Merge pull request 'libc: add common implementations of pthread_spin_*' (#31990) from GasInfinity/zig:pthread-spin into master

Reviewed-on: https://codeberg.org/ziglang/zig/pulls/31990
Reviewed-by: Andrew Kelley <andrew@ziglang.org>

lib/c.zig

@@ -68,6 +68,7 @@ comptime {
         _ = @import("c/malloc.zig");
     }
     _ = @import("c/math.zig");
+    _ = @import("c/pthread.zig");
     _ = @import("c/search.zig");
     _ = @import("c/stdlib.zig");
     _ = @import("c/string.zig");

lib/c/pthread.zig

@@ -0,0 +1,57 @@
+const builtin = @import("builtin");
+
+const std = @import("std");
+const c = std.c;
+
+const symbol = @import("../c.zig").symbol;
+
+comptime {
+    if (builtin.target.isMuslLibC() or builtin.target.isWasiLibC() or builtin.target.isMinGW()) {
+        symbol(&pthread_spin_init, "pthread_spin_init");
+        symbol(&pthread_spin_destroy, "pthread_spin_destroy");
+        symbol(&pthread_spin_trylock, "pthread_spin_trylock");
+        symbol(&pthread_spin_lock, "pthread_spin_lock");
+        symbol(&pthread_spin_unlock, "pthread_spin_unlock");
+    }
+}
+
+const SpinLock = enum(c.pthread_spinlock_t) {
+    unlocked = if (builtin.target.isMinGW()) -1 else 0,
+    locked = if (builtin.target.isMinGW()) 0 else @intFromEnum(c.E.BUSY),
+};
+
+fn pthread_spin_init(s: *c.pthread_spinlock_t, pshared: c_int) callconv(.c) c_int {
+    _ = pshared;
+    const spin: *SpinLock = @ptrCast(s);
+    spin.* = .unlocked;
+    return 0;
+}
+
+fn pthread_spin_destroy(s: *c.pthread_spinlock_t) callconv(.c) c_int {
+    const spin: *SpinLock = @ptrCast(s);
+    spin.* = undefined;
+    return 0;
+}
+
+fn pthread_spin_trylock(s: *c.pthread_spinlock_t) callconv(.c) c_int {
+    const spin: *SpinLock = @ptrCast(s);
+    return if (@cmpxchgStrong(SpinLock, spin, .unlocked, .locked, .acquire, .monotonic)) |_| @intFromEnum(c.E.BUSY) else 0;
+}
+
+fn pthread_spin_lock(s: *c.pthread_spinlock_t) callconv(.c) c_int {
+    const spin: *SpinLock = @ptrCast(s);
+    if (builtin.single_threaded and @atomicLoad(SpinLock, spin, .monotonic) == .locked) return @intFromEnum(c.E.DEADLK);
+
+    while (@cmpxchgWeak(SpinLock, spin, .unlocked, .locked, .acquire, .monotonic)) |_| {
+        std.atomic.spinLoopHint();
+    }
+    return 0;
+}
+
+fn pthread_spin_unlock(s: *c.pthread_spinlock_t) callconv(.c) c_int {
+    const spin: *SpinLock = @ptrCast(s);
+
+    // "The results are undefined if the lock is not held by the calling thread"
+    std.debug.assert(@atomicRmw(SpinLock, spin, .Xchg, .unlocked, .release) == .locked);
+    return 0;
+}

lib/libc/mingw/winpthreads/spinlock.c

@@ -1,82 +0,0 @@
-/*
-   Copyright (c) 2013 mingw-w64 project
-   Copyright (c) 2015 Intel Corporation
-
-   Permission is hereby granted, free of charge, to any person obtaining a
-   copy of this software and associated documentation files (the "Software"),
-   to deal in the Software without restriction, including without limitation
-   the rights to use, copy, modify, merge, publish, distribute, sublicense,
-   and/or sell copies of the Software, and to permit persons to whom the
-   Software is furnished to do so, subject to the following conditions:
-
-   The above copyright notice and this permission notice shall be included in
-   all copies or substantial portions of the Software.
-
-   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
-   IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
-   FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
-   AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
-   LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
-   FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
-   DEALINGS IN THE SOFTWARE.
-*/
-
-#ifdef HAVE_CONFIG_H
-#include "config.h"
-#endif
-
-#define WIN32_LEAN_AND_MEAN
-#include <windows.h>
-
-/* public header files */
-#include "pthread.h"
-/* internal header files */
-#include "misc.h"
-
-/* We use the pthread_spinlock_t itself as a lock:
-   -1 is free, 0 is locked.
-   (This is dictated by PTHREAD_SPINLOCK_INITIALIZER, which we can't change
-   without breaking binary compatibility.) */
-typedef intptr_t spinlock_word_t;
-
-int
-pthread_spin_init (pthread_spinlock_t *lock, int pshared)
-{
-  spinlock_word_t *lk = (spinlock_word_t *)lock;
-  *lk = -1;
-  return 0;
-}
-
-
-int
-pthread_spin_destroy (pthread_spinlock_t *lock)
-{
-  return 0;
-}
-
-int
-pthread_spin_lock (pthread_spinlock_t *lock)
-{
-  volatile spinlock_word_t *lk = (volatile spinlock_word_t *)lock;
-  while (unlikely(InterlockedExchangePointer((PVOID volatile *)lk, 0) == 0))
-    do {
-      YieldProcessor();
-    } while (*lk == 0);
-  return 0;
-}
-
-int
-pthread_spin_trylock (pthread_spinlock_t *lock)
-{
-  spinlock_word_t *lk = (spinlock_word_t *)lock;
-  return InterlockedExchangePointer((PVOID volatile *)lk, 0) == 0 ? EBUSY : 0;
-}
-
-
-int
-pthread_spin_unlock (pthread_spinlock_t *lock)
-{
-  volatile spinlock_word_t *lk = (volatile spinlock_word_t *)lock;
-  *lk = -1;
-  return 0;
-}

lib/libc/musl/src/thread/pthread_spin_destroy.c

@@ -1,6 +0,0 @@
-#include "pthread_impl.h"
-
-int pthread_spin_destroy(pthread_spinlock_t *s)
-{
-	return 0;
-}

lib/libc/musl/src/thread/pthread_spin_init.c

@@ -1,6 +0,0 @@
-#include "pthread_impl.h"
-
-int pthread_spin_init(pthread_spinlock_t *s, int shared)
-{
-	return *s = 0;
-}

lib/libc/musl/src/thread/pthread_spin_lock.c

@@ -1,8 +0,0 @@
-#include "pthread_impl.h"
-#include <errno.h>
-
-int pthread_spin_lock(pthread_spinlock_t *s)
-{
-	while (*(volatile int *)s || a_cas(s, 0, EBUSY)) a_spin();
-	return 0;
-}

lib/libc/musl/src/thread/pthread_spin_trylock.c

@@ -1,7 +0,0 @@
-#include "pthread_impl.h"
-#include <errno.h>
-
-int pthread_spin_trylock(pthread_spinlock_t *s)
-{
-	return a_cas(s, 0, EBUSY);
-}

lib/libc/musl/src/thread/pthread_spin_unlock.c

@@ -1,7 +0,0 @@
-#include "pthread_impl.h"
-
-int pthread_spin_unlock(pthread_spinlock_t *s)
-{
-	a_store(s, 0);
-	return 0;
-}

lib/libc/wasi/thread-stub/pthread_spin_lock.c

@@ -1,8 +0,0 @@
-#include "pthread_impl.h"
-
-int pthread_spin_lock(pthread_spinlock_t *s)
-{
-	if (*s) return EDEADLK;
-	*s = 1;
-	return 0;
-}

lib/libc/wasi/thread-stub/pthread_spin_trylock.c

@@ -1,8 +0,0 @@
-#include "pthread_impl.h"
-
-int pthread_spin_trylock(pthread_spinlock_t *s)
-{
-	if (*s) return EBUSY;
-	*s = 1;
-	return 0;
-}

lib/libc/wasi/thread-stub/pthread_spin_unlock.c

@@ -1,7 +0,0 @@
-#include "pthread_impl.h"
-
-int pthread_spin_unlock(pthread_spinlock_t *s)
-{
-	*s = 0;
-	return 0;
-}

lib/std/c.zig

@@ -7898,6 +7898,20 @@ pub const Stat = switch (native_os) {
     else => void,
 };
 
+pub const pthread_spinlock_t = switch (native_os) {
+    .openbsd => openbsd.pthread_spinlock_t,
+    .freebsd => extern struct {
+        inner: ?*anyopaque = null,
+    },
+    .netbsd => extern struct {
+        pts_magic: c_uint,
+        spin: pthread_spin_t,
+        pts_flags: c_int,
+    },
+    .windows => isize,
+    else => c_int,
+};
+
 pub const pthread_mutex_t = switch (native_os) {
     .linux => extern struct {
         data: [data_len]u8 align(@alignOf(usize)) = [_]u8{0} ** data_len,
@@ -10956,6 +10970,19 @@ pub extern "c" fn dn_expand(
     length: c_int,
 ) c_int;
 
+pub const PTHREAD_PROCESS_PRIVATE: c_int = if (native_os.isDarwin())
+    2
+else
+    0;
+
+pub const PTHREAD_PROCESS_SHARED: c_int = 1;
+
+pub extern "c" fn pthread_spin_init(spin: *pthread_spinlock_t, pshared: c_int) c_int;
+pub extern "c" fn pthread_spin_lock(spin: *pthread_spinlock_t) c_int;
+pub extern "c" fn pthread_spin_unlock(spin: *pthread_spinlock_t) c_int;
+pub extern "c" fn pthread_spin_trylock(spin: *pthread_spinlock_t) c_int;
+pub extern "c" fn pthread_spin_destroy(spin: *pthread_spinlock_t) c_int;
+
 pub const PTHREAD_MUTEX_INITIALIZER: pthread_mutex_t = .{};
 pub extern "c" fn pthread_mutex_lock(mutex: *pthread_mutex_t) E;
 pub extern "c" fn pthread_mutex_unlock(mutex: *pthread_mutex_t) E;
@@ -11268,7 +11295,6 @@ pub const login_getcaptime = openbsd.login_getcaptime;
 pub const login_getclass = openbsd.login_getclass;
 pub const login_getstyle = openbsd.login_getstyle;
 pub const pledge = openbsd.pledge;
-pub const pthread_spinlock_t = openbsd.pthread_spinlock_t;
 pub const pw_dup = openbsd.pw_dup;
 pub const setclasscontext = openbsd.setclasscontext;
 pub const setpassent = openbsd.setpassent;

src/libs/mingw.zig

@@ -913,7 +913,6 @@ const mingw32_winpthreads_src = [_][]const u8{
     "winpthreads" ++ path.sep_str ++ "rwlock.c",
     "winpthreads" ++ path.sep_str ++ "sched.c",
     "winpthreads" ++ path.sep_str ++ "sem.c",
-    "winpthreads" ++ path.sep_str ++ "spinlock.c",
     "winpthreads" ++ path.sep_str ++ "thread.c",
 };
 

src/libs/musl.zig

@@ -1663,11 +1663,6 @@ const src_files = [_][]const u8{
     "musl/src/thread/pthread_setschedprio.c",
     "musl/src/thread/pthread_setspecific.c",
     "musl/src/thread/pthread_sigmask.c",
-    "musl/src/thread/pthread_spin_destroy.c",
-    "musl/src/thread/pthread_spin_init.c",
-    "musl/src/thread/pthread_spin_lock.c",
-    "musl/src/thread/pthread_spin_trylock.c",
-    "musl/src/thread/pthread_spin_unlock.c",
     "musl/src/thread/pthread_testcancel.c",
     "musl/src/thread/riscv32/clone.s",
     "musl/src/thread/riscv32/__set_thread_area.s",

src/libs/wasi_libc.zig

@@ -939,8 +939,6 @@ const libc_top_half_src_files = [_][]const u8{
     "musl/src/thread/pthread_setcancelstate.c",
     "musl/src/thread/pthread_setcanceltype.c",
     "musl/src/thread/pthread_setspecific.c",
-    "musl/src/thread/pthread_spin_destroy.c",
-    "musl/src/thread/pthread_spin_init.c",
     "musl/src/thread/pthread_testcancel.c",
     "musl/src/thread/thrd_sleep.c",
     "musl/src/time/asctime.c",
@@ -1086,9 +1084,6 @@ const libc_top_half_src_files = [_][]const u8{
     "wasi/thread-stub/pthread_rwlock_trywrlock.c",
     "wasi/thread-stub/pthread_rwlock_unlock.c",
     "wasi/thread-stub/pthread_rwlock_wrlock.c",
-    "wasi/thread-stub/pthread_spin_lock.c",
-    "wasi/thread-stub/pthread_spin_trylock.c",
-    "wasi/thread-stub/pthread_spin_unlock.c",
 };
 
 const crt1_command_src_file = "wasi/libc-bottom-half/crt/crt1-command.c";

test/c.zig

@@ -4,6 +4,7 @@ const std = @import("std");
 test {
     _ = @import("c/inttypes.zig");
     _ = @import("c/math.zig");
+    _ = @import("c/pthread.zig");
     _ = @import("c/search.zig");
     _ = @import("c/stdlib.zig");
     _ = @import("c/string.zig");

test/c/pthread.zig

@@ -0,0 +1,20 @@
+const builtin = @import("builtin");
+const std = @import("std");
+
+const c = std.c;
+const math = std.math;
+const testing = std.testing;
+
+test "pthread_spinlock_t" {
+    if (builtin.target.os.tag.isDarwin()) return; // Darwin doesn't have `pthread_spin_*`
+
+    var spin: c.pthread_spinlock_t = undefined;
+    _ = c.pthread_spin_init(&spin, c.PTHREAD_PROCESS_PRIVATE);
+    defer _ = c.pthread_spin_destroy(&spin);
+
+    try std.testing.expectEqual(@intFromEnum(c.E.SUCCESS), c.pthread_spin_trylock(&spin));
+    try std.testing.expectEqual(@intFromEnum(c.E.SUCCESS), c.pthread_spin_unlock(&spin));
+
+    try std.testing.expectEqual(@intFromEnum(c.E.SUCCESS), c.pthread_spin_lock(&spin));
+    try std.testing.expectEqual(@intFromEnum(c.E.SUCCESS), c.pthread_spin_unlock(&spin));
+}