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https://github.com/jart/cosmopolitan.git
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af7bd80430
This change introduces a new deadlock detector for Cosmo's POSIX threads implementation. Error check mutexes will now track a DAG of nested locks and report EDEADLK when a deadlock is theoretically possible. These will occur rarely, but it's important for production hardening your code. You don't even need to change your mutexes to use the POSIX error check mode because `cosmocc -mdbg` will enable error checking on mutexes by default globally. When cycles are found, an error message showing your demangled symbols describing the strongly connected component are printed and then the SIGTRAP is raised, which means you'll also get a backtrace if you're using ShowCrashReports() too. This new error checker is so low-level and so pure that it's able to verify the relationships of every libc runtime lock, including those locks upon which the mutex implementation depends.
83 lines
3.3 KiB
C
83 lines
3.3 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 2021 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/calls.h"
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#include "libc/errno.h"
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#include "libc/macros.h"
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#include "libc/stdio/internal.h"
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#include "libc/stdio/stdio.h"
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#include "libc/sysv/consts/o.h"
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/**
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* Repositions open file stream.
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*
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* This function flushes the buffer (unless it's currently in the EOF
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* state) and then calls lseek() on the underlying file. If the stream
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* is in the EOF state, this function can be used to restore it without
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* needing to reopen the file.
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*
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* @param f is a non-null stream handle
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* @param offset is the byte delta
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* @param whence can be SEET_SET, SEEK_CUR, or SEEK_END
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* @returns 0 on success or -1 w/ errno
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*/
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int fseek_unlocked(FILE *f, int64_t offset, int whence) {
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int res;
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int64_t pos;
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if (f->fd != -1) {
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if (fflush_unlocked(f) == EOF)
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return -1;
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if (whence == SEEK_CUR && f->beg < f->end) {
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offset -= f->end - f->beg;
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}
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if (lseek(f->fd, offset, whence) != -1) {
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f->beg = 0;
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f->end = 0;
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f->state = 0;
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res = 0;
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} else {
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f->state = errno == ESPIPE ? EBADF : errno;
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res = -1;
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}
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} else {
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switch (whence) {
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case SEEK_SET:
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pos = offset;
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break;
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case SEEK_CUR:
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pos = f->beg + offset;
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break;
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case SEEK_END:
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pos = f->end + offset;
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break;
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default:
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pos = -1;
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break;
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}
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f->end = MAX(f->beg, f->end);
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if (0 <= pos && pos <= f->end) {
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f->beg = pos;
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f->state = 0;
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res = 0;
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} else {
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f->state = errno = EINVAL;
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res = -1;
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}
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}
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return res;
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}
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