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https://github.com/jart/cosmopolitan.git
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1bf2d8e308
The way to use double linked lists, is to remove all the things you want to work on, insert them into a new list on the stack. Then once you have all the work items, you release the lock, do your work, and then lock it again, to add the shelled out items back to a global freelist.
93 lines
3.6 KiB
C
93 lines
3.6 KiB
C
/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
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│ vi: set et ft=c ts=2 sts=2 sw=2 fenc=utf-8 :vi │
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╞══════════════════════════════════════════════════════════════════════════════╡
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│ Copyright 2020 Justine Alexandra Roberts Tunney │
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│ │
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│ Permission to use, copy, modify, and/or distribute this software for │
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│ any purpose with or without fee is hereby granted, provided that the │
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│ above copyright notice and this permission notice appear in all copies. │
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│ │
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│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL │
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│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED │
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│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE │
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│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL │
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│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR │
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│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER │
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│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR │
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│ PERFORMANCE OF THIS SOFTWARE. │
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╚─────────────────────────────────────────────────────────────────────────────*/
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#include "libc/calls/internal.h"
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#include "libc/calls/state.internal.h"
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#include "libc/calls/struct/fd.internal.h"
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#include "libc/intrin/atomic.h"
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#include "libc/intrin/cmpxchg.h"
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#include "libc/intrin/extend.internal.h"
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#include "libc/macros.internal.h"
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#include "libc/runtime/memtrack.internal.h"
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#include "libc/str/str.h"
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#include "libc/sysv/consts/map.h"
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/**
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* Grows file descriptor array memory if needed.
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*
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* @see libc/runtime/memtrack64.txt
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* @see libc/runtime/memtrack32.txt
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* @asyncsignalsafe
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*/
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int __ensurefds_unlocked(int fd) {
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size_t n;
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if (fd < g_fds.n)
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return fd;
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n = fd + 1;
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g_fds.e = _extend(g_fds.p, n * sizeof(*g_fds.p), g_fds.e, MAP_PRIVATE,
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kMemtrackFdsStart + kMemtrackFdsSize);
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g_fds.n = n;
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return fd;
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}
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/**
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* Grows file descriptor array memory if needed.
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* @asyncsignalsafe
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*/
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int __ensurefds(int fd) {
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__fds_lock();
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fd = __ensurefds_unlocked(fd);
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__fds_unlock();
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return fd;
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}
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/**
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* Finds open file descriptor slot.
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* @asyncsignalsafe
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*/
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int __reservefd_unlocked(int start) {
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int fd, f1, f2;
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for (;;) {
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f1 = atomic_load_explicit(&g_fds.f, memory_order_acquire);
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for (fd = MAX(start, f1); fd < g_fds.n; ++fd)
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if (!g_fds.p[fd].kind)
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break;
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fd = __ensurefds_unlocked(fd);
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bzero(g_fds.p + fd, sizeof(*g_fds.p));
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if (_cmpxchg(&g_fds.p[fd].kind, kFdEmpty, kFdReserved)) {
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// g_fds.f isn't guarded by our mutex
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do {
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f2 = MAX(fd + 1, f1);
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} while (!atomic_compare_exchange_weak_explicit(
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&g_fds.f, &f1, f2, memory_order_release, memory_order_relaxed));
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return fd;
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}
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}
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}
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/**
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* Finds open file descriptor slot.
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* @asyncsignalsafe
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*/
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int __reservefd(int start) {
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int fd;
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__fds_lock();
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fd = __reservefd_unlocked(start);
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__fds_unlock();
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return fd;
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}
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