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Make dlerror(3) thread-safe.

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I gave up trying to use the usual thread-local buffer idiom; calls to
calloc(3) and free(3) from any of the "dl" functions -- which live in
the dynamic linker -- end up resolving to the dynamic linker's stubs.
I tried to work around that, but was just making things more complicated.
This alternative costs us a well-known TLS slot (instead of the
dynamically-allocated TLS slot we'd have used otherwise, so no difference
there), plus an extra buffer inside every pthread_internal_t.

Bug: 5404023
Change-Id: Ie9614edd05b6d1eeaf7bf9172792d616c6361767
This commit is contained in:
Elliott Hughes
2012-10-16 15:54:46 -07:00
parent a9944cfe9e
commit 5419b94747
10 changed files with 124 additions and 94 deletions
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60
libc/private/ThreadLocalBuffer.h Normal file
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/*
* Copyright (C) 2012 The Android Open Source Project
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* * Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
#ifndef _BIONIC_THREAD_LOCAL_BUFFER_H_included
#define _BIONIC_THREAD_LOCAL_BUFFER_H_included
#include <malloc.h>
#include <pthread.h>
// libstdc++ currently contains __cxa_guard_acquire and __cxa_guard_release,
// so we make do with macros instead of a C++ class.
// TODO: move __cxa_guard_acquire and __cxa_guard_release into libc.
#define GLOBAL_INIT_THREAD_LOCAL_BUFFER(name) \
static pthread_once_t __bionic_tls_ ## name ## _once; \
static pthread_key_t __bionic_tls_ ## name ## _key; \
static void __bionic_tls_ ## name ## _key_destroy(void* buffer) { \
free(buffer); \
} \
static void __bionic_tls_ ## name ## _key_init() { \
pthread_key_create(&__bionic_tls_ ## name ## _key, __bionic_tls_ ## name ## _key_destroy); \
}
// Leaves "name_tls_buffer" and "name_tls_buffer_size" defined and initialized.
#define LOCAL_INIT_THREAD_LOCAL_BUFFER(type, name, byte_count) \
pthread_once(&__bionic_tls_ ## name ## _once, __bionic_tls_ ## name ## _key_init); \
type name ## _tls_buffer = \
reinterpret_cast<type>(pthread_getspecific(__bionic_tls_ ## name ## _key)); \
if (name ## _tls_buffer == NULL) { \
name ## _tls_buffer = reinterpret_cast<type>(calloc(1, byte_count)); \
pthread_setspecific(__bionic_tls_ ## name ## _key, name ## _tls_buffer); \
} \
const size_t name ## _tls_buffer_size __attribute__((unused)) = byte_count
#endif // _BIONIC_THREAD_LOCAL_BUFFER_H_included