percpu: add optimized generic percpu accessors

It is an optimization and a cleanup, and adds the following new
generic percpu methods:

  percpu_read()
  percpu_write()
  percpu_add()
  percpu_sub()
  percpu_and()
  percpu_or()
  percpu_xor()

and implements support for them on x86. (other architectures will fall
back to a default implementation)

The advantage is that for example to read a local percpu variable,
instead of this sequence:

 return __get_cpu_var(var);

 ffffffff8102ca2b:	48 8b 14 fd 80 09 74 	mov    -0x7e8bf680(,%rdi,8),%rdx
 ffffffff8102ca32:	81
 ffffffff8102ca33:	48 c7 c0 d8 59 00 00 	mov    $0x59d8,%rax
 ffffffff8102ca3a:	48 8b 04 10          	mov    (%rax,%rdx,1),%rax

We can get a single instruction by using the optimized variants:

 return percpu_read(var);

 ffffffff8102ca3f:	65 48 8b 05 91 8f fd 	mov    %gs:0x7efd8f91(%rip),%rax

I also cleaned up the x86-specific APIs and made the x86 code use
these new generic percpu primitives.

tj: * fixed generic percpu_sub() definition as Roel Kluin pointed out
    * added percpu_and() for completeness's sake
    * made generic percpu ops atomic against preemption

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Tejun Heo <tj@kernel.org>

15 files changed, 102 insertions, 48 deletions

diff --git a/arch/x86/include/asm/current.h b/arch/x86/include/asm/current.h
index 0930b4f8d672..0728480f5c56 100644
--- a/arch/x86/include/asm/current.h
+++ b/arch/x86/include/asm/current.h
@@ -10,7 +10,7 @@ struct task_struct;
 DECLARE_PER_CPU(struct task_struct *, current_task);
 static __always_inline struct task_struct *get_current(void)
 {
-        return x86_read_percpu(current_task);
+        return percpu_read(current_task);
 }
 
 #else /* X86_32 */
diff --git a/arch/x86/include/asm/irq_regs_32.h b/arch/x86/include/asm/irq_regs_32.h
index 86afd7473457..d7ed33ee94e9 100644
--- a/arch/x86/include/asm/irq_regs_32.h
+++ b/arch/x86/include/asm/irq_regs_32.h
@@ -15,7 +15,7 @@ DECLARE_PER_CPU(struct pt_regs *, irq_regs);
 
 static inline struct pt_regs *get_irq_regs(void)
 {
-        return x86_read_percpu(irq_regs);
+        return percpu_read(irq_regs);
 }
 
 static inline struct pt_regs *set_irq_regs(struct pt_regs *new_regs)
@@ -23,7 +23,7 @@ static inline struct pt_regs *set_irq_regs(struct pt_regs *new_regs)
         struct pt_regs *old_regs;
 
         old_regs = get_irq_regs();
-        x86_write_percpu(irq_regs, new_regs);
+        percpu_write(irq_regs, new_regs);
 
         return old_regs;
 }
diff --git a/arch/x86/include/asm/mmu_context_32.h b/arch/x86/include/asm/mmu_context_32.h
index 7e98ce1d2c0e..08b53454f831 100644
--- a/arch/x86/include/asm/mmu_context_32.h
+++ b/arch/x86/include/asm/mmu_context_32.h
@@ -4,8 +4,8 @@
 static inline void enter_lazy_tlb(struct mm_struct *mm, struct task_struct *tsk)
 {
 #ifdef CONFIG_SMP
-        if (x86_read_percpu(cpu_tlbstate.state) == TLBSTATE_OK)
-                x86_write_percpu(cpu_tlbstate.state, TLBSTATE_LAZY);
+        if (percpu_read(cpu_tlbstate.state) == TLBSTATE_OK)
+                percpu_write(cpu_tlbstate.state, TLBSTATE_LAZY);
 #endif
 }
 
@@ -19,8 +19,8 @@ static inline void switch_mm(struct mm_struct *prev,
                 /* stop flush ipis for the previous mm */
                 cpu_clear(cpu, prev->cpu_vm_mask);
 #ifdef CONFIG_SMP
-                x86_write_percpu(cpu_tlbstate.state, TLBSTATE_OK);
-                x86_write_percpu(cpu_tlbstate.active_mm, next);
+                percpu_write(cpu_tlbstate.state, TLBSTATE_OK);
+                percpu_write(cpu_tlbstate.active_mm, next);
 #endif
                 cpu_set(cpu, next->cpu_vm_mask);
 
@@ -35,8 +35,8 @@ static inline void switch_mm(struct mm_struct *prev,
         }
 #ifdef CONFIG_SMP
         else {
-                x86_write_percpu(cpu_tlbstate.state, TLBSTATE_OK);
-                BUG_ON(x86_read_percpu(cpu_tlbstate.active_mm) != next);
+                percpu_write(cpu_tlbstate.state, TLBSTATE_OK);
+                BUG_ON(percpu_read(cpu_tlbstate.active_mm) != next);
 
                 if (!cpu_test_and_set(cpu, next->cpu_vm_mask)) {
                         /* We were in lazy tlb mode and leave_mm disabled
diff --git a/arch/x86/include/asm/pda.h b/arch/x86/include/asm/pda.h
index e3d3a081d798..47f274fe6953 100644
--- a/arch/x86/include/asm/pda.h
+++ b/arch/x86/include/asm/pda.h
@@ -45,11 +45,11 @@ extern void pda_init(int);
 
 #define cpu_pda(cpu)            (&per_cpu(__pda, cpu))
 
-#define read_pda(field)         x86_read_percpu(__pda.field)
-#define write_pda(field, val)   x86_write_percpu(__pda.field, val)
-#define add_pda(field, val)     x86_add_percpu(__pda.field, val)
-#define sub_pda(field, val)     x86_sub_percpu(__pda.field, val)
-#define or_pda(field, val)      x86_or_percpu(__pda.field, val)
+#define read_pda(field)         percpu_read(__pda.field)
+#define write_pda(field, val)   percpu_write(__pda.field, val)
+#define add_pda(field, val)     percpu_add(__pda.field, val)
+#define sub_pda(field, val)     percpu_sub(__pda.field, val)
+#define or_pda(field, val)      percpu_or(__pda.field, val)
 
 /* This is not atomic against other CPUs -- CPU preemption needs to be off */
 #define test_and_clear_bit_pda(bit, field)                              \
diff --git a/arch/x86/include/asm/percpu.h b/arch/x86/include/asm/percpu.h
index 328b31a429d7..03aa4b00a1c3 100644
--- a/arch/x86/include/asm/percpu.h
+++ b/arch/x86/include/asm/percpu.h
@@ -40,16 +40,11 @@
 
 #ifdef CONFIG_SMP
 #define __percpu_seg_str        "%%"__stringify(__percpu_seg)":"
-#define __my_cpu_offset         x86_read_percpu(this_cpu_off)
+#define __my_cpu_offset         percpu_read(this_cpu_off)
 #else
 #define __percpu_seg_str
 #endif
 
-#include <asm-generic/percpu.h>
-
-/* We can use this directly for local CPU (faster). */
-DECLARE_PER_CPU(unsigned long, this_cpu_off);
-
 /* For arch-specific code, we can use direct single-insn ops (they
  * don't give an lvalue though). */
 extern void __bad_percpu_size(void);
@@ -115,11 +110,13 @@ do {							\
         ret__;                                          \
 })
 
-#define x86_read_percpu(var) percpu_from_op("mov", per_cpu__##var)
-#define x86_write_percpu(var, val) percpu_to_op("mov", per_cpu__##var, val)
-#define x86_add_percpu(var, val) percpu_to_op("add", per_cpu__##var, val)
-#define x86_sub_percpu(var, val) percpu_to_op("sub", per_cpu__##var, val)
-#define x86_or_percpu(var, val) percpu_to_op("or", per_cpu__##var, val)
+#define percpu_read(var)        percpu_from_op("mov", per_cpu__##var)
+#define percpu_write(var, val)  percpu_to_op("mov", per_cpu__##var, val)
+#define percpu_add(var, val)    percpu_to_op("add", per_cpu__##var, val)
+#define percpu_sub(var, val)    percpu_to_op("sub", per_cpu__##var, val)
+#define percpu_and(var, val)    percpu_to_op("and", per_cpu__##var, val)
+#define percpu_or(var, val)     percpu_to_op("or", per_cpu__##var, val)
+#define percpu_xor(var, val)    percpu_to_op("xor", per_cpu__##var, val)
 
 /* This is not atomic against other CPUs -- CPU preemption needs to be off */
 #define x86_test_and_clear_bit_percpu(bit, var)                         \
@@ -131,6 +128,11 @@ do {							\
         old__;                                                          \
 })
 
+#include <asm-generic/percpu.h>
+
+/* We can use this directly for local CPU (faster). */
+DECLARE_PER_CPU(unsigned long, this_cpu_off);
+
 #ifdef CONFIG_X86_64
 extern void load_pda_offset(int cpu);
 #else
diff --git a/arch/x86/include/asm/smp.h b/arch/x86/include/asm/smp.h
index 127415402ea1..c7bbbbe65d3f 100644
--- a/arch/x86/include/asm/smp.h
+++ b/arch/x86/include/asm/smp.h
@@ -160,7 +160,7 @@ extern unsigned disabled_cpus __cpuinitdata;
  * from the initial startup. We map APIC_BASE very early in page_setup(),
  * so this is correct in the x86 case.
  */
-#define raw_smp_processor_id() (x86_read_percpu(cpu_number))
+#define raw_smp_processor_id() (percpu_read(cpu_number))
 extern int safe_smp_processor_id(void);
 
 #elif defined(CONFIG_X86_64_SMP)
diff --git a/arch/x86/kernel/process_32.c b/arch/x86/kernel/process_32.c
index a546f55c77b4..77d546817d94 100644
--- a/arch/x86/kernel/process_32.c
+++ b/arch/x86/kernel/process_32.c
@@ -591,7 +591,7 @@ __switch_to(struct task_struct *prev_p, struct task_struct *next_p)
         if (prev->gs | next->gs)
                 loadsegment(gs, next->gs);
 
-        x86_write_percpu(current_task, next_p);
+        percpu_write(current_task, next_p);
 
         return prev_p;
 }
diff --git a/arch/x86/kernel/tlb_32.c b/arch/x86/kernel/tlb_32.c
index ec53818f4e38..e65449d0f7d9 100644
--- a/arch/x86/kernel/tlb_32.c
+++ b/arch/x86/kernel/tlb_32.c
@@ -34,8 +34,8 @@ static DEFINE_SPINLOCK(tlbstate_lock);
  */
 void leave_mm(int cpu)
 {
-        BUG_ON(x86_read_percpu(cpu_tlbstate.state) == TLBSTATE_OK);
-        cpu_clear(cpu, x86_read_percpu(cpu_tlbstate.active_mm)->cpu_vm_mask);
+        BUG_ON(percpu_read(cpu_tlbstate.state) == TLBSTATE_OK);
+        cpu_clear(cpu, percpu_read(cpu_tlbstate.active_mm)->cpu_vm_mask);
         load_cr3(swapper_pg_dir);
 }
 EXPORT_SYMBOL_GPL(leave_mm);
@@ -103,8 +103,8 @@ void smp_invalidate_interrupt(struct pt_regs *regs)
                  * BUG();
                  */
 
-        if (flush_mm == x86_read_percpu(cpu_tlbstate.active_mm)) {
-                if (x86_read_percpu(cpu_tlbstate.state) == TLBSTATE_OK) {
+        if (flush_mm == percpu_read(cpu_tlbstate.active_mm)) {
+                if (percpu_read(cpu_tlbstate.state) == TLBSTATE_OK) {
                         if (flush_va == TLB_FLUSH_ALL)
                                 local_flush_tlb();
                         else
@@ -222,7 +222,7 @@ static void do_flush_tlb_all(void *info)
         unsigned long cpu = smp_processor_id();
 
         __flush_tlb_all();
-        if (x86_read_percpu(cpu_tlbstate.state) == TLBSTATE_LAZY)
+        if (percpu_read(cpu_tlbstate.state) == TLBSTATE_LAZY)
                 leave_mm(cpu);
 }
 
diff --git a/arch/x86/mach-voyager/voyager_smp.c b/arch/x86/mach-voyager/voyager_smp.c
index 1a48368acb09..96f15b09a4c5 100644
--- a/arch/x86/mach-voyager/voyager_smp.c
+++ b/arch/x86/mach-voyager/voyager_smp.c
@@ -402,7 +402,7 @@ void __init find_smp_config(void)
              VOYAGER_SUS_IN_CONTROL_PORT);
 
         current_thread_info()->cpu = boot_cpu_id;
-        x86_write_percpu(cpu_number, boot_cpu_id);
+        percpu_write(cpu_number, boot_cpu_id);
 }
 
 /*
@@ -1782,7 +1782,7 @@ static void __init voyager_smp_cpus_done(unsigned int max_cpus)
 void __init smp_setup_processor_id(void)
 {
         current_thread_info()->cpu = hard_smp_processor_id();
-        x86_write_percpu(cpu_number, hard_smp_processor_id());
+        percpu_write(cpu_number, hard_smp_processor_id());
 }
 
 static void voyager_send_call_func(cpumask_t callmask)
diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
index 312414ef9365..75b94139e1f2 100644
--- a/arch/x86/xen/enlighten.c
+++ b/arch/x86/xen/enlighten.c
@@ -695,17 +695,17 @@ static void xen_write_cr0(unsigned long cr0)
 
 static void xen_write_cr2(unsigned long cr2)
 {
-        x86_read_percpu(xen_vcpu)->arch.cr2 = cr2;
+        percpu_read(xen_vcpu)->arch.cr2 = cr2;
 }
 
 static unsigned long xen_read_cr2(void)
 {
-        return x86_read_percpu(xen_vcpu)->arch.cr2;
+        return percpu_read(xen_vcpu)->arch.cr2;
 }
 
 static unsigned long xen_read_cr2_direct(void)
 {
-        return x86_read_percpu(xen_vcpu_info.arch.cr2);
+        return percpu_read(xen_vcpu_info.arch.cr2);
 }
 
 static void xen_write_cr4(unsigned long cr4)
@@ -718,12 +718,12 @@ static void xen_write_cr4(unsigned long cr4)
 
 static unsigned long xen_read_cr3(void)
 {
-        return x86_read_percpu(xen_cr3);
+        return percpu_read(xen_cr3);
 }
 
 static void set_current_cr3(void *v)
 {
-        x86_write_percpu(xen_current_cr3, (unsigned long)v);
+        percpu_write(xen_current_cr3, (unsigned long)v);
 }
 
 static void __xen_write_cr3(bool kernel, unsigned long cr3)
@@ -748,7 +748,7 @@ static void __xen_write_cr3(bool kernel, unsigned long cr3)
         MULTI_mmuext_op(mcs.mc, op, 1, NULL, DOMID_SELF);
 
         if (kernel) {
-                x86_write_percpu(xen_cr3, cr3);
+                percpu_write(xen_cr3, cr3);
 
                 /* Update xen_current_cr3 once the batch has actually
                    been submitted. */
@@ -764,7 +764,7 @@ static void xen_write_cr3(unsigned long cr3)
 
         /* Update while interrupts are disabled, so its atomic with
            respect to ipis */
-        x86_write_percpu(xen_cr3, cr3);
+        percpu_write(xen_cr3, cr3);
 
         __xen_write_cr3(true, cr3);
 
diff --git a/arch/x86/xen/irq.c b/arch/x86/xen/irq.c
index bb042608c602..2e8271431e1a 100644
--- a/arch/x86/xen/irq.c
+++ b/arch/x86/xen/irq.c
@@ -39,7 +39,7 @@ static unsigned long xen_save_fl(void)
         struct vcpu_info *vcpu;
         unsigned long flags;
 
-        vcpu = x86_read_percpu(xen_vcpu);
+        vcpu = percpu_read(xen_vcpu);
 
         /* flag has opposite sense of mask */
         flags = !vcpu->evtchn_upcall_mask;
@@ -62,7 +62,7 @@ static void xen_restore_fl(unsigned long flags)
            make sure we're don't switch CPUs between getting the vcpu
            pointer and updating the mask. */
         preempt_disable();
-        vcpu = x86_read_percpu(xen_vcpu);
+        vcpu = percpu_read(xen_vcpu);
         vcpu->evtchn_upcall_mask = flags;
         preempt_enable_no_resched();
 
@@ -83,7 +83,7 @@ static void xen_irq_disable(void)
            make sure we're don't switch CPUs between getting the vcpu
            pointer and updating the mask. */
         preempt_disable();
-        x86_read_percpu(xen_vcpu)->evtchn_upcall_mask = 1;
+        percpu_read(xen_vcpu)->evtchn_upcall_mask = 1;
         preempt_enable_no_resched();
 }
 
@@ -96,7 +96,7 @@ static void xen_irq_enable(void)
            the caller is confused and is trying to re-enable interrupts
            on an indeterminate processor. */
 
-        vcpu = x86_read_percpu(xen_vcpu);
+        vcpu = percpu_read(xen_vcpu);
         vcpu->evtchn_upcall_mask = 0;
 
         /* Doesn't matter if we get preempted here, because any
diff --git a/arch/x86/xen/mmu.c b/arch/x86/xen/mmu.c
index 503c240e26c7..7bc7852cc5c4 100644
--- a/arch/x86/xen/mmu.c
+++ b/arch/x86/xen/mmu.c
@@ -1074,7 +1074,7 @@ static void drop_other_mm_ref(void *info)
 
         /* If this cpu still has a stale cr3 reference, then make sure
            it has been flushed. */
-        if (x86_read_percpu(xen_current_cr3) == __pa(mm->pgd)) {
+        if (percpu_read(xen_current_cr3) == __pa(mm->pgd)) {
                 load_cr3(swapper_pg_dir);
                 arch_flush_lazy_cpu_mode();
         }
diff --git a/arch/x86/xen/multicalls.h b/arch/x86/xen/multicalls.h
index 858938241616..e786fa7f2615 100644
--- a/arch/x86/xen/multicalls.h
+++ b/arch/x86/xen/multicalls.h
@@ -39,7 +39,7 @@ static inline void xen_mc_issue(unsigned mode)
                 xen_mc_flush();
 
         /* restore flags saved in xen_mc_batch */
-        local_irq_restore(x86_read_percpu(xen_mc_irq_flags));
+        local_irq_restore(percpu_read(xen_mc_irq_flags));
 }
 
 /* Set up a callback to be called when the current batch is flushed */
diff --git a/arch/x86/xen/smp.c b/arch/x86/xen/smp.c
index 83fa4236477d..3bfd6dd0b47c 100644
--- a/arch/x86/xen/smp.c
+++ b/arch/x86/xen/smp.c
@@ -78,7 +78,7 @@ static __cpuinit void cpu_bringup(void)
         xen_setup_cpu_clockevents();
 
         cpu_set(cpu, cpu_online_map);
-        x86_write_percpu(cpu_state, CPU_ONLINE);
+        percpu_write(cpu_state, CPU_ONLINE);
         wmb();
 
         /* We can take interrupts now: we're officially "up". */
diff --git a/include/asm-generic/percpu.h b/include/asm-generic/percpu.h
index b0e63c672ebd..00f45ff081a6 100644
--- a/include/asm-generic/percpu.h
+++ b/include/asm-generic/percpu.h
@@ -80,4 +80,56 @@ extern void setup_per_cpu_areas(void);
 #define DECLARE_PER_CPU(type, name) extern PER_CPU_ATTRIBUTES \
                                         __typeof__(type) per_cpu_var(name)
 
+/*
+ * Optional methods for optimized non-lvalue per-cpu variable access.
+ *
+ * @var can be a percpu variable or a field of it and its size should
+ * equal char, int or long.  percpu_read() evaluates to a lvalue and
+ * all others to void.
+ *
+ * These operations are guaranteed to be atomic w.r.t. preemption.
+ * The generic versions use plain get/put_cpu_var().  Archs are
+ * encouraged to implement single-instruction alternatives which don't
+ * require preemption protection.
+ */
+#ifndef percpu_read
+# define percpu_read(var)                                               \
+  ({                                                                    \
+        typeof(per_cpu_var(var)) __tmp_var__;                           \
+        __tmp_var__ = get_cpu_var(var);                                 \
+        put_cpu_var(var);                                               \
+        __tmp_var__;                                                    \
+  })
+#endif
+
+#define __percpu_generic_to_op(var, val, op)                            \
+do {                                                                    \
+        get_cpu_var(var) op val;                                        \
+        put_cpu_var(var);                                               \
+} while (0)
+
+#ifndef percpu_write
+# define percpu_write(var, val)         __percpu_generic_to_op(var, (val), =)
+#endif
+
+#ifndef percpu_add
+# define percpu_add(var, val)           __percpu_generic_to_op(var, (val), +=)
+#endif
+
+#ifndef percpu_sub
+# define percpu_sub(var, val)           __percpu_generic_to_op(var, (val), -=)
+#endif
+
+#ifndef percpu_and
+# define percpu_and(var, val)           __percpu_generic_to_op(var, (val), &=)
+#endif
+
+#ifndef percpu_or
+# define percpu_or(var, val)            __percpu_generic_to_op(var, (val), |=)
+#endif
+
+#ifndef percpu_xor
+# define percpu_xor(var, val)           __percpu_generic_to_op(var, (val), ^=)
+#endif
+
 #endif /* _ASM_GENERIC_PERCPU_H_ */