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Share file offset across processes

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This change ensures that if a file descriptor for an open disk file gets
shared by multiple processes within a process tree, then lseek() changes
will be visible across processes, and read() / write() are synchronized.
Note this only applies to Windows, because UNIX kernels already do this.
This commit is contained in:
Justine Tunney 2024-08-03 01:24:46 -07:00
parent a80ab3f8fe
commit 761c6ad615
No known key found for this signature in database
GPG key ID: BE714B4575D6E328
15 changed files with 256 additions and 63 deletions
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15
libc/calls/fcntl-nt.c
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@ -20,13 +20,13 @@
#include "libc/calls/calls.h"
#include "libc/calls/createfileflags.internal.h"
#include "libc/calls/internal.h"
#include "libc/intrin/fds.h"
#include "libc/calls/struct/flock.h"
#include "libc/calls/struct/sigset.internal.h"
#include "libc/calls/syscall-nt.internal.h"
#include "libc/calls/syscall_support-nt.internal.h"
#include "libc/calls/wincrash.internal.h"
#include "libc/errno.h"
#include "libc/intrin/fds.h"
#include "libc/intrin/kprintf.h"
#include "libc/intrin/weaken.h"
#include "libc/limits.h"
@ -151,7 +151,7 @@ static textwindows int sys_fcntl_nt_lock(struct Fd *f, int fd, int cmd,
case SEEK_SET:
break;
case SEEK_CUR:
off = f->pointer + off;
off = f->shared->pointer + off;
break;
case SEEK_END: {
int64_t size;
@ -351,9 +351,14 @@ textwindows int sys_fcntl_nt(int fd, int cmd, uintptr_t arg) {
}
rc = 0;
} else if (cmd == F_SETLK || cmd == F_SETLKW || cmd == F_GETLK) {
pthread_mutex_lock(&g_locks.mu);
rc = sys_fcntl_nt_lock(g_fds.p + fd, fd, cmd, arg);
pthread_mutex_unlock(&g_locks.mu);
struct Fd *f = g_fds.p + fd;
if (f->shared) {
pthread_mutex_lock(&g_locks.mu);
rc = sys_fcntl_nt_lock(f, fd, cmd, arg);
pthread_mutex_unlock(&g_locks.mu);
} else {
rc = ebadf();
}
} else if (cmd == F_DUPFD || cmd == F_DUPFD_CLOEXEC) {
rc = sys_fcntl_nt_dupfd(fd, cmd, arg);
} else {