[libc-commits] [libc] [libc] rework mutex (PR #92168)
Schrodinger ZHU Yifan via libc-commits
libc-commits at lists.llvm.org
Tue May 14 15:42:15 PDT 2024
https://github.com/SchrodingerZhu updated https://github.com/llvm/llvm-project/pull/92168
>From f543f61b615377aade605bbc8852646abdf01e7a Mon Sep 17 00:00:00 2001
From: Schrodinger ZHU Yifan <yifanzhu at rochester.edu>
Date: Tue, 14 May 2024 15:52:46 -0400
Subject: [PATCH 1/7] [libc] rework mutex
---
libc/config/config.json | 10 ++
libc/docs/configure.rst | 3 +
libc/hdr/types/CMakeLists.txt | 9 ++
libc/hdr/types/pid_t.h | 22 +++
libc/src/__support/File/dir.h | 2 +-
libc/src/__support/File/file.h | 2 +-
libc/src/__support/threads/fork_callbacks.cpp | 3 +-
libc/src/__support/threads/gpu/mutex.h | 2 +-
.../__support/threads/linux/CMakeLists.txt | 23 +++
libc/src/__support/threads/linux/mutex.h | 133 +++++++-----------
libc/src/__support/threads/linux/raw_mutex.h | 116 +++++++++++++++
libc/src/__support/threads/thread.cpp | 4 +-
libc/src/pthread/pthread_mutex_init.cpp | 5 +-
libc/src/pthread/pthread_mutexattr.h | 5 +
libc/src/stdlib/atexit.cpp | 2 +-
libc/src/threads/linux/CMakeLists.txt | 1 +
libc/src/threads/linux/CndVar.h | 30 ++--
libc/src/threads/mtx_init.cpp | 3 +-
.../__support/threads/thread_detach_test.cpp | 2 +-
19 files changed, 268 insertions(+), 109 deletions(-)
create mode 100644 libc/hdr/types/pid_t.h
create mode 100644 libc/src/__support/threads/linux/raw_mutex.h
diff --git a/libc/config/config.json b/libc/config/config.json
index d6ef891b9f260..ee51ed03cdace 100644
--- a/libc/config/config.json
+++ b/libc/config/config.json
@@ -40,5 +40,15 @@
"value": true,
"doc": "Enable -fstack-protector-strong to defend against stack smashing attack."
}
+ },
+ "pthread": {
+ "LIBC_CONF_TIMEOUT_ENSURE_MONOTONICITY": {
+ "value": true,
+ "doc": "Automatically adjust timeout to CLOCK_MONOTONIC."
+ },
+ "LIBC_CONF_RAW_MUTEX_DEFAULT_SPIN_COUNT": {
+ "value": 100,
+ "doc": "Default number of spins before blocking if a mutex is contented."
+ }
}
}
diff --git a/libc/docs/configure.rst b/libc/docs/configure.rst
index 8f8c44caa1153..34ceadb071991 100644
--- a/libc/docs/configure.rst
+++ b/libc/docs/configure.rst
@@ -34,6 +34,9 @@ to learn about the defaults for your platform and target.
- ``LIBC_CONF_PRINTF_DISABLE_INDEX_MODE``: Disable index mode in the printf format string.
- ``LIBC_CONF_PRINTF_DISABLE_WRITE_INT``: Disable handling of %n in printf format string.
- ``LIBC_CONF_PRINTF_FLOAT_TO_STR_USE_MEGA_LONG_DOUBLE_TABLE``: Use large table for better printf long double performance.
+* **"pthread" options**
+ - ``LIBC_CONF_RAW_MUTEX_DEFAULT_SPIN_COUNT``: Default number of spins before blocking if a mutex is contented.
+ - ``LIBC_CONF_TIMEOUT_ENSURE_MONOTONICITY``: Automatically adjust timeout to CLOCK_MONOTONIC.
* **"string" options**
- ``LIBC_CONF_MEMSET_X86_USE_SOFTWARE_PREFETCHING``: Inserts prefetch for write instructions (PREFETCHW) for memset on x86 to recover performance when hardware prefetcher is disabled.
- ``LIBC_CONF_STRING_UNSAFE_WIDE_READ``: Read more than a byte at a time to perform byte-string operations like strlen.
diff --git a/libc/hdr/types/CMakeLists.txt b/libc/hdr/types/CMakeLists.txt
index 3a1bb2f3c340f..8e87642f66088 100644
--- a/libc/hdr/types/CMakeLists.txt
+++ b/libc/hdr/types/CMakeLists.txt
@@ -108,3 +108,12 @@ add_proxy_header_library(
libc.include.llvm-libc-types.struct_timeval
libc.include.sys_time
)
+
+add_proxy_header_library(
+ pid_t
+ HDRS
+ pid_t.h
+ FULL_BUILD_DEPENDS
+ libc.include.llvm-libc-types.pid_t
+ libc.include.sys_types
+)
diff --git a/libc/hdr/types/pid_t.h b/libc/hdr/types/pid_t.h
new file mode 100644
index 0000000000000..34306fc4118cf
--- /dev/null
+++ b/libc/hdr/types/pid_t.h
@@ -0,0 +1,22 @@
+//===-- Proxy for pid_t ---------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIBC_HDR_TYPES_PID_T_H
+#define LLVM_LIBC_HDR_TYPES_PID_T_H
+
+#ifdef LIBC_FULL_BUILD
+
+#include "include/llvm-libc-types/pid_t.h"
+
+#else // Overlay mode
+
+#include <sys/types.h>
+
+#endif // LLVM_LIBC_FULL_BUILD
+
+#endif // LLVM_LIBC_HDR_TYPES_PID_T_H
diff --git a/libc/src/__support/File/dir.h b/libc/src/__support/File/dir.h
index a2f50f88e0e8b..ab445b6c0bec5 100644
--- a/libc/src/__support/File/dir.h
+++ b/libc/src/__support/File/dir.h
@@ -54,7 +54,7 @@ class Dir {
Dir(const Dir &) = delete;
explicit Dir(int fdesc)
- : fd(fdesc), readptr(0), fillsize(0), mutex(false, false, false) {}
+ : fd(fdesc), readptr(0), fillsize(0), mutex(false, false, false, false) {}
~Dir() = default;
Dir &operator=(const Dir &) = delete;
diff --git a/libc/src/__support/File/file.h b/libc/src/__support/File/file.h
index eafd3ab7d9107..6b41056cf40bd 100644
--- a/libc/src/__support/File/file.h
+++ b/libc/src/__support/File/file.h
@@ -154,7 +154,7 @@ class File {
uint8_t *buffer, size_t buffer_size, int buffer_mode,
bool owned, ModeFlags modeflags)
: platform_write(wf), platform_read(rf), platform_seek(sf),
- platform_close(cf), mutex(false, false, false), ungetc_buf(0),
+ platform_close(cf), mutex(false, false, false, false), ungetc_buf(0),
buf(buffer), bufsize(buffer_size), bufmode(buffer_mode), own_buf(owned),
mode(modeflags), pos(0), prev_op(FileOp::NONE), read_limit(0),
eof(false), err(false) {
diff --git a/libc/src/__support/threads/fork_callbacks.cpp b/libc/src/__support/threads/fork_callbacks.cpp
index 6efaf62f135ae..9ad3f38892f8f 100644
--- a/libc/src/__support/threads/fork_callbacks.cpp
+++ b/libc/src/__support/threads/fork_callbacks.cpp
@@ -33,7 +33,8 @@ class AtForkCallbackManager {
size_t next_index;
public:
- constexpr AtForkCallbackManager() : mtx(false, false, false), next_index(0) {}
+ constexpr AtForkCallbackManager()
+ : mtx(false, false, false, false), next_index(0) {}
bool register_triple(const ForkCallbackTriple &triple) {
cpp::lock_guard lock(mtx);
diff --git a/libc/src/__support/threads/gpu/mutex.h b/libc/src/__support/threads/gpu/mutex.h
index 71d0ef04cbfe5..9554083679335 100644
--- a/libc/src/__support/threads/gpu/mutex.h
+++ b/libc/src/__support/threads/gpu/mutex.h
@@ -19,7 +19,7 @@ namespace LIBC_NAMESPACE {
/// define the Mutex interface and require that only a single thread executes
/// code requiring a mutex lock.
struct Mutex {
- LIBC_INLINE constexpr Mutex(bool, bool, bool) {}
+ LIBC_INLINE constexpr Mutex(bool, bool, bool, bool) {}
LIBC_INLINE MutexError lock() { return MutexError::NONE; }
LIBC_INLINE MutexError unlock() { return MutexError::NONE; }
diff --git a/libc/src/__support/threads/linux/CMakeLists.txt b/libc/src/__support/threads/linux/CMakeLists.txt
index d3353f6b3ff8c..c207596e5072d 100644
--- a/libc/src/__support/threads/linux/CMakeLists.txt
+++ b/libc/src/__support/threads/linux/CMakeLists.txt
@@ -22,12 +22,35 @@ add_header_library(
libc.src.__support.time.linux.abs_timeout
)
+set(raw_mutex_additional_flags)
+if (LIBC_CONF_TIMEOUT_ENSURE_MONOTONICITY)
+ set(raw_mutex_additional_flags -DLIBC_COPT_TIMEOUT_ENSURE_MONOTONICITY)
+endif()
+
+add_header_library(
+ raw_mutex
+ HDRS
+ mutex.h
+ DEPENDS
+ .futex_utils
+ libc.src.__support.threads.sleep
+ libc.src.__support.time.linux.abs_timeout
+ libc.src.__support.time.linux.monotonicity
+ libc.src.__support.CPP.optional
+ libc.hdr.types.pid_t
+ COMPILE_OPTIONS
+ -DLIBC_COPT_RAW_MUTEX_DEFAULT_SPIN_COUNT=${LIBC_CONF_RAW_MUTEX_DEFAULT_SPIN_COUNT}
+ ${raw_mutex_additional_flags}
+
+)
+
add_header_library(
mutex
HDRS
mutex.h
DEPENDS
.futex_utils
+ .raw_mutex
libc.src.__support.threads.mutex_common
)
diff --git a/libc/src/__support/threads/linux/mutex.h b/libc/src/__support/threads/linux/mutex.h
index 6702de4651686..915919cba37e6 100644
--- a/libc/src/__support/threads/linux/mutex.h
+++ b/libc/src/__support/threads/linux/mutex.h
@@ -9,114 +9,81 @@
#ifndef LLVM_LIBC_SRC___SUPPORT_THREADS_LINUX_MUTEX_H
#define LLVM_LIBC_SRC___SUPPORT_THREADS_LINUX_MUTEX_H
+#include "hdr/types/pid_t.h"
+#include "src/__support/CPP/optional.h"
#include "src/__support/threads/linux/futex_utils.h"
+#include "src/__support/threads/linux/raw_mutex.h"
#include "src/__support/threads/mutex_common.h"
namespace LIBC_NAMESPACE {
-struct Mutex {
- unsigned char timed;
+
+// TODO: support shared/recursive/robust mutexes.
+class Mutex final : private internal::RawMutex {
+ // reserved timed, may be useful when combined with other flags.
+ [[maybe_unused]] unsigned char timed;
unsigned char recursive;
unsigned char robust;
+ unsigned char pshared;
- void *owner;
+ // TLS address may not work across forked processes. Use thead id instead.
+ pid_t owner;
unsigned long long lock_count;
- Futex futex_word;
-
enum class LockState : FutexWordType {
- Free,
- Locked,
- Waiting,
+ Free = UNLOCKED,
+ Locked = LOCKED,
+ Waiting = CONTENTED,
};
public:
- constexpr Mutex(bool istimed, bool isrecursive, bool isrobust)
- : timed(istimed), recursive(isrecursive), robust(isrobust),
- owner(nullptr), lock_count(0),
- futex_word(FutexWordType(LockState::Free)) {}
-
- static MutexError init(Mutex *mutex, bool istimed, bool isrecur,
- bool isrobust) {
- mutex->timed = istimed;
+ LIBC_INLINE constexpr Mutex(bool is_timed, bool is_recursive, bool is_robust,
+ bool is_pshared)
+ : internal::RawMutex(), timed(is_timed), recursive(is_recursive),
+ robust(is_robust), pshared(is_pshared), owner(0), lock_count(0) {}
+
+ LIBC_INLINE static MutexError init(Mutex *mutex, bool is_timed, bool isrecur,
+ bool isrobust, bool is_pshared) {
+ internal::RawMutex::init(mutex);
+ mutex->timed = is_timed;
mutex->recursive = isrecur;
mutex->robust = isrobust;
- mutex->owner = nullptr;
+ mutex->pshared = is_pshared;
+ mutex->owner = 0;
mutex->lock_count = 0;
- mutex->futex_word.set(FutexWordType(LockState::Free));
return MutexError::NONE;
}
- static MutexError destroy(Mutex *) { return MutexError::NONE; }
-
- MutexError reset();
-
- MutexError lock() {
- bool was_waiting = false;
- while (true) {
- FutexWordType mutex_status = FutexWordType(LockState::Free);
- FutexWordType locked_status = FutexWordType(LockState::Locked);
+ LIBC_INLINE static MutexError destroy(Mutex *) { return MutexError::NONE; }
- if (futex_word.compare_exchange_strong(
- mutex_status, FutexWordType(LockState::Locked))) {
- if (was_waiting)
- futex_word = FutexWordType(LockState::Waiting);
- return MutexError::NONE;
- }
-
- switch (LockState(mutex_status)) {
- case LockState::Waiting:
- // If other threads are waiting already, then join them. Note that the
- // futex syscall will block if the futex data is still
- // `LockState::Waiting` (the 4th argument to the syscall function
- // below.)
- futex_word.wait(FutexWordType(LockState::Waiting));
- was_waiting = true;
- // Once woken up/unblocked, try everything all over.
- continue;
- case LockState::Locked:
- // Mutex has been locked by another thread so set the status to
- // LockState::Waiting.
- if (futex_word.compare_exchange_strong(
- locked_status, FutexWordType(LockState::Waiting))) {
- // If we are able to set the futex data to `LockState::Waiting`, then
- // we will wait for the futex to be woken up. Note again that the
- // following syscall will block only if the futex data is still
- // `LockState::Waiting`.
- futex_word.wait(FutexWordType(LockState::Waiting));
- was_waiting = true;
- }
- continue;
- case LockState::Free:
- // If it was LockState::Free, we shouldn't be here at all.
- return MutexError::BAD_LOCK_STATE;
- }
- }
+ LIBC_INLINE MutexError lock() {
+ this->internal::RawMutex::lock(
+ /* timeout */ cpp::nullopt,
+ /* is_pshared */ this->pshared,
+ /* spin_count */ LIBC_COPT_RAW_MUTEX_DEFAULT_SPIN_COUNT);
+ // TODO: record owner and lock count.
+ return MutexError::NONE;
}
- MutexError unlock() {
- while (true) {
- FutexWordType mutex_status = FutexWordType(LockState::Waiting);
- if (futex_word.compare_exchange_strong(mutex_status,
- FutexWordType(LockState::Free))) {
- // If any thread is waiting to be woken up, then do it.
- futex_word.notify_one();
- return MutexError::NONE;
- }
+ LIBC_INLINE MutexError timed_lock(internal::AbsTimeout abs_time) {
+ if (this->internal::RawMutex::lock(
+ abs_time, /* is_shared */ this->pshared,
+ /* spin_count */ LIBC_COPT_RAW_MUTEX_DEFAULT_SPIN_COUNT))
+ return MutexError::NONE;
+ return MutexError::TIMEOUT;
+ }
- if (mutex_status == FutexWordType(LockState::Locked)) {
- // If nobody was waiting at this point, just free it.
- if (futex_word.compare_exchange_strong(mutex_status,
- FutexWordType(LockState::Free)))
- return MutexError::NONE;
- } else {
- // This can happen, for example if some thread tries to unlock an
- // already free mutex.
- return MutexError::UNLOCK_WITHOUT_LOCK;
- }
- }
+ LIBC_INLINE MutexError unlock() {
+ if (this->internal::RawMutex::unlock(/* is_shared */ this->pshared))
+ return MutexError::NONE;
+ return MutexError::UNLOCK_WITHOUT_LOCK;
}
- MutexError trylock();
+ LIBC_INLINE MutexError try_lock() {
+ if (this->internal::RawMutex::try_lock())
+ return MutexError::NONE;
+ return MutexError::BUSY;
+ }
+ friend struct CndVar;
};
} // namespace LIBC_NAMESPACE
diff --git a/libc/src/__support/threads/linux/raw_mutex.h b/libc/src/__support/threads/linux/raw_mutex.h
new file mode 100644
index 0000000000000..93da725d66d61
--- /dev/null
+++ b/libc/src/__support/threads/linux/raw_mutex.h
@@ -0,0 +1,116 @@
+//===--- Implementation of a Linux RawMutex class ---------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+#ifndef LLVM_LIBC_SRC___SUPPORT_THREADS_LINUX_RAW_MUTEX_H
+#define LLVM_LIBC_SRC___SUPPORT_THREADS_LINUX_RAW_MUTEX_H
+
+#include "futex_word.h"
+#include "src/__support/CPP/optional.h"
+#include "src/__support/common.h"
+#include "src/__support/macros/attributes.h"
+#include "src/__support/threads/linux/futex_utils.h"
+#include "src/__support/threads/sleep.h"
+#include "src/__support/time/linux/abs_timeout.h"
+#ifdef LIBC_COPT_TIMEOUT_ENSURE_MONOTONICITY
+#include "src/__support/time/linux/monotonicity.h"
+#endif
+
+#ifndef LIBC_COPT_RAW_MUTEX_DEFAULT_SPIN_COUNT
+#define LIBC_COPT_RAW_MUTEX_DEFAULT_SPIN_COUNT 100
+#endif
+
+namespace LIBC_NAMESPACE {
+namespace internal {
+// Lock is a simple timable lock for internal usage.
+// This is separated from Mutex because this one does not need to consider
+// rubustness and reentrancy. Also, this one has spin optimization for shorter
+// critical sections.
+class RawMutex {
+protected:
+ Futex futex;
+ LIBC_INLINE_VAR static constexpr FutexWordType UNLOCKED = 0b00;
+ LIBC_INLINE_VAR static constexpr FutexWordType LOCKED = 0b01;
+ LIBC_INLINE_VAR static constexpr FutexWordType CONTENTED = 0b10;
+
+ LIBC_INLINE FutexWordType spin(uint_fast32_t spin_count) {
+ FutexWordType result;
+ for (;;) {
+ result = futex.load(cpp::MemoryOrder::RELAXED);
+ // spin until one of the following conditions is met:
+ // - the mutex is unlocked
+ // - the mutex is contented
+ // - the spin count reaches 0
+ if (result != LOCKED || spin_count == 0)
+ return result;
+ // Pause the pipeline to avoid extraneous memory operations due to
+ // speculation.
+ sleep_briefly();
+ spin_count--;
+ };
+ }
+
+ // Return true if the lock is acquired. Return false if timeout happens before
+ // the lock is acquired.
+ [[gnu::cold]] LIBC_INLINE bool
+ lock_contented(cpp::optional<Futex::Timeout> timeout, bool is_pshared,
+ uint_fast32_t spin_count) {
+ FutexWordType state = spin(spin_count);
+ // Before go into contention state, try to grab the lock.
+ if (state == UNLOCKED &&
+ futex.compare_exchange_strong(state, LOCKED, cpp::MemoryOrder::ACQUIRE,
+ cpp::MemoryOrder::RELAXED))
+ return true;
+#ifdef LIBC_COPT_TIMEOUT_ENSURE_MONOTONICITY
+ if (timeout)
+ ensure_monotonicity(*timeout);
+#endif
+ for (;;) {
+ // Try to grab the lock if it is unlocked. Mark contented if it is locked.
+ if (state != CONTENTED &&
+ futex.exchange(CONTENTED, cpp::MemoryOrder::ACQUIRE) == UNLOCKED)
+ return true;
+ // Contention persists. Park the thread and wait for further notification.
+ if (-ETIMEDOUT == futex.wait(CONTENTED, timeout, is_pshared))
+ return false;
+ // Continue to spin after waking up.
+ state = spin(spin_count);
+ }
+ }
+
+ [[gnu::cold]] LIBC_INLINE void wake(bool is_pshared) {
+ futex.notify_one(is_pshared);
+ }
+
+public:
+ LIBC_INLINE static void init(RawMutex *mutex) { mutex->futex = UNLOCKED; }
+ LIBC_INLINE constexpr RawMutex() : futex(UNLOCKED) {}
+ LIBC_INLINE bool try_lock() {
+ FutexWordType expected = UNLOCKED;
+ // Use strong version since this is a one-time operation.
+ return futex.compare_exchange_strong(
+ expected, LOCKED, cpp::MemoryOrder::ACQUIRE, cpp::MemoryOrder::RELAXED);
+ }
+ LIBC_INLINE bool
+ lock(cpp::optional<Futex::Timeout> timeout = cpp::nullopt,
+ bool is_shared = false,
+ uint_fast32_t spin_count = LIBC_COPT_RAW_MUTEX_DEFAULT_SPIN_COUNT) {
+ // Timeout will not be checked if immediate lock is possible.
+ return try_lock() || lock_contented(timeout, is_shared, spin_count);
+ }
+ LIBC_INLINE bool unlock(bool is_pshared = false) {
+ FutexWordType prev = futex.exchange(UNLOCKED, cpp::MemoryOrder::RELEASE);
+ // if there is someone waiting, wake them up
+ if (prev == CONTENTED)
+ wake(is_pshared);
+ // Detect invalid unlock operation.
+ return prev == LOCKED;
+ }
+};
+} // namespace internal
+} // namespace LIBC_NAMESPACE
+
+#endif // LLVM_LIBC_SRC___SUPPORT_THREADS_LINUX_RAW_MUTEX_H
diff --git a/libc/src/__support/threads/thread.cpp b/libc/src/__support/threads/thread.cpp
index 7b02f8246e24b..2bea01bf332b3 100644
--- a/libc/src/__support/threads/thread.cpp
+++ b/libc/src/__support/threads/thread.cpp
@@ -54,7 +54,7 @@ class TSSKeyMgr {
cpp::array<TSSKeyUnit, TSS_KEY_COUNT> units;
public:
- constexpr TSSKeyMgr() : mtx(false, false, false) {}
+ constexpr TSSKeyMgr() : mtx(false, false, false, false) {}
cpp::optional<unsigned int> new_key(TSSDtor *dtor) {
cpp::lock_guard lock(mtx);
@@ -111,7 +111,7 @@ class ThreadAtExitCallbackMgr {
FixedVector<AtExitUnit, 1024> callback_list;
public:
- constexpr ThreadAtExitCallbackMgr() : mtx(false, false, false) {}
+ constexpr ThreadAtExitCallbackMgr() : mtx(false, false, false, false) {}
int add_callback(AtExitCallback *callback, void *obj) {
cpp::lock_guard lock(mtx);
diff --git a/libc/src/pthread/pthread_mutex_init.cpp b/libc/src/pthread/pthread_mutex_init.cpp
index f64d1fe68ad20..35615c449c044 100644
--- a/libc/src/pthread/pthread_mutex_init.cpp
+++ b/libc/src/pthread/pthread_mutex_init.cpp
@@ -26,9 +26,10 @@ LLVM_LIBC_FUNCTION(int, pthread_mutex_init,
const pthread_mutexattr_t *__restrict attr)) {
auto mutexattr = attr == nullptr ? DEFAULT_MUTEXATTR : *attr;
auto err =
- Mutex::init(reinterpret_cast<Mutex *>(m), false,
+ Mutex::init(reinterpret_cast<Mutex *>(m), /* timeout is supported */ true,
get_mutexattr_type(mutexattr) & PTHREAD_MUTEX_RECURSIVE,
- get_mutexattr_robust(mutexattr) & PTHREAD_MUTEX_ROBUST);
+ get_mutexattr_robust(mutexattr) & PTHREAD_MUTEX_ROBUST,
+ get_mutexattr_pshared(mutexattr) & PTHREAD_PROCESS_SHARED);
return err == MutexError::NONE ? 0 : EAGAIN;
}
diff --git a/libc/src/pthread/pthread_mutexattr.h b/libc/src/pthread/pthread_mutexattr.h
index 8b435854416a7..292ceebe049f9 100644
--- a/libc/src/pthread/pthread_mutexattr.h
+++ b/libc/src/pthread/pthread_mutexattr.h
@@ -43,6 +43,11 @@ LIBC_INLINE int get_mutexattr_robust(pthread_mutexattr_t attr) {
unsigned(PThreadMutexAttrPos::ROBUST_SHIFT);
}
+LIBC_INLINE int get_mutexattr_pshared(pthread_mutexattr_t attr) {
+ return (attr & unsigned(PThreadMutexAttrPos::PSHARED_MASK)) >>
+ unsigned(PThreadMutexAttrPos::PSHARED_SHIFT);
+}
+
} // namespace LIBC_NAMESPACE
#endif // LLVM_LIBC_SRC_PTHREAD_PTHREAD_MUTEXATTR_H
diff --git a/libc/src/stdlib/atexit.cpp b/libc/src/stdlib/atexit.cpp
index 4f0497444773d..fd24811000123 100644
--- a/libc/src/stdlib/atexit.cpp
+++ b/libc/src/stdlib/atexit.cpp
@@ -17,7 +17,7 @@ namespace LIBC_NAMESPACE {
namespace {
-Mutex handler_list_mtx(false, false, false);
+Mutex handler_list_mtx(false, false, false, false);
using AtExitCallback = void(void *);
using StdCAtExitCallback = void(void);
diff --git a/libc/src/threads/linux/CMakeLists.txt b/libc/src/threads/linux/CMakeLists.txt
index 68b7106c2052f..be0485def839d 100644
--- a/libc/src/threads/linux/CMakeLists.txt
+++ b/libc/src/threads/linux/CMakeLists.txt
@@ -10,6 +10,7 @@ add_header_library(
libc.src.__support.CPP.mutex
libc.src.__support.OSUtil.osutil
libc.src.__support.threads.mutex
+ libc.src.__support.threads.linux.raw_mutex
libc.src.__support.threads.linux.futex_utils
)
diff --git a/libc/src/threads/linux/CndVar.h b/libc/src/threads/linux/CndVar.h
index c08ffa393856f..c9a49b005eb96 100644
--- a/libc/src/threads/linux/CndVar.h
+++ b/libc/src/threads/linux/CndVar.h
@@ -14,6 +14,7 @@
#include "src/__support/CPP/optional.h"
#include "src/__support/OSUtil/syscall.h" // For syscall functions.
#include "src/__support/threads/linux/futex_utils.h"
+#include "src/__support/threads/linux/raw_mutex.h"
#include "src/__support/threads/mutex.h"
#include <linux/futex.h> // For futex operations.
@@ -23,7 +24,7 @@
namespace LIBC_NAMESPACE {
-struct CndVar {
+struct CndVar final : private internal::RawMutex {
enum CndWaiterStatus : uint32_t {
WS_Waiting = 0xE,
WS_Signalled = 0x5,
@@ -36,19 +37,18 @@ struct CndVar {
CndWaiter *waitq_front;
CndWaiter *waitq_back;
- Mutex qmtx;
- static int init(CndVar *cv) {
+ LIBC_INLINE static int init(CndVar *cv) {
cv->waitq_front = cv->waitq_back = nullptr;
- auto err = Mutex::init(&cv->qmtx, false, false, false);
- return err == MutexError::NONE ? thrd_success : thrd_error;
+ internal::RawMutex::init(cv);
+ return thrd_success;
}
- static void destroy(CndVar *cv) {
+ LIBC_INLINE static void destroy(CndVar *cv) {
cv->waitq_front = cv->waitq_back = nullptr;
}
- int wait(Mutex *m) {
+ LIBC_INLINE int wait(Mutex *m) {
// The goal is to perform "unlock |m| and wait" in an
// atomic operation. However, it is not possible to do it
// in the true sense so we do it in spirit. Before unlocking
@@ -60,7 +60,7 @@ struct CndVar {
CndWaiter waiter;
{
- cpp::lock_guard ml(qmtx);
+ cpp::lock_guard ml(static_cast<internal::RawMutex &>(*this));
CndWaiter *old_back = nullptr;
if (waitq_front == nullptr) {
waitq_front = waitq_back = &waiter;
@@ -94,12 +94,12 @@ struct CndVar {
return err == MutexError::NONE ? thrd_success : thrd_error;
}
- int notify_one() {
+ LIBC_INLINE int notify_one() {
// We don't use an RAII locker in this method as we want to unlock
// |qmtx| and signal the waiter using a single FUTEX_WAKE_OP signal.
- qmtx.lock();
+ this->lock();
if (waitq_front == nullptr) {
- qmtx.unlock();
+ this->unlock();
return thrd_success;
}
@@ -108,18 +108,18 @@ struct CndVar {
if (waitq_front == nullptr)
waitq_back = nullptr;
- qmtx.futex_word = FutexWordType(Mutex::LockState::Free);
+ this->futex = FutexWordType(Mutex::LockState::Free);
// this is a special WAKE_OP, so we use syscall directly
LIBC_NAMESPACE::syscall_impl<long>(
- FUTEX_SYSCALL_ID, &qmtx.futex_word.val, FUTEX_WAKE_OP, 1, 1,
+ FUTEX_SYSCALL_ID, &this->futex.val, FUTEX_WAKE_OP, 1, 1,
&first->futex_word.val,
FUTEX_OP(FUTEX_OP_SET, WS_Signalled, FUTEX_OP_CMP_EQ, WS_Waiting));
return thrd_success;
}
- int broadcast() {
- cpp::lock_guard ml(qmtx);
+ LIBC_INLINE int broadcast() {
+ cpp::lock_guard ml(static_cast<internal::RawMutex &>(*this));
uint32_t dummy_futex_word;
CndWaiter *waiter = waitq_front;
waitq_front = waitq_back = nullptr;
diff --git a/libc/src/threads/mtx_init.cpp b/libc/src/threads/mtx_init.cpp
index 74d08d33b116b..7cd848d12ee6d 100644
--- a/libc/src/threads/mtx_init.cpp
+++ b/libc/src/threads/mtx_init.cpp
@@ -20,7 +20,8 @@ static_assert(sizeof(Mutex) <= sizeof(mtx_t),
LLVM_LIBC_FUNCTION(int, mtx_init, (mtx_t * m, int type)) {
auto err = Mutex::init(reinterpret_cast<Mutex *>(m), type & mtx_timed,
- type & mtx_recursive, 0);
+ type & mtx_recursive, /* is_robust */ false,
+ /* is_pshared */ false);
return err == MutexError::NONE ? thrd_success : thrd_error;
}
diff --git a/libc/test/integration/src/__support/threads/thread_detach_test.cpp b/libc/test/integration/src/__support/threads/thread_detach_test.cpp
index 697d991d07547..b11e704551aab 100644
--- a/libc/test/integration/src/__support/threads/thread_detach_test.cpp
+++ b/libc/test/integration/src/__support/threads/thread_detach_test.cpp
@@ -10,7 +10,7 @@
#include "src/__support/threads/thread.h"
#include "test/IntegrationTest/test.h"
-LIBC_NAMESPACE::Mutex mutex(false, false, false);
+LIBC_NAMESPACE::Mutex mutex(false, false, false, false);
int func(void *) {
mutex.lock();
>From 066bfc4ba8a091387d96be3f643e59db55498dc6 Mon Sep 17 00:00:00 2001
From: Schrodinger ZHU Yifan <yifanzhu at rochester.edu>
Date: Tue, 14 May 2024 16:30:31 -0400
Subject: [PATCH 2/7] [libc] fix missing dep
---
libc/include/llvm-libc-types/CMakeLists.txt | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/libc/include/llvm-libc-types/CMakeLists.txt b/libc/include/llvm-libc-types/CMakeLists.txt
index 018b6c58316c3..9e9a2fabd5fa4 100644
--- a/libc/include/llvm-libc-types/CMakeLists.txt
+++ b/libc/include/llvm-libc-types/CMakeLists.txt
@@ -7,7 +7,7 @@ add_header(__call_once_func_t HDR __call_once_func_t.h)
add_header(__exec_argv_t HDR __exec_argv_t.h)
add_header(__exec_envp_t HDR __exec_envp_t.h)
add_header(__futex_word HDR __futex_word.h)
-add_header(__mutex_type HDR __mutex_type.h DEPENDS .__futex_word)
+add_header(__mutex_type HDR __mutex_type.h DEPENDS .__futex_word .pid_t)
add_header(__pthread_once_func_t HDR __pthread_once_func_t.h)
add_header(__pthread_start_t HDR __pthread_start_t.h)
add_header(__pthread_tss_dtor_t HDR __pthread_tss_dtor_t.h)
>From bd5667ba47a780e4e3ef454cdb67e0547c2af138 Mon Sep 17 00:00:00 2001
From: Schrodinger ZHU Yifan <yifanzhu at rochester.edu>
Date: Tue, 14 May 2024 16:34:17 -0400
Subject: [PATCH 3/7] [libc] adjust fields
---
libc/include/llvm-libc-types/CMakeLists.txt | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/libc/include/llvm-libc-types/CMakeLists.txt b/libc/include/llvm-libc-types/CMakeLists.txt
index 9e9a2fabd5fa4..8ac7be391fb2e 100644
--- a/libc/include/llvm-libc-types/CMakeLists.txt
+++ b/libc/include/llvm-libc-types/CMakeLists.txt
@@ -7,6 +7,7 @@ add_header(__call_once_func_t HDR __call_once_func_t.h)
add_header(__exec_argv_t HDR __exec_argv_t.h)
add_header(__exec_envp_t HDR __exec_envp_t.h)
add_header(__futex_word HDR __futex_word.h)
+add_header(pid_t HDR pid_t.h)
add_header(__mutex_type HDR __mutex_type.h DEPENDS .__futex_word .pid_t)
add_header(__pthread_once_func_t HDR __pthread_once_func_t.h)
add_header(__pthread_start_t HDR __pthread_start_t.h)
@@ -45,7 +46,6 @@ add_header(mtx_t HDR mtx_t.h DEPENDS .__futex_word .__mutex_type)
add_header(nlink_t HDR nlink_t.h)
add_header(off_t HDR off_t.h)
add_header(once_flag HDR once_flag.h DEPENDS .__futex_word)
-add_header(pid_t HDR pid_t.h)
add_header(posix_spawn_file_actions_t HDR posix_spawn_file_actions_t.h)
add_header(posix_spawnattr_t HDR posix_spawnattr_t.h)
add_header(pthread_attr_t HDR pthread_attr_t.h DEPENDS .size_t)
>From b3cb18b1f2381bdb4ede3a64406ad88bb3ed18bb Mon Sep 17 00:00:00 2001
From: Schrodinger ZHU Yifan <yifanzhu at rochester.edu>
Date: Tue, 14 May 2024 16:34:53 -0400
Subject: [PATCH 4/7] [libc] fix typo
---
libc/src/__support/threads/linux/mutex.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/libc/src/__support/threads/linux/mutex.h b/libc/src/__support/threads/linux/mutex.h
index 915919cba37e6..4a49d7c68b2e5 100644
--- a/libc/src/__support/threads/linux/mutex.h
+++ b/libc/src/__support/threads/linux/mutex.h
@@ -25,7 +25,7 @@ class Mutex final : private internal::RawMutex {
unsigned char robust;
unsigned char pshared;
- // TLS address may not work across forked processes. Use thead id instead.
+ // TLS address may not work across forked processes. Use thread id instead.
pid_t owner;
unsigned long long lock_count;
>From eb675fe67b289fed8926cbb2d27c0de1344cac4a Mon Sep 17 00:00:00 2001
From: Schrodinger ZHU Yifan <yifanzhu at rochester.edu>
Date: Tue, 14 May 2024 16:37:01 -0400
Subject: [PATCH 5/7] [libc] fix unlock detection
---
libc/src/__support/threads/linux/raw_mutex.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/libc/src/__support/threads/linux/raw_mutex.h b/libc/src/__support/threads/linux/raw_mutex.h
index 93da725d66d61..f2209f50cc458 100644
--- a/libc/src/__support/threads/linux/raw_mutex.h
+++ b/libc/src/__support/threads/linux/raw_mutex.h
@@ -107,7 +107,7 @@ class RawMutex {
if (prev == CONTENTED)
wake(is_pshared);
// Detect invalid unlock operation.
- return prev == LOCKED;
+ return prev != UNLOCKED;
}
};
} // namespace internal
>From 656b690a9260c7553838095bbda06b7684dae1cc Mon Sep 17 00:00:00 2001
From: Schrodinger ZHU Yifan <yifanzhu at rochester.edu>
Date: Tue, 14 May 2024 16:37:44 -0400
Subject: [PATCH 6/7] [libc] fix typo
---
libc/src/__support/threads/linux/raw_mutex.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/libc/src/__support/threads/linux/raw_mutex.h b/libc/src/__support/threads/linux/raw_mutex.h
index f2209f50cc458..778d036851af4 100644
--- a/libc/src/__support/threads/linux/raw_mutex.h
+++ b/libc/src/__support/threads/linux/raw_mutex.h
@@ -27,7 +27,7 @@ namespace LIBC_NAMESPACE {
namespace internal {
// Lock is a simple timable lock for internal usage.
// This is separated from Mutex because this one does not need to consider
-// rubustness and reentrancy. Also, this one has spin optimization for shorter
+// robustness and reentrancy. Also, this one has spin optimization for shorter
// critical sections.
class RawMutex {
protected:
>From 893835515c6bc5082944600a4134dd669a5fe441 Mon Sep 17 00:00:00 2001
From: Schrodinger ZHU Yifan <yifanzhu at rochester.edu>
Date: Tue, 14 May 2024 18:41:58 -0400
Subject: [PATCH 7/7] [libc] more cleanups
---
libc/src/__support/threads/linux/mutex.h | 9 +--------
libc/src/threads/linux/CndVar.h | 2 +-
2 files changed, 2 insertions(+), 9 deletions(-)
diff --git a/libc/src/__support/threads/linux/mutex.h b/libc/src/__support/threads/linux/mutex.h
index 4a49d7c68b2e5..ea43892820bc2 100644
--- a/libc/src/__support/threads/linux/mutex.h
+++ b/libc/src/__support/threads/linux/mutex.h
@@ -20,7 +20,7 @@ namespace LIBC_NAMESPACE {
// TODO: support shared/recursive/robust mutexes.
class Mutex final : private internal::RawMutex {
// reserved timed, may be useful when combined with other flags.
- [[maybe_unused]] unsigned char timed;
+ unsigned char timed;
unsigned char recursive;
unsigned char robust;
unsigned char pshared;
@@ -29,12 +29,6 @@ class Mutex final : private internal::RawMutex {
pid_t owner;
unsigned long long lock_count;
- enum class LockState : FutexWordType {
- Free = UNLOCKED,
- Locked = LOCKED,
- Waiting = CONTENTED,
- };
-
public:
LIBC_INLINE constexpr Mutex(bool is_timed, bool is_recursive, bool is_robust,
bool is_pshared)
@@ -83,7 +77,6 @@ class Mutex final : private internal::RawMutex {
return MutexError::NONE;
return MutexError::BUSY;
}
- friend struct CndVar;
};
} // namespace LIBC_NAMESPACE
diff --git a/libc/src/threads/linux/CndVar.h b/libc/src/threads/linux/CndVar.h
index c9a49b005eb96..7946bd0e9a128 100644
--- a/libc/src/threads/linux/CndVar.h
+++ b/libc/src/threads/linux/CndVar.h
@@ -108,7 +108,7 @@ struct CndVar final : private internal::RawMutex {
if (waitq_front == nullptr)
waitq_back = nullptr;
- this->futex = FutexWordType(Mutex::LockState::Free);
+ this->futex = internal::RawMutex::UNLOCKED;
// this is a special WAKE_OP, so we use syscall directly
LIBC_NAMESPACE::syscall_impl<long>(
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