From 89cbc76768c2fa4ed95545bf961f3a14ddfeed21 Mon Sep 17 00:00:00 2001 From: Christoph Lameter Date: Sun, 17 Aug 2014 12:30:40 -0500 Subject: x86: Replace __get_cpu_var uses __get_cpu_var() is used for multiple purposes in the kernel source. One of them is address calculation via the form &__get_cpu_var(x). This calculates the address for the instance of the percpu variable of the current processor based on an offset. Other use cases are for storing and retrieving data from the current processors percpu area. __get_cpu_var() can be used as an lvalue when writing data or on the right side of an assignment. __get_cpu_var() is defined as : #define __get_cpu_var(var) (*this_cpu_ptr(&(var))) __get_cpu_var() always only does an address determination. However, store and retrieve operations could use a segment prefix (or global register on other platforms) to avoid the address calculation. this_cpu_write() and this_cpu_read() can directly take an offset into a percpu area and use optimized assembly code to read and write per cpu variables. This patch converts __get_cpu_var into either an explicit address calculation using this_cpu_ptr() or into a use of this_cpu operations that use the offset. Thereby address calculations are avoided and less registers are used when code is generated. Transformations done to __get_cpu_var() 1. Determine the address of the percpu instance of the current processor. DEFINE_PER_CPU(int, y); int *x = &__get_cpu_var(y); Converts to int *x = this_cpu_ptr(&y); 2. Same as #1 but this time an array structure is involved. DEFINE_PER_CPU(int, y[20]); int *x = __get_cpu_var(y); Converts to int *x = this_cpu_ptr(y); 3. Retrieve the content of the current processors instance of a per cpu variable. DEFINE_PER_CPU(int, y); int x = __get_cpu_var(y) Converts to int x = __this_cpu_read(y); 4. Retrieve the content of a percpu struct DEFINE_PER_CPU(struct mystruct, y); struct mystruct x = __get_cpu_var(y); Converts to memcpy(&x, this_cpu_ptr(&y), sizeof(x)); 5. Assignment to a per cpu variable DEFINE_PER_CPU(int, y) __get_cpu_var(y) = x; Converts to __this_cpu_write(y, x); 6. Increment/Decrement etc of a per cpu variable DEFINE_PER_CPU(int, y); __get_cpu_var(y)++ Converts to __this_cpu_inc(y) Cc: Thomas Gleixner Cc: x86@kernel.org Acked-by: H. Peter Anvin Acked-by: Ingo Molnar Signed-off-by: Christoph Lameter Signed-off-by: Tejun Heo --- arch/x86/oprofile/nmi_int.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) (limited to 'arch/x86/oprofile') diff --git a/arch/x86/oprofile/nmi_int.c b/arch/x86/oprofile/nmi_int.c index 379e8bd0deea..1d2e6392f5fa 100644 --- a/arch/x86/oprofile/nmi_int.c +++ b/arch/x86/oprofile/nmi_int.c @@ -64,11 +64,11 @@ u64 op_x86_get_ctrl(struct op_x86_model_spec const *model, static int profile_exceptions_notify(unsigned int val, struct pt_regs *regs) { if (ctr_running) - model->check_ctrs(regs, &__get_cpu_var(cpu_msrs)); + model->check_ctrs(regs, this_cpu_ptr(&cpu_msrs)); else if (!nmi_enabled) return NMI_DONE; else - model->stop(&__get_cpu_var(cpu_msrs)); + model->stop(this_cpu_ptr(&cpu_msrs)); return NMI_HANDLED; } @@ -91,7 +91,7 @@ static void nmi_cpu_save_registers(struct op_msrs *msrs) static void nmi_cpu_start(void *dummy) { - struct op_msrs const *msrs = &__get_cpu_var(cpu_msrs); + struct op_msrs const *msrs = this_cpu_ptr(&cpu_msrs); if (!msrs->controls) WARN_ON_ONCE(1); else @@ -111,7 +111,7 @@ static int nmi_start(void) static void nmi_cpu_stop(void *dummy) { - struct op_msrs const *msrs = &__get_cpu_var(cpu_msrs); + struct op_msrs const *msrs = this_cpu_ptr(&cpu_msrs); if (!msrs->controls) WARN_ON_ONCE(1); else -- cgit v1.2.3