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Revert "[base/platform] Simplify fast TLS on macOS"

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This reverts commit 9cdee4f418.

Reason for revert: https://ci.chromium.org/ui/p/v8/builders/ci/V8%20Mac64%20-%20debug/38658/overview

Original change's description:
> [base/platform] Simplify fast TLS on macOS
>
> Since the TLS offset is constant across all supported OS releases, we
> no longer need to adjust it, nor to read it at runtime. This also aligns
> the code in V8 with what is done in Chromium.
>
> Change-Id: I0f3c54da39a776406083c897de888f06c61852b8
> Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3599481
> Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
> Commit-Queue: Benoit Lize <lizeb@chromium.org>
> Cr-Commit-Position: refs/heads/main@{#80106}

Change-Id: Ie6371c2ad12ed6f63be51b819083a7c0c4e22751
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3602502
Auto-Submit: Tobias Tebbi <tebbi@chromium.org>
Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Commit-Queue: Tobias Tebbi <tebbi@chromium.org>
Owners-Override: Tobias Tebbi <tebbi@chromium.org>
Cr-Commit-Position: refs/heads/main@{#80108}
This commit is contained in:
Tobias Tebbi 2022-04-22 11:10:22 +00:00 committed by V8 LUCI CQ
parent e16af48cdd
commit 267b962d23
2 changed files with 68 additions and 12 deletions
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58
src/base/platform/platform-posix.cc
View File

@ -1130,7 +1130,47 @@ static pthread_key_t LocalKeyToPthreadKey(Thread::LocalStorageKey local_key) {
#endif
}
#if defined(V8_FAST_TLS_SUPPORTED) && defined(DEBUG)
#ifdef V8_FAST_TLS_SUPPORTED
static std::atomic<bool> tls_base_offset_initialized{false};
intptr_t kMacTlsBaseOffset = 0;
// It's safe to do the initialization more that once, but it has to be
// done at least once.
static void InitializeTlsBaseOffset() {
const size_t kBufferSize = 128;
char buffer[kBufferSize];
size_t buffer_size = kBufferSize;
int ctl_name[] = { CTL_KERN , KERN_OSRELEASE };
if (sysctl(ctl_name, 2, buffer, &buffer_size, nullptr, 0) != 0) {
FATAL("V8 failed to get kernel version");
}
// The buffer now contains a string of the form XX.YY.ZZ, where
// XX is the major kernel version component.
// Make sure the buffer is 0-terminated.
buffer[kBufferSize - 1] = '\0';
char* period_pos = strchr(buffer, '.');
*period_pos = '\0';
int kernel_version_major = static_cast<int>(strtol(buffer, nullptr, 10));
// The constants below are taken from pthreads.s from the XNU kernel
// sources archive at www.opensource.apple.com.
if (kernel_version_major < 11) {
// 8.x.x (Tiger), 9.x.x (Leopard), 10.x.x (Snow Leopard) have the
// same offsets.
#if V8_HOST_ARCH_IA32
kMacTlsBaseOffset = 0x48;
#else
kMacTlsBaseOffset = 0x60;
#endif
} else {
// 11.x.x (Lion) changed the offset.
kMacTlsBaseOffset = 0;
}
tls_base_offset_initialized.store(true, std::memory_order_release);
}
static void CheckFastTls(Thread::LocalStorageKey key) {
void* expected = reinterpret_cast<void*>(0x1234CAFE);
@ -1142,20 +1182,30 @@ static void CheckFastTls(Thread::LocalStorageKey key) {
Thread::SetThreadLocal(key, nullptr);
}
#endif // defined(V8_FAST_TLS_SUPPORTED) && defined(DEBUG)
#endif // V8_FAST_TLS_SUPPORTED
Thread::LocalStorageKey Thread::CreateThreadLocalKey() {
#ifdef V8_FAST_TLS_SUPPORTED
bool check_fast_tls = false;
if (!tls_base_offset_initialized.load(std::memory_order_acquire)) {
check_fast_tls = true;
InitializeTlsBaseOffset();
}
#endif
pthread_key_t key;
int result = pthread_key_create(&key, nullptr);
DCHECK_EQ(0, result);
USE(result);
LocalStorageKey local_key = PthreadKeyToLocalKey(key);
#if defined(V8_FAST_TLS_SUPPORTED) && defined(DEBUG)
CheckFastTls(local_key);
#ifdef V8_FAST_TLS_SUPPORTED
// If we just initialized fast TLS support, make sure it works.
if (check_fast_tls) CheckFastTls(local_key);
#endif
return local_key;
}
void Thread::DeleteThreadLocalKey(LocalStorageKey key) {
pthread_key_t pthread_key = LocalKeyToPthreadKey(key);
int result = pthread_key_delete(pthread_key);

22
src/base/platform/platform.h
View File

@ -71,7 +71,9 @@ namespace base {
#define V8_FAST_TLS_SUPPORTED 1
V8_INLINE intptr_t InternalGetExistingThreadLocal(intptr_t index) {
V8_INLINE intptr_t InternalGetExistingThreadLocal(intptr_t index);
inline intptr_t InternalGetExistingThreadLocal(intptr_t index) {
const intptr_t kTibInlineTlsOffset = 0xE10;
const intptr_t kTibExtraTlsOffset = 0xF94;
const intptr_t kMaxInlineSlots = 64;
@ -89,8 +91,6 @@ V8_INLINE intptr_t InternalGetExistingThreadLocal(intptr_t index) {
(index - kMaxInlineSlots));
}
// Not possible on ARM64, the register holding the base pointer is not stable
// across major releases.
#elif defined(__APPLE__) && (V8_HOST_ARCH_IA32 || V8_HOST_ARCH_X64)
// tvOS simulator does not use intptr_t as TLS key.
@ -98,14 +98,20 @@ V8_INLINE intptr_t InternalGetExistingThreadLocal(intptr_t index) {
#define V8_FAST_TLS_SUPPORTED 1
V8_INLINE intptr_t InternalGetExistingThreadLocal(intptr_t index) {
extern V8_BASE_EXPORT intptr_t kMacTlsBaseOffset;
V8_INLINE intptr_t InternalGetExistingThreadLocal(intptr_t index);
inline intptr_t InternalGetExistingThreadLocal(intptr_t index) {
intptr_t result;
#if V8_HOST_ARCH_IA32
asm("movl %%gs:(,%1,4), %0;"
: "=r"(result) // Output must be a writable register.
: "r"(index));
asm("movl %%gs:(%1,%2,4), %0;"
:"=r"(result) // Output must be a writable register.
:"r"(kMacTlsBaseOffset), "r"(index));
#else
asm("movq %%gs:(,%1,8), %0;" : "=r"(result) : "r"(index));
asm("movq %%gs:(%1,%2,8), %0;"
:"=r"(result)
:"r"(kMacTlsBaseOffset), "r"(index));
#endif
return result;
}