The Windows error for a refused FindFirstChangeNotification was one string shared
by WatchParent and WatchContents, so the log could not tell which handle or path
was denied. Build it from the watcher, the path the API was given and
GetLastError instead.
Still throws: the EVFILT_VNODE attach path is vfs_kqfilter, which returns only
EINVAL, ENOMEM or 0, with EBADF from fget before it, and consults no directory
permission, so no FreeBSD errno stands for a host that refuses to notify.
Windows 10 1903 deletes a file with open handles by moving it into
$Extend\$Deleted until the last handle closes, so the next snapshot of a
watched file that a title (or the test) deleted saw a new path, tried to
watch that directory's changes, got ERROR_ACCESS_DENIED and threw from
the watch thread, which aborts the process; the path change was also
reported as NOTE_RENAME next to NOTE_DELETE. A snapshot with a pending
delete or no links now reports NOTE_DELETE alone and drops the parent
directory watch instead of replacing it, as the file has no directory
to be renamed or removed from any more.
inotify queues IN_MOVED_FROM and IN_MOVED_TO of a rename one after the
other. The watcher thread could read the first before the second was
queued and report a rename inside the directory as a move to another
directory (NOTE_WRITE | NOTE_EXTEND instead of NOTE_WRITE), which made
guest_kqueue abort on loaded runners.
The watcher now reads the queue until it is empty and, when a move half
has no partner, calls getdents64 on the directory before reading again:
that takes the directory lock rename holds until both halves are queued.
Cloudberry Kingdom (PPSA23827, #3177) registers its first kevent change
as a file watch: ident 3, EVFILT_VNODE, flags 0x25
(EV_ADD|EV_ENABLE|EV_CLEAR), fflags 0x37
(NOTE_DELETE|WRITE|EXTEND|LINK|RENAME). Palworld's Discord module
(PPSA23126, #2648) imports sceKernelAddFileEvent and
sceKernelDeleteFileEvent, which no library exported.
EVFILT_VNODE watches the host file or directory behind the descriptor
and turns host changes into FreeBSD 11 vnode hints, added whole when
they share a bit with the requested fflags as filt_vfsvnode does
(sys/kern/vfs_subr.c, release/11.0.1 34bd3475): a growing write is
NOTE_WRITE|NOTE_EXTEND, a shrinking truncate or an attribute change
NOTE_ATTRIB, a link count change NOTE_LINK or NOTE_DELETE, a pending
delete NOTE_DELETE, a new path NOTE_RENAME, and in a directory a new,
removed or renamed entry NOTE_WRITE (with NOTE_LINK for a subdirectory,
as vop_mkdir_post/vop_rmdir_post). Windows uses FindFirstChangeNotification
on the parent directory (and the watched directory) and compares handle
snapshots every 50 ms, since a write through an open handle is not
reported until it is flushed or closed (measured); Linux uses inotify.
Closing the descriptor, deleting the event or the queue stops the
watcher.
sceKernelAddFileEvent(eq, fd, watch, udata) and
sceKernelDeleteFileEvent(eq, fd) take the OpenOrbis 0a1aaf9d
(libkernel.h:35,109) and SharpProspero 5dfdb4b0 (KernelEqueue.cs:164,168)
signatures; NIDs cG3t15OK4Ow and UmXngHKB6is confirmed with
tools/nid_names.py. The watch bits are the fflags and the event is added
with EV_CLEAR, which is not confirmed on a title.
Throws: NOTE_REVOKE, NOTE_OPEN, NOTE_CLOSE, NOTE_CLOSE_WRITE, NOTE_READ
and unknown bits, NOTE_EXTEND on a directory on Windows (a move from
another directory cannot be told from a creation) and descriptors that
are not files, directories, pipes or sockets (pipes, sockets and kqueues
fail with EINVAL as in FreeBSD). Recorded in TechnicalDebt.
guest_kqueue adds a vnode watch that sees a write to a temporary file
with Cloudberry's flags, fflags filtering, a re-registration, the sce
pair on an equeue, EINVAL for sockets, pipes and the kqueue itself, the
close of a watched descriptor and a directory watch.
Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Cloudberry Kingdom (PPSA23827, #3177) calls kqueue right after start-up
and stopped on the throwing declarations merged with #3337; Palworld's
Discord module (PPSA23126, #2648) imports kevent.
kqueue reserves a host null-device descriptor in the file descriptor
space and registers it as an event queue that reports each ready event
once per call and moves level-triggered ones behind the others, as
kqueue_scan does. close and sceKernelClose close the queue and drop the
descriptor's events from every queue, dup2 drops them for the target,
and dup/dup2 of a kqueue throw, so a reused descriptor number is never
read as a stale kqueue.
kevent follows FreeBSD 11 kern_event.c (release/11.0.1 34bd3475):
kqueue_kevent for the changelist (filter 0 skipped, EV_SYSFLAGS
cleared, EV_ERROR receipts with the errno in data, EV_RECEIPT, the
early return when nevents is exhausted), kqueue_register for EV_ADD,
EV_DELETE, EV_ENABLE, EBADF, ENOENT and EINVAL, kqueue_scan for the
timeout (EINVAL for a bad timespec, zero polls, above INT32_MAX waits
forever) and filt_timerattach, filt_usertouch for the timer and user
filters. Read and write events reuse the guest socket poll of
sceKernelAddReadEvent/WriteEvent.
Throws: other filters, EV_DISABLE, EV_DISPATCH, EV_FORCEONESHOT,
NOTE_LOWAT, EV_CLEAR on a socket, read/write events on non-socket
descriptors or another kqueue, changes to an existing timer (11.0 and
11.4 differ), a NOTE_NSECONDS fraction above one second and a negative
nevents. Recorded in TechnicalDebt.
Test guest_kqueue covers creation and close, timers, a user event
triggered from another thread, read and write events on a socket pair,
EV_ERROR receipts, the timeout and the error cases.
Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
