -713,7 +713,7 @@ static void armv7pmu_enable_event(struct hw_perf_event *hwc, int idx)
          */
         armv7_pmnc_enable_counter(idx);
 
-        spin_unlock_irqrestore(&pmu_lock, flags);
+        raw_spin_unlock_irqrestore(&pmu_lock, flags);
 }
 
 static void armv7pmu_disable_event(struct hw_perf_event *hwc, int idx)
@@ -723,7 +723,7 @@ static void armv7pmu_disable_event(struct hw_perf_event *hwc, int idx)
         /*
          * Disable counter and interrupt
          */
-        spin_lock_irqsave(&pmu_lock, flags);
+        raw_spin_lock_irqsave(&pmu_lock, flags);
 
         /*
          * Disable counter
@@ -735,7 +735,7 @@ static void armv7pmu_disable_event(struct hw_perf_event *hwc, int idx)
          */
         armv7_pmnc_disable_intens(idx);
 
-        spin_unlock_irqrestore(&pmu_lock, flags);
+        raw_spin_unlock_irqrestore(&pmu_lock, flags);
 }
 
 static irqreturn_t armv7pmu_handle_irq(int irq_num, void *dev)
@@ -805,20 +805,20 @@ static void armv7pmu_start(void)
 {
         unsigned long flags;
 
-        spin_lock_irqsave(&pmu_lock, flags);
+        raw_spin_lock_irqsave(&pmu_lock, flags);
         /* Enable all counters */
         armv7_pmnc_write(armv7_pmnc_read() | ARMV7_PMNC_E);
-        spin_unlock_irqrestore(&pmu_lock, flags);
+        raw_spin_unlock_irqrestore(&pmu_lock, flags);
 }
 
 static void armv7pmu_stop(void)
 {
         unsigned long flags;
 
-        spin_lock_irqsave(&pmu_lock, flags);
+        raw_spin_lock_irqsave(&pmu_lock, flags);
         /* Disable all counters */
         armv7_pmnc_write(armv7_pmnc_read() & ~ARMV7_PMNC_E);
-        spin_unlock_irqrestore(&pmu_lock, flags);
+        raw_spin_unlock_irqrestore(&pmu_lock, flags);
 }
 
 static int armv7pmu_get_event_idx(struct cpu_hw_events *cpuc,
diff --git a/arch/arm/kernel/perf_event_xscale.c b/arch/arm/kernel/perf_event_xscale.c
index f14fbb6c345b..28cd3b025bc3 100644
--- a/arch/arm/kernel/perf_event_xscale.c
+++ b/arch/arm/kernel/perf_event_xscale.c
@@ -291,12 +291,12 @@ xscale1pmu_enable_event(struct hw_perf_event *hwc, int idx)
                 return;
         }
 
-        spin_lock_irqsave(&pmu_lock, flags);
+        raw_spin_lock_irqsave(&pmu_lock, flags);
         val = xscale1pmu_read_pmnc();
         val &= ~mask;
         val |= evt;
         xscale1pmu_write_pmnc(val);
-        spin_unlock_irqrestore(&pmu_lock, flags);
+        raw_spin_unlock_irqrestore(&pmu_lock, flags);
 }
 
 static void
@@ -322,12 +322,12 @@ xscale1pmu_disable_event(struct hw_perf_event *hwc, int idx)
                 return;
         }
 
-        spin_lock_irqsave(&pmu_lock, flags);
+        raw_spin_lock_irqsave(&pmu_lock, flags);
         val = xscale1pmu_read_pmnc();
         val &= ~mask;
         val |= evt;
         xscale1pmu_write_pmnc(val);
-        spin_unlock_irqrestore(&pmu_lock, flags);
+        raw_spin_unlock_irqrestore(&pmu_lock, flags);
 }
 
 static int
@@ -355,11 +355,11 @@ xscale1pmu_start(void)
 {
         unsigned long flags, val;
 
-        spin_lock_irqsave(&pmu_lock, flags);
+        raw_spin_lock_irqsave(&pmu_lock, flags);
         val = xscale1pmu_read_pmnc();
         val |= XSCALE_PMU_ENABLE;
         xscale1pmu_write_pmnc(val);
-        spin_unlock_irqrestore(&pmu_lock, flags);
+        raw_spin_unlock_irqrestore(&pmu_lock, flags);
 }
 
 static void
@@ -367,11 +367,11 @@ xscale1pmu_stop(void)
 {
         unsigned long flags, val;
 
-        spin_lock_irqsave(&pmu_lock, flags);
+        raw_spin_lock_irqsave(&pmu_lock, flags);
         val = xscale1pmu_read_pmnc();
         val &= ~XSCALE_PMU_ENABLE;
         xscale1pmu_write_pmnc(val);
-        spin_unlock_irqrestore(&pmu_lock, flags);
+        raw_spin_unlock_irqrestore(&pmu_lock, flags);
 }
 
 static inline u32
@@ -635,10 +635,10 @@ xscale2pmu_enable_event(struct hw_perf_event *hwc, int idx)
                 return;
         }
 
-        spin_lock_irqsave(&pmu_lock, flags);
+        raw_spin_lock_irqsave(&pmu_lock, flags);
         xscale2pmu_write_event_select(evtsel);
         xscale2pmu_write_int_enable(ien);
-        spin_unlock_irqrestore(&pmu_lock, flags);
+        raw_spin_unlock_irqrestore(&pmu_lock, flags);
 }
 
 static void
@@ -678,10 +678,10 @@ xscale2pmu_disable_event(struct hw_perf_event *hwc, int idx)
                 return;
         }
 
-        spin_lock_irqsave(&pmu_lock, flags);
+        raw_spin_lock_irqsave(&pmu_lock, flags);
         xscale2pmu_write_event_select(evtsel);
         xscale2pmu_write_int_enable(ien);
-        spin_unlock_irqrestore(&pmu_lock, flags);
+        raw_spin_unlock_irqrestore(&pmu_lock, flags);
 }
 
 static int
@@ -705,11 +705,11 @@ xscale2pmu_start(void)
 {
         unsigned long flags, val;
 
-        spin_lock_irqsave(&pmu_lock, flags);
+        raw_spin_lock_irqsave(&pmu_lock, flags);
         val = xscale2pmu_read_pmnc() & ~XSCALE_PMU_CNT64;
         val |= XSCALE_PMU_ENABLE;
         xscale2pmu_write_pmnc(val);
-        spin_unlock_irqrestore(&pmu_lock, flags);
+        raw_spin_unlock_irqrestore(&pmu_lock, flags);
 }
 
 static void
@@ -717,11 +717,11 @@ xscale2pmu_stop(void)
 {
         unsigned long flags, val;
 
-        spin_lock_irqsave(&pmu_lock, flags);
+        raw_spin_lock_irqsave(&pmu_lock, flags);
         val = xscale2pmu_read_pmnc();
         val &= ~XSCALE_PMU_ENABLE;
         xscale2pmu_write_pmnc(val);
-        spin_unlock_irqrestore(&pmu_lock, flags);
+        raw_spin_unlock_irqrestore(&pmu_lock, flags);
 }
 
 static inline u32