tunables: Simplify TUNABLE_SET interface

The TUNABLE_SET interface took a primitive C type argument, which
resulted in inconsistent type conversions internally due to incorrect
dereferencing of types, especialy on 32-bit architectures.  This
change simplifies the TUNABLE setting logic along with the interfaces.

Now all numeric tunable values are stored as signed numbers in
tunable_num_t, which is intmax_t.  All calls to set tunables cast the
input value to its primitive type and then to tunable_num_t for
storage.  This relies on gcc-specific (although I suspect other
compilers woul also do the same) unsigned to signed integer conversion
semantics, i.e. the bit pattern is conserved.  The reverse conversion
is guaranteed by the standard.

1 files changed, 7 insertions, 9 deletions

diff --git a/manual/README.tunables b/manual/README.tunables
index d8c768abcc..605ddd78cd 100644
--- a/manual/README.tunables
+++ b/manual/README.tunables
@@ -98,17 +98,16 @@ where it can expect the tunable value to be passed in VALP.
 
 Tunables in the module can be updated using:
 
-  TUNABLE_SET (check, int32_t, val)
+  TUNABLE_SET (check, val)
 
-where 'check' is the tunable name, 'int32_t' is the C type of the tunable and
-'val' is a value of same type.
+where 'check' is the tunable name and 'val' is a value of same type.
 
 To get and set tunables in a different namespace from that module, use the full
 form of the macros as follows:
 
   val = TUNABLE_GET_FULL (glibc, cpu, hwcap_mask, uint64_t, NULL)
 
-  TUNABLE_SET_FULL (glibc, cpu, hwcap_mask, uint64_t, val)
+  TUNABLE_SET_FULL (glibc, cpu, hwcap_mask, val)
 
 where 'glibc' is the top namespace, 'cpu' is the tunable namespace and the
 remaining arguments are the same as the short form macros.
@@ -116,18 +115,17 @@ remaining arguments are the same as the short form macros.
 The minimum and maximum values can updated together with the tunable value
 using:
 
-  TUNABLE_SET_WITH_BOUNDS (check, int32_t, val, min, max)
+  TUNABLE_SET_WITH_BOUNDS (check, val, min, max)
 
-where 'check' is the tunable name, 'int32_t' is the C type of the tunable,
-'val' is a value of same type, 'min' and 'max' are the minimum and maximum
-values of the tunable.
+where 'check' is the tunable name, 'val' is a value of same type, 'min' and
+'max' are the minimum and maximum values of the tunable.
 
 To set the minimum and maximum values of tunables in a different namespace
 from that module, use the full form of the macros as follows:
 
   val = TUNABLE_GET_FULL (glibc, cpu, hwcap_mask, uint64_t, NULL)
 
-  TUNABLE_SET_WITH_BOUNDS_FULL (glibc, cpu, hwcap_mask, uint64_t, val, min, max)
+  TUNABLE_SET_WITH_BOUNDS_FULL (glibc, cpu, hwcap_mask, val, min, max)
 
 where 'glibc' is the top namespace, 'cpu' is the tunable namespace and the
 remaining arguments are the same as the short form macros.