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SubjectRe: [this_cpu_xx V7 0/8] Per cpu atomics in core allocators and cleanup
On Thu, 17 Dec 2009, Mathieu Desnoyers wrote:

> Sure, can you point me to a git tree I should work on top of which
> includes the per cpu infrastructure to extend ?

Linus' git tree contains what yoou need. I have a early draft here of a
patch to implement the generic portions. Unfinished. I hope I have time to
complete this. Feel free to complete it but keep me posted so that I wont
repeat anything you do.

The modifications to asm-generic/cmpxchg-local wont work since we need to
do this_cpu_ptr() pointer calculations within the protected sections. I
was in the middle of getting rid of it when I found it was time to go
home...


---
include/asm-generic/cmpxchg-local.h | 24 ++++-
include/linux/percpu.h | 151 ++++++++++++++++++++++++++++++++++++
2 files changed, 169 insertions(+), 6 deletions(-)
Index: linux-2.6/include/asm-generic/cmpxchg-local.h
===================================================================
--- linux-2.6.orig/include/asm-generic/cmpxchg-local.h 2009-12-17 17:44:01.000000000 -0600
+++ linux-2.6/include/asm-generic/cmpxchg-local.h 2009-12-17 17:46:31.000000000 -0600
@@ -6,13 +6,12 @@
extern unsigned long wrong_size_cmpxchg(volatile void *ptr);

/*
- * Generic version of __cmpxchg_local (disables interrupts). Takes an unsigned
- * long parameter, supporting various types of architectures.
+ * Generic version of __cmpxchg_local.
*/
-static inline unsigned long __cmpxchg_local_generic(volatile void *ptr,
+static inline unsigned long ____cmpxchg_local_generic(volatile void *ptr,
unsigned long old, unsigned long new, int size)
{
- unsigned long flags, prev;
+ unsigned long prev;

/*
* Sanity checking, compile-time.
@@ -20,7 +19,6 @@ static inline unsigned long __cmpxchg_lo
if (size == 8 && sizeof(unsigned long) != 8)
wrong_size_cmpxchg(ptr);

- local_irq_save(flags);
switch (size) {
case 1: prev = *(u8 *)ptr;
if (prev == old)
@@ -41,11 +39,25 @@ static inline unsigned long __cmpxchg_lo
default:
wrong_size_cmpxchg(ptr);
}
- local_irq_restore(flags);
return prev;
}

/*
+ * Generic version of __cmpxchg_local (disables interrupts). Takes an unsigned
+ * long parameter, supporting various types of architectures.
+ */
+static inline unsigned long __cmpxchg_local_generic(volatile void *ptr,
+ unsigned long old, unsigned long new, int size)
+{
+ unsigned long flags, r;
+
+ local_irq_save(flags);
+ r = ____cmpxchg_local_generic(ptr, old, new ,size);
+ local_irq_restore(flags);
+ return r;
+}
+
+/*
* Generic version of __cmpxchg64_local. Takes an u64 parameter.
*/
static inline u64 __cmpxchg64_local_generic(volatile void *ptr,
Index: linux-2.6/include/linux/percpu.h
===================================================================
--- linux-2.6.orig/include/linux/percpu.h 2009-12-17 17:31:10.000000000 -0600
+++ linux-2.6/include/linux/percpu.h 2009-12-17 18:23:02.000000000 -0600
@@ -443,6 +443,48 @@ do { \
# define this_cpu_xor(pcp, val) __pcpu_size_call(this_cpu_or_, (pcp), (val))
#endif

+#ifndef this_cpu_cmpxchg
+# ifndef this_cpu_cmpxchg_1
+# define this_cpu_cmpxchg_1(pcp, old, new) this_cpu_cmpxchg_generic(((pcp), (old), (new), 1)
+# endif
+# ifndef this_cpu_cmpxchg_2
+# define this_cpu_cmpxchg_2(pcp, old, new) this_cpu_cmpxchg_generic(((pcp), (old), (new), 2)
+# endif
+# ifndef this_cpu_cmpxchg_4
+# define this_cpu_cmpxchg_4(pcp, old, new) this_cpu_cmpxchg_generic(((pcp), (old), (new), 4)
+# endif
+# ifndef this_cpu_cmpxchg_8
+# define this_cpu_cmpxchg_8(pcp, old, new) this_cpu_cmpxchg_generic(((pcp), (old), (new), 8)
+# endif
+# define this_cpu_cmpxchg(pcp, old, new) __pcpu_size_call_return(this_cpu_cmpxchg_, (old), (new))
+#endif
+
+#define _this_cpu_generic_xchg_op(pcp, val) \
+ ({ \
+ typeof(*(var)) __tmp_var__; \
+ preempt_disable(); \
+ __tmp_var = __this_cpu_read(pcp); \
+ __this_cpu_read(pcp) = (val); \
+ preemt_enable(); \
+ __tmp_var__; \
+ })
+
+#ifndef this_cpu_xchg
+# ifndef this_cpu_xchg_1
+# define this_cpu_xchg_1(pcp, val) _this_cpu_generic_xchg_op((pcp), (val))
+# endif
+# ifndef this_cpu_xchg_2
+# define this_cpu_xchg_2(pcp, val) _this_cpu_generic_xchg_op((pcp), (val))
+# endif
+# ifndef this_cpu_xchg_4
+# define this_cpu_xchg_4(pcp, val) _this_cpu_generic_xchg_op((pcp), (val))
+# endif
+# ifndef this_cpu_xchg_8
+# define this_cpu_xchg_8(pcp, val) _this_cpu_generic_xchg_op((pcp), (val))
+# endif
+# define this_cpu_xchg(pcp, val) __pcpu_size_call_return(this_cpu_xchg_, (val))
+#endif
+
/*
* Generic percpu operations that do not require preemption handling.
* Either we do not care about races or the caller has the
@@ -594,6 +636,46 @@ do { \
# define __this_cpu_xor(pcp, val) __pcpu_size_call(__this_cpu_xor_, (pcp), (val))
#endif

+#ifndef __this_cpu_cmpxchg
+# ifndef __this_cpu_cmpxchg_1
+# define __this_cpu_cmpxchg _1(pcp, old, new) ____cmpxchg_local_generic(__this_cpu_ptr(pcp), (old), (new), 1)
+# endif
+# ifndef __this_cpu_cmpxchg_2
+# define __this_cpu_cmpxchg_2(pcp, old, new) ____cmpxchg_local_generic(__this_cpu_ptr(pcp), (old), (new), 2)
+# endif
+# ifndef __this_cpu_cmpxchg_4
+# define __this_cpu_cmpxchg_4(pcp, old, new) ____cmpxchg_local_generic(__this_cpu_ptr(pcp), (old), (new), 4)
+# endif
+# ifndef __this_cpu_cmpxchg_8
+# define __this_cpu_cmpxchg_8(pcp, old, new) ____cmpxchg_local_generic(__this_cpu_ptr(pcp), (old), (new), 8)
+# endif
+# define __this_cpu_cmpxchg(pcp, old, new) __pcpu_size_call_return(__this_cpu_cmpxchg_, (old), (new))
+#endif
+
+#define _this_cpu_generic_xchg_op(pcp, val) \
+ ({ \
+ typeof(*(var)) __tmp_var__; \
+ __tmp_var = __this_cpu_read(pcp); \
+ __this_cpu_write((pcp), val); \
+ __tmp_var__; \
+ })
+
+#ifndef __this_cpu_xchg
+# ifndef __this_cpu_xchg_1
+# define __this_cpu_xchg_1(pcp, val) __this_cpu_generic_xchg_op((pcp), (val))
+# endif
+# ifndef __this_cpu_xchg_2
+# define __this_cpu_xchg_2(pcp, val) __this_cpu_generic_xchg_op((pcp), (val))
+# endif
+# ifndef __this_cpu_xchg_4
+# define __this_cpu_xchg_4(pcp, val) __this_cpu_generic_xchg_op((pcp), (val))
+# endif
+# ifndef __this_cpu_xchg_8
+# define __this_cpu_xchg_8(pcp, val) __this_cpu_generic_xchg_op((pcp), (val))
+# endif
+# define __this_cpu_xchg(pcp, val) __pcpu_size_call_return(__this_cpu_xchg_, (val))
+#endif
+
/*
* IRQ safe versions of the per cpu RMW operations. Note that these operations
* are *not* safe against modification of the same variable from another
@@ -709,4 +791,73 @@ do { \
# define irqsafe_cpu_xor(pcp, val) __pcpu_size_call(irqsafe_cpu_xor_, (val))
#endif

+#ifndef irqsafe_cpu_cmpxchg
+# ifndef irqsafe_cpu_cmpxchg_1
+# define irqsafe_cpu_cmpxchg_1(pcp, old, new) __cmpxchg_local_generic(((pcp), (old), (new), 1)
+# endif
+# ifndef irqsafe_cpu_cmpxchg_2
+# define irqsafe_cpu_cmpxchg_2(pcp, old, new) __cmpxchg_local_generic(((pcp), (old), (new), 2)
+# endif
+# ifndef irqsafe_cpu_cmpxchg_4
+# define irqsafe_cpu_cmpxchg_4(pcp, old, new) __cmpxchg_local_generic(((pcp), (old), (new), 4)
+# endif
+# ifndef irqsafe_cpu_cmpxchg_8
+# define irqsafe_cpu_cmpxchg_8(pcp, old, new) __cmpxchg_local_generic(((pcp), (old), (new), 8)
+# endif
+# define irqsafe_cpu_cmpxchg(pcp, old, new) __pcpu_size_call_return(irqsafe_cpu_cmpxchg_, (old), (new))
+#endif
+
+#define irqsafe_generic_xchg_op(pcp, val) \
+ ({ \
+ typeof(*(var)) __tmp_var__; \
+ unsigned long flags; \
+ local_irq_disable(flags); \
+ __tmp_var = __this_cpu_read(pcp); \
+ __this_cpu_write(pcp, val); \
+ local_irq_enable(flags); \
+ __tmp_var__; \
+ })
+
+#ifndef irqsafe_cpu_xchg
+# ifndef irqsafe_cpu_xchg_1
+# define irqsafe_cpu_xchg_1(pcp, val) irqsafe_generic_xchg_op((pcp), (val))
+# endif
+# ifndef irqsafe_cpu_xchg_2
+# define irqsafe_cpu_xchg_2(pcp, val) irqsafe_generic_xchg_op((pcp), (val))
+# endif
+# ifndef irqsafe_cpu_xchg_4
+# define irqsafe_cpu_xchg_4(pcp, val) irqsafe_generic_xchg_op((pcp), (val))
+# endif
+# ifndef irqsafe_cpu_xchg_8
+# define irqsafe_cpu_xchg_8(pcp, val) irqsafe_generic_xchg_op((pcp), (val))
+# endif
+# define irqsafe_cpu_xchg(pcp, val) __pcpu_size_call_return(irqsafe_cpu_xchg_, (val))
+#endif
+
+#define _this_cpu_generic_add_return_op(pcp, val) \
+do { \
+ preempt_disable(); \
+ *__this_cpu_ptr(&pcp) op val; \
+ preempt_enable(); \
+} while (0)
+
+
+#ifndef this_cpu_add_return
+# ifndef this_cpu_add_return_1
+# define this_cpu_add_return_1(pcp, val) _this_cpu_generic_add_return_op((pcp), (val))
+# endif
+# ifndef this_cpu_ _2
+# define this_cpu_add_return_2(pcp, val) _this_cpu_generic_add_return_op((pcp), (val))
+# endif
+# ifndef this_cpu_add_return_4
+# define this_cpu_add_return_4(pcp, val) _this_cpu_generic_add_return_op((pcp), (val))
+# endif
+# ifndef this_cpu_add_return_8
+# define this_cpu_add_return_8(pcp, val) _this_cpu_generic_add_return_op((pcp), (val))
+# endif
+# define this_cpu_add_return(pcp, val) __pcpu_size_call_return(_cpu_ _, (val))
+#endif
+
+#ifndef irqsafe_cpu_add_return
+
#endif /* __LINUX_PERCPU_H */

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