percpu: Generic support for this_cpu_cmpxchg_double()

Introduce this_cpu_cmpxchg_double().  this_cpu_cmpxchg_double() allows
the comparison between two consecutive words and replaces them if
there is a match.

	bool this_cpu_cmpxchg_double(pcp1, pcp2,
		old_word1, old_word2, new_word1, new_word2)

this_cpu_cmpxchg_double does not return the old value (difficult since
there are two words) but a boolean indicating if the operation was
successful.

The first percpu variable must be double word aligned!

-tj: Updated to return bool instead of int, converted size check to
     BUILD_BUG_ON() instead of VM_BUG_ON() and other cosmetic changes.

Signed-off-by: Christoph Lameter <cl@linux.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

1 files changed, 128 insertions, 0 deletions

diff --git a/include/linux/percpu.h b/include/linux/percpu.h
index 27c3c6fcfad3..3a5c4449fd36 100644
--- a/include/linux/percpu.h
+++ b/include/linux/percpu.h
@@ -255,6 +255,30 @@ extern void __bad_size_call_parameter(void);
         pscr2_ret__;                                                    \
 })
 
+/*
+ * Special handling for cmpxchg_double.  cmpxchg_double is passed two
+ * percpu variables.  The first has to be aligned to a double word
+ * boundary and the second has to follow directly thereafter.
+ */
+#define __pcpu_double_call_return_bool(stem, pcp1, pcp2, ...)           \
+({                                                                      \
+        bool pdcrb_ret__;                                               \
+        __verify_pcpu_ptr(&pcp1);                                       \
+        BUILD_BUG_ON(sizeof(pcp1) != sizeof(pcp2));                     \
+        VM_BUG_ON((unsigned long)(&pcp1) % (2 * sizeof(pcp1)));         \
+        VM_BUG_ON((unsigned long)(&pcp2) !=                             \
+                  (unsigned long)(&pcp1) + sizeof(pcp1));               \
+        switch(sizeof(pcp1)) {                                          \
+        case 1: pdcrb_ret__ = stem##1(pcp1, pcp2, __VA_ARGS__); break;  \
+        case 2: pdcrb_ret__ = stem##2(pcp1, pcp2, __VA_ARGS__); break;  \
+        case 4: pdcrb_ret__ = stem##4(pcp1, pcp2, __VA_ARGS__); break;  \
+        case 8: pdcrb_ret__ = stem##8(pcp1, pcp2, __VA_ARGS__); break;  \
+        default:                                                        \
+                __bad_size_call_parameter(); break;                     \
+        }                                                               \
+        pdcrb_ret__;                                                    \
+})
+
 #define __pcpu_size_call(stem, variable, ...)                           \
 do {                                                                    \
         __verify_pcpu_ptr(&(variable));                                 \
@@ -501,6 +525,45 @@ do {									\
 #endif
 
 /*
+ * cmpxchg_double replaces two adjacent scalars at once.  The first
+ * two parameters are per cpu variables which have to be of the same
+ * size.  A truth value is returned to indicate success or failure
+ * (since a double register result is difficult to handle).  There is
+ * very limited hardware support for these operations, so only certain
+ * sizes may work.
+ */
+#define _this_cpu_generic_cmpxchg_double(pcp1, pcp2, oval1, oval2, nval1, nval2)        \
+({                                                                      \
+        int ret__;                                                      \
+        preempt_disable();                                              \
+        ret__ = __this_cpu_generic_cmpxchg_double(pcp1, pcp2,           \
+                        oval1, oval2, nval1, nval2);                    \
+        preempt_enable();                                               \
+        ret__;                                                          \
+})
+
+#ifndef this_cpu_cmpxchg_double
+# ifndef this_cpu_cmpxchg_double_1
+#  define this_cpu_cmpxchg_double_1(pcp1, pcp2, oval1, oval2, nval1, nval2)     \
+        _this_cpu_generic_cmpxchg_double(pcp1, pcp2, oval1, oval2, nval1, nval2)
+# endif
+# ifndef this_cpu_cmpxchg_double_2
+#  define this_cpu_cmpxchg_double_2(pcp1, pcp2, oval1, oval2, nval1, nval2)     \
+        _this_cpu_generic_cmpxchg_double(pcp1, pcp2, oval1, oval2, nval1, nval2)
+# endif
+# ifndef this_cpu_cmpxchg_double_4
+#  define this_cpu_cmpxchg_double_4(pcp1, pcp2, oval1, oval2, nval1, nval2)     \
+        _this_cpu_generic_cmpxchg_double(pcp1, pcp2, oval1, oval2, nval1, nval2)
+# endif
+# ifndef this_cpu_cmpxchg_double_8
+#  define this_cpu_cmpxchg_double_8(pcp1, pcp2, oval1, oval2, nval1, nval2)     \
+        _this_cpu_generic_cmpxchg_double(pcp1, pcp2, oval1, oval2, nval1, nval2)
+# endif
+# define this_cpu_cmpxchg_double(pcp1, pcp2, oval1, oval2, nval1, nval2)        \
+        __pcpu_double_call_return_bool(this_cpu_cmpxchg_double_, (pcp1), (pcp2), (oval1), (oval2), (nval1), (nval2))
+#endif
+
+/*
  * Generic percpu operations that do not require preemption handling.
  * Either we do not care about races or the caller has the
  * responsibility of handling preemptions issues. Arch code can still
@@ -703,6 +766,39 @@ do {									\
         __pcpu_size_call_return2(__this_cpu_cmpxchg_, pcp, oval, nval)
 #endif
 
+#define __this_cpu_generic_cmpxchg_double(pcp1, pcp2, oval1, oval2, nval1, nval2)       \
+({                                                                      \
+        int __ret = 0;                                                  \
+        if (__this_cpu_read(pcp1) == (oval1) &&                         \
+                         __this_cpu_read(pcp2)  == (oval2)) {           \
+                __this_cpu_write(pcp1, (nval1));                        \
+                __this_cpu_write(pcp2, (nval2));                        \
+                __ret = 1;                                              \
+        }                                                               \
+        (__ret);                                                        \
+})
+
+#ifndef __this_cpu_cmpxchg_double
+# ifndef __this_cpu_cmpxchg_double_1
+#  define __this_cpu_cmpxchg_double_1(pcp1, pcp2, oval1, oval2, nval1, nval2)   \
+        __this_cpu_generic_cmpxchg_double(pcp1, pcp2, oval1, oval2, nval1, nval2)
+# endif
+# ifndef __this_cpu_cmpxchg_double_2
+#  define __this_cpu_cmpxchg_double_2(pcp1, pcp2, oval1, oval2, nval1, nval2)   \
+        __this_cpu_generic_cmpxchg_double(pcp1, pcp2, oval1, oval2, nval1, nval2)
+# endif
+# ifndef __this_cpu_cmpxchg_double_4
+#  define __this_cpu_cmpxchg_double_4(pcp1, pcp2, oval1, oval2, nval1, nval2)   \
+        __this_cpu_generic_cmpxchg_double(pcp1, pcp2, oval1, oval2, nval1, nval2)
+# endif
+# ifndef __this_cpu_cmpxchg_double_8
+#  define __this_cpu_cmpxchg_double_8(pcp1, pcp2, oval1, oval2, nval1, nval2)   \
+        __this_cpu_generic_cmpxchg_double(pcp1, pcp2, oval1, oval2, nval1, nval2)
+# endif
+# define __this_cpu_cmpxchg_double(pcp1, pcp2, oval1, oval2, nval1, nval2)      \
+        __pcpu_double_call_return_bool(__this_cpu_cmpxchg_double_, (pcp1), (pcp2), (oval1), (oval2), (nval1), (nval2))
+#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
@@ -823,4 +919,36 @@ do {									\
         __pcpu_size_call_return2(irqsafe_cpu_cmpxchg_, (pcp), oval, nval)
 #endif
 
+#define irqsafe_generic_cpu_cmpxchg_double(pcp1, pcp2, oval1, oval2, nval1, nval2)      \
+({                                                                      \
+        int ret__;                                                      \
+        unsigned long flags;                                            \
+        local_irq_save(flags);                                          \
+        ret__ = __this_cpu_generic_cmpxchg_double(pcp1, pcp2,           \
+                        oval1, oval2, nval1, nval2);                    \
+        local_irq_restore(flags);                                       \
+        ret__;                                                          \
+})
+
+#ifndef irqsafe_cpu_cmpxchg_double
+# ifndef irqsafe_cpu_cmpxchg_double_1
+#  define irqsafe_cpu_cmpxchg_double_1(pcp1, pcp2, oval1, oval2, nval1, nval2)  \
+        irqsafe_generic_cpu_cmpxchg_double(pcp1, pcp2, oval1, oval2, nval1, nval2)
+# endif
+# ifndef irqsafe_cpu_cmpxchg_double_2
+#  define irqsafe_cpu_cmpxchg_double_2(pcp1, pcp2, oval1, oval2, nval1, nval2)  \
+        irqsafe_generic_cpu_cmpxchg_double(pcp1, pcp2, oval1, oval2, nval1, nval2)
+# endif
+# ifndef irqsafe_cpu_cmpxchg_double_4
+#  define irqsafe_cpu_cmpxchg_double_4(pcp1, pcp2, oval1, oval2, nval1, nval2)  \
+        irqsafe_generic_cpu_cmpxchg_double(pcp1, pcp2, oval1, oval2, nval1, nval2)
+# endif
+# ifndef irqsafe_cpu_cmpxchg_double_8
+#  define irqsafe_cpu_cmpxchg_double_8(pcp1, pcp2, oval1, oval2, nval1, nval2)  \
+        irqsafe_generic_cpu_cmpxchg_double(pcp1, pcp2, oval1, oval2, nval1, nval2)
+# endif
+# define irqsafe_cpu_cmpxchg_double(pcp1, pcp2, oval1, oval2, nval1, nval2)     \
+        __pcpu_double_call_return_int(irqsafe_cpu_cmpxchg_double_, (pcp1), (pcp2), (oval1), (oval2), (nval1), (nval2))
+#endif
+
 #endif /* __LINUX_PERCPU_H */