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/*
* Copyright 2019 The Emscripten Authors. All rights reserved.
* Emscripten is available under two separate licenses, the MIT license and the
* University of Illinois/NCSA Open Source License. Both these licenses can be
* found in the LICENSE file.
*/
#include <emscripten/heap.h>
#include <emscripten/threading.h>
#include <emscripten/console.h>
#include <stdlib.h>
#include <malloc.h>
#include "pthread_impl.h"
// Uncomment to trace TLS allocations.
// #define DEBUG_TLS
#ifdef DEBUG_TLS
#define dbg(fmt, ...) emscripten_dbgf(fmt, ##__VA_ARGS__)
#else
#define dbg(fmt, ...)
#endif
// linker-generated symbol that loads static TLS data at the given location.
extern void __wasm_init_tls(void *memory);
extern int __dso_handle;
// Create a thread-local wasm global which signal that the current thread is non
// to use the primary/static TLS region. Once this gets set it forces that all
// future calls to emscripten_tls_init to dynamically allocate TLS.
// This is needed because emscripten re-uses module instances owned by the
// worker for new pthreads. This in turn means that stale values of __tls_base
// from a previous pthreads need to be ignored.
// If this global is true then TLS needs to be dyanically allocated, if its
// flase we are free to use the existing/global __tls_base.
__asm__(".globaltype g_needs_dynamic_alloc, i32\n"
"g_needs_dynamic_alloc:\n");
static void set_needs_dynamic_alloc(void) {
__asm__("i32.const 1\n"
"global.set g_needs_dynamic_alloc\n");
}
static int needs_dynamic_alloc(void) {
int val;
__asm__("global.get g_needs_dynamic_alloc\n"
"local.set %0" : "=r" (val));
return val;
}
void _emscripten_tls_free() {
void* tls_block = __builtin_wasm_tls_base();
if (tls_block && needs_dynamic_alloc()) {
dbg("tls free: dso=%p <- %p", &__dso_handle, tls_block);
emscripten_builtin_free(tls_block);
}
}
void* _emscripten_tls_init(void) {
size_t tls_size = __builtin_wasm_tls_size();
void* tls_block = __builtin_wasm_tls_base();
if (pthread_self()->tls_base) {
// The TLS block for the main module is allocated alongside the pthread
// itself and its stack.
tls_block = pthread_self()->tls_base;
pthread_self()->tls_base = NULL;
} else if (needs_dynamic_alloc() || (!tls_block && tls_size)) {
// For non-main modules we do a dynamic allocation.
set_needs_dynamic_alloc();
tls_block = emscripten_builtin_memalign(__builtin_wasm_tls_align(), tls_size);
}
dbg("tls init: size=%zu dso=%p -> %p:%p", tls_size, &__dso_handle, tls_block, ((char*)tls_block)+tls_size);
__wasm_init_tls(tls_block);
return tls_block;
}
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