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Implement pthread_atfork()

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If threads are being used, then fork() will now acquire and release and
runtime locks so that fork() may be safely used from threads. This also
makes vfork() thread safe, because pthread mutexes will do nothing when
the process is a child of vfork(). More torture tests have been written
to confirm this all works like a charm. Additionally:

- Invent hexpcpy() api
- Rename nsync_malloc_() to kmalloc()
- Complete posix named semaphore implementation
- Make pthread_create() asynchronous signal safe
- Add rm, rmdir, and touch to command interpreter builtins
- Invent sigisprecious() and modify sigset functions to use it
- Add unit tests for posix_spawn() attributes and fix its bugs

One unresolved problem is the reclaiming of *NSYNC waiter memory in the
forked child processes, within apps which have threads waiting on locks
This commit is contained in:
Justine Tunney 2022-10-16 12:05:08 -07:00
parent 64c284003d
commit 60cb435cb4
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GPG key ID: BE714B4575D6E328
124 changed files with 2169 additions and 718 deletions
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16
third_party/nsync/futex.c vendored
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@ -43,8 +43,6 @@
#include "third_party/nsync/time.h"
// clang-format off
/* futex() polyfill w/ sched_yield() fallback */
#define FUTEX_WAIT_BITS_ FUTEX_BITSET_MATCH_ANY
int _futex (atomic_int *, int, int, const struct timespec *, int *, int);
@ -161,6 +159,11 @@ int nsync_futex_wait_ (atomic_int *w, int expect, char pshare, struct timespec *
op |= FUTEX_PRIVATE_FLAG_;
}
LOCKTRACE ("futex(%t [%d], %s, %#x, %s) → ...",
w, atomic_load_explicit (w, memory_order_relaxed),
DescribeFutexOp (op), expect,
DescribeTimespec (0, timeout));
if (FUTEX_IS_SUPPORTED) {
if (IsWindows ()) {
// Windows 8 futexes don't support multiple processes :(
@ -199,7 +202,8 @@ int nsync_futex_wait_ (atomic_int *w, int expect, char pshare, struct timespec *
}
STRACE ("futex(%t [%d], %s, %#x, %s) → %s",
w, *w, DescribeFutexOp (op), expect,
w, atomic_load_explicit (w, memory_order_relaxed),
DescribeFutexOp (op), expect,
DescribeTimespec (0, timeout),
DescribeErrnoResult (rc));
@ -208,7 +212,7 @@ int nsync_futex_wait_ (atomic_int *w, int expect, char pshare, struct timespec *
int nsync_futex_wake_ (atomic_int *w, int count, char pshare) {
int e, rc, op, fop;
int wake (void *, int, int) asm ("_futex");
int wake (atomic_int *, int, int) asm ("_futex");
ASSERT (count == 1 || count == INT_MAX);
@ -245,8 +249,8 @@ int nsync_futex_wake_ (atomic_int *w, int count, char pshare) {
}
STRACE ("futex(%t [%d], %s, %d) → %s",
w, *w, DescribeFutexOp(op),
count, DescribeErrnoResult(rc));
w, atomic_load_explicit (w, memory_order_relaxed),
DescribeFutexOp(op), count, DescribeErrnoResult(rc));
return rc;
}