diff options
author | Siddhesh Poyarekar <siddhesh@sourceware.org> | 2021-02-05 13:18:58 +0530 |
---|---|---|
committer | Siddhesh Poyarekar <siddhesh@sourceware.org> | 2021-02-10 19:08:33 +0530 |
commit | 61117bfa1b08ca048e6512c0652c568300fedf6a (patch) | |
tree | d752f7a8eec0c3a174c42f73f1e7927616d6d073 /manual | |
parent | e604a5e4bb61267c58e6b6179209efe74ab5f675 (diff) | |
download | glibc-61117bfa1b08ca048e6512c0652c568300fedf6a.zip glibc-61117bfa1b08ca048e6512c0652c568300fedf6a.tar.gz glibc-61117bfa1b08ca048e6512c0652c568300fedf6a.tar.bz2 |
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.
Diffstat (limited to 'manual')
-rw-r--r-- | manual/README.tunables | 16 |
1 files changed, 7 insertions, 9 deletions
diff --git a/manual/README.tunables b/manual/README.tunables index d8c768a..605ddd7 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. |