[RFC PATCH v2 09/12] x86/apic: Use non-atomic operations when possible

Nadav Amit
2019-05-31T06:37:25Z

Using __clear_bit() and __cpumask_clear_cpu() is more efficient than
using their atomic counterparts. Use them when atomicity is not needed,
such as when manipulating bitmasks that are on the stack.

Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Nadav Amit <namit@vmware.com>
---
arch/x86/kernel/apic/apic_flat_64.c | 4 ++--
arch/x86/kernel/apic/x2apic_cluster.c | 2 +-
arch/x86/kernel/smp.c | 2 +-
3 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/arch/x86/kernel/apic/apic_flat_64.c b/arch/x86/kernel/apic/apic_flat_64.c
index 0005c284a5c5..65072858f553 100644
--- a/arch/x86/kernel/apic/apic_flat_64.c
+++ b/arch/x86/kernel/apic/apic_flat_64.c
@@ -78,7 +78,7 @@ flat_send_IPI_mask_allbutself(const struct cpumask *cpumask, int vector)
int cpu = smp_processor_id();

if (cpu < BITS_PER_LONG)
- clear_bit(cpu, &mask);
+ __clear_bit(cpu, &mask);

_flat_send_IPI_mask(mask, vector);
}
@@ -92,7 +92,7 @@ static void flat_send_IPI_allbutself(int vector)
unsigned long mask = cpumask_bits(cpu_online_mask)[0];

if (cpu < BITS_PER_LONG)
- clear_bit(cpu, &mask);
+ __clear_bit(cpu, &mask);

_flat_send_IPI_mask(mask, vector);
}
diff --git a/arch/x86/kernel/apic/x2apic_cluster.c b/arch/x86/kernel/apic/x2apic_cluster.c
index 7685444a106b..609e499387a1 100644
--- a/arch/x86/kernel/apic/x2apic_cluster.c
+++ b/arch/x86/kernel/apic/x2apic_cluster.c
@@ -50,7 +50,7 @@ __x2apic_send_IPI_mask(const struct cpumask *mask, int vector, int apic_dest)
cpumask_copy(tmpmsk, mask);
/* If IPI should not be sent to self, clear current CPU */
if (apic_dest != APIC_DEST_ALLINC)
- cpumask_clear_cpu(smp_processor_id(), tmpmsk);
+ __cpumask_clear_cpu(smp_processor_id(), tmpmsk);

/* Collapse cpus in a cluster so a single IPI per cluster is sent */
for_each_cpu(cpu, tmpmsk) {
diff --git a/arch/x86/kernel/smp.c b/arch/x86/kernel/smp.c
index 04adc8d60aed..acddd988602d 100644
--- a/arch/x86/kernel/smp.c
+++ b/arch/x86/kernel/smp.c
@@ -146,7 +146,7 @@ void native_send_call_func_ipi(const struct cpumask *mask)
}

cpumask_copy(allbutself, cpu_online_mask);
- cpumask_clear_cpu(smp_processor_id(), allbutself);
+ __cpumask_clear_cpu(smp_processor_id(), allbutself);

if (cpumask_equal(mask, allbutself) &&
cpumask_equal(cpu_online_mask, cpu_callout_mask))
--
2.20.1