cosmopolitan/third_party/nsync/mu_semaphore.c
Justine Tunney 49b0eaa69f
Improve threading and i/o routines
- On Windows connect() can now be interrupted by a signal; connect() w/
  O_NONBLOCK will now raise EINPROGRESS; and connect() with SO_SNDTIMEO
  will raise ETIMEDOUT after the interval has elapsed.

- We now get the AcceptEx(), ConnectEx(), and TransmitFile() functions
  from the WIN32 API the officially blessed way, using WSAIoctl().

- Do nothing on Windows when fsync() is called on a directory handle.
  This was raising EACCES earlier becaues GENERIC_WRITE is required on
  the handle. It's possible to FlushFileBuffers() a directory handle if
  it's opened with write access but MSDN doesn't document what it does.
  If you have any idea, please let us know!

- Prefer manual reset event objects for read() and write() on Windows.

- Do some code cleanup on our dlmalloc customizations.

- Fix errno type error in Windows blocking routines.

- Make the futex polyfill simpler and faster.
2023-10-12 23:13:04 -07:00

109 lines
4.8 KiB
C

/*-*- mode:c;indent-tabs-mode:t;c-basic-offset:8;tab-width:8;coding:utf-8 -*-│
│vi: set et ft=c ts=8 tw=8 fenc=utf-8 :vi│
╞══════════════════════════════════════════════════════════════════════════════╡
│ Copyright 2016 Google Inc. │
│ │
│ Licensed under the Apache License, Version 2.0 (the "License"); │
│ you may not use this file except in compliance with the License. │
│ You may obtain a copy of the License at │
│ │
│ http://www.apache.org/licenses/LICENSE-2.0 │
│ │
│ Unless required by applicable law or agreed to in writing, software │
│ distributed under the License is distributed on an "AS IS" BASIS, │
│ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. │
│ See the License for the specific language governing permissions and │
│ limitations under the License. │
╚─────────────────────────────────────────────────────────────────────────────*/
#include "third_party/nsync/mu_semaphore.h"
#include "libc/calls/cp.internal.h"
#include "libc/dce.h"
#include "third_party/nsync/mu_semaphore.internal.h"
/* Apple's ulock (part by Cosmo futexes) is an internal API, but:
1. Unlike GCD it's cancellable, i.e. can be EINTR'd by signals
2. We currently always use ulock anyway for joining threads */
#define PREFER_GCD_OVER_ULOCK 1
asm(".ident\t\"\\n\\n\
*NSYNC (Apache 2.0)\\n\
Copyright 2016 Google, Inc.\\n\
https://github.com/google/nsync\"");
// clang-format off
/* Initialize *s; the initial value is 0. */
void nsync_mu_semaphore_init (nsync_semaphore *s) {
if (PREFER_GCD_OVER_ULOCK && IsXnuSilicon ()) {
return nsync_mu_semaphore_init_gcd (s);
} else if (IsNetbsd ()) {
return nsync_mu_semaphore_init_sem (s);
} else if (IsWindows ()) {
return nsync_mu_semaphore_init_win32 (s);
} else {
return nsync_mu_semaphore_init_futex (s);
}
}
/* Releases system resources associated with *s. */
void nsync_mu_semaphore_destroy (nsync_semaphore *s) {
if (PREFER_GCD_OVER_ULOCK && IsXnuSilicon ()) {
return nsync_mu_semaphore_destroy_gcd (s);
} else if (IsNetbsd ()) {
return nsync_mu_semaphore_destroy_sem (s);
} else if (IsWindows ()) {
return nsync_mu_semaphore_destroy_win32 (s);
}
}
/* Wait until the count of *s exceeds 0, and decrement it. If POSIX cancellations
are currently disabled by the thread, then this function always succeeds. When
they're enabled in MASKED mode, this function may return ECANCELED. Otherwise,
cancellation will occur by unwinding cleanup handlers pushed to the stack. */
errno_t nsync_mu_semaphore_p (nsync_semaphore *s) {
errno_t err;
BEGIN_CANCELATION_POINT;
if (PREFER_GCD_OVER_ULOCK && IsXnuSilicon ()) {
err = nsync_mu_semaphore_p_gcd (s);
} else if (IsNetbsd ()) {
err = nsync_mu_semaphore_p_sem (s);
} else if (IsWindows ()) {
err = nsync_mu_semaphore_p_win32 (s);
} else {
err = nsync_mu_semaphore_p_futex (s);
}
END_CANCELATION_POINT;
return err;
}
/* Like nsync_mu_semaphore_p() this waits for the count of *s to exceed 0,
while additionally supporting a time parameter specifying at what point
in the future ETIMEDOUT should be returned, if neither cancelation, or
semaphore release happens. */
errno_t nsync_mu_semaphore_p_with_deadline (nsync_semaphore *s, nsync_time abs_deadline) {
errno_t err;
BEGIN_CANCELATION_POINT;
if (PREFER_GCD_OVER_ULOCK && IsXnuSilicon ()) {
err = nsync_mu_semaphore_p_with_deadline_gcd (s, abs_deadline);
} else if (IsNetbsd ()) {
err = nsync_mu_semaphore_p_with_deadline_sem (s, abs_deadline);
} else if (IsWindows ()) {
err = nsync_mu_semaphore_p_with_deadline_win32 (s, abs_deadline);
} else {
err = nsync_mu_semaphore_p_with_deadline_futex (s, abs_deadline);
}
END_CANCELATION_POINT;
return err;
}
/* Ensure that the count of *s is at least 1. */
void nsync_mu_semaphore_v (nsync_semaphore *s) {
if (PREFER_GCD_OVER_ULOCK && IsXnuSilicon ()) {
return nsync_mu_semaphore_v_gcd (s);
} else if (IsNetbsd ()) {
return nsync_mu_semaphore_v_sem (s);
} else if (IsWindows ()) {
return nsync_mu_semaphore_v_win32 (s);
} else {
return nsync_mu_semaphore_v_futex (s);
}
}