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authorSiddhesh Poyarekar <siddhesh@sourceware.org>2017-06-01 20:24:46 +0530
committerSiddhesh Poyarekar <siddhesh@sourceware.org>2017-06-07 11:11:36 +0530
commit44330b6d32904fdc8b6835a112e0ba0aee9f4ef3 (patch)
treecac22bbc37efa02de8375e7c489d8380fcdce61f /elf/Versions
parentd4cc385c6e4161897de9f6e73413132d41f66ba3 (diff)
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tunables: Clean up hooks to get and set tunables
The TUNABLE_SET_VALUE and family of macros (and my later attempt to add a TUNABLE_GET) never quite went together very well because the overall interface was not clearly defined. This patch is an attempt to do just that. This patch consolidates the API to two simple sets of macros, TUNABLE_GET* and TUNABLE_SET*. If TUNABLE_NAMESPACE is defined, TUNABLE_GET takes just the tunable name, type and a (optionally NULL) callback function to get the value of the tunable. The callback function, if non-NULL, is called if the tunable was externally set (i.e. via GLIBC_TUNABLES or any future mechanism). For example: val = TUNABLE_GET (check, int32_t, check_callback) returns the value of the glibc.malloc.check tunable (assuming TUNABLE_NAMESPACE is set to malloc) as an int32_t into VAL after calling check_callback. Likewise, TUNABLE_SET can be used to set the value of the tunable, although this is currently possible only in the dynamic linker before it relocates itself. For example: TUNABLE_SET (check, int32_t, 2) will set glibc.malloc.check to 2. Of course, this is not possible since we set (or read) glibc.malloc.check long after it is relocated. To access or set a tunable outside of TUNABLE_NAMESPACE, use the TUNABLE_GET_FULL and TUNABLE_SET_FULL macros, which have the following prototype: TUNABLE_GET_FULL (glibc, tune, hwcap_mask, uint64_t, NULL) TUNABLE_SET_FULL (glibc, tune, hwcap_mask, uint64_t, 0xffff) In future the tunable list may get split into mutable and immutable tunables where mutable tunables can be modified by the library and userspace after relocation as well and TUNABLE_SET will be more useful than it currently is. However whenever we actually do that split, we will have to ensure that the mutable tunables are protected with locks. * elf/Versions (__tunable_set_val): Rename to __tunable_get_val. * elf/dl-tunables.c: Likewise. (do_tunable_update_val): New function. (__tunable_set_val): New function. (__tunable_get_val): Call CB only if the tunable was externally initialized. (tunables_strtoul): Replace strval with initialized. * elf/dl-tunables.h (strval): Replace with a bool initialized. (TUNABLE_ENUM_NAME, TUNABLE_ENUM_NAME1): Adjust names to prevent collision. (__tunable_set_val): New function. (TUNABLE_GET, TUNABLE_GET_FULL): New macros. (TUNABLE_SET, TUNABLE_SET_FULL): Likewise. (TUNABLE_SET_VAL): Remove. (TUNABLE_SET_VAL_WITH_CALLBACK): Likewise. * README.tunables: Document the new macros. * malloc/arena.c (ptmalloc_init): Adjust.
Diffstat (limited to 'elf/Versions')
-rw-r--r--elf/Versions2
1 files changed, 1 insertions, 1 deletions
diff --git a/elf/Versions b/elf/Versions
index 6abe9db8bd..c59facdbd7 100644
--- a/elf/Versions
+++ b/elf/Versions
@@ -72,6 +72,6 @@ ld {
_dl_signal_error; _dl_catch_error;
# Set value of a tunable.
- __tunable_set_val;
+ __tunable_get_val;
}
}