file descriptor opened for complimentary access exists as well.
The implementation of the guarantee is done by counting the
generations of readers and writers opens. We return success and not
EINTR or ERESTART error, when the sleep for complimentary opening is
interrupted, but the generation was changed during the sleep.
Longer explanation: assume there are two threads, A doing open("fifo",
O_RDONLY) and B doing open("fifo", O_WRONLY), and no other threads
either trying to open the fifo, nor there are any file descriptors
referencing the fifo. Before the change, it was possible e.g. for for
thread A to return a valid file descriptor, while thread B returned
EINTR if a signal to B was delivered simultaneously with the wakeup
from A. After the change, in this situation both A::open() and
B::open() succeed and the signal is made "as if" it was noticed
slightly later. Note that the signal actual delivery is not changed,
it is done by ast on syscall return path, so signal handler is still
executed before first instruction after syscall.
See PR for the code demonstrating the issue.
PR: 203162
Reported by: Victor Stinner victor.stinner@gmail.com
Reviewed by: jilles
Tested by: bapt, pho
Sponsored by: The FreeBSD Foundation
MFC after: 1 week
It can fail if pipe map is exhausted (as a result of too many pipes created),
but it is not fatal and could be provoked by unprivileged users. The only
consequence is worse performance with given pipe.
Reported by: ivoras
Suggested by: kib
MFC after: 1 week
Besides not making sense, open(O_EXEC) for fifo creates fifoinfo with
zero readers and writers counts, which causes premature free of pipes.
Reported and tested by: pho
Sponsored by: The FreeBSD Foundation
MFC after: 1 week
I found 8.3 is a history BSD version using socket to implement FIFO
pipe, it uses per-file seqcount to compare with writer generation
stored in per-pipe object. The concept is after all writers are gone,
the pipe enters next generation, all old readers have not closed the
pipe should get the indication that the pipe is disconnected, result
is they should get EPIPE, SIGPIPE or get POLLHUP in poll().
But newcomer should not know that previous writters were gone, it
should treat it as a fresh session.
I am trying to bring back FIFO pipe to history behavior. It is still
unclear that if single EOF flag can represent SBS_CANTSENDMORE and
SBS_CANTRCVMORE which socket-based version is using, but I have run
the poll regression test in tool directory, output is same as the one
on 8.3-STABLE now.
I think the output "not ok 18 FIFO state 6b: poll result 0 expected 1.
expected POLLHUP; got 0" might be bogus, because newcomer should not
know that old writers were gone. I got the same behavior on Linux.
Our implementation always return POLLIN for disconnected pipe even it
should return POLLHUP, but I think it is not wise to remove POLLIN for
compatible reason, this is our history behavior.
Regression test: /usr/src/tools/regression/poll
flag but not PIPE_WANTW, but FIFO pipe code does not understand this internal
state, when a FIFO peer reader closes the pipe, it wants to notify the writer,
it checks PIPE_WANTW, if not set, it skips calling wakeup(), so blocked writer
never noticed the case, but in general, the writer should return from the
syscall with EPIPE error code and may get SIGPIPE signal. Setting the
PIPE_WANTW fixed problem, or you can turn off direct write, it should fix the
problem too. This bug is found by PR/170203.
Another bug in FIFO pipe code is when peer closes the pipe, another end which
is being blocked in select() or poll() is not notified, it missed to call
pipeselwakeup().
Third problem is found in poll regression test, the existing code can not
pass 6b,6c,6d tests, but FreeBSD-4 works. This commit does not fix the
problem, I still need to study more to find the cause.
PR: 170203
Tested by: Garrett Copper < yanegomi at gmail dot com >
fifo_iseof() condition, allowing the v_fifoinfo to be reset and freed
by fifo_cleanup().
Precalculate EOF at the places were fo_wgen is changed, and cache the
state in a new pipe state flag PIPE_SAMEWGEN.
Reported and tested by: bf
Submitted by: gianni
MFC after: 1 week (a backport)
difference between fi_wgen and f_seqcount, so the change is purely
cosmetic, but it makes the code easier to understand.
Submitted by: gianni
MFC after: 2 weeks
to implement fchown(2) and fchmod(2) support for several file types
that previously lacked it. Add MAC entries for chown/chmod done on
posix shared memory and (old) in-kernel posix semaphores.
Based on the submission by: glebius
Reviewed by: rwatson
Approved by: re (bz)
want to provide VOP_ACCESSX(9) don't have to implement both. Note that
this commit makes implementation of either of these two mandatory.
Reviewed by: kib
This reverts part of r196460, so that sockets only return POLLHUP if both
directions are closed/error. Fifos get POLLHUP by closing the unused
direction immediately after creating the sockets.
The tools/regression/poll/*poll.c tests now pass except for two other things:
- if POLLHUP is returned, POLLIN is always returned as well instead of only
when there is data left in the buffer to be read
- fifo old/new reader distinction does not work the way POSIX specs it
Reviewed by: kib, bde
when all writers, observed by reader, exited. Use writer generation
counter for fifo, and store the snapshot of the fifo generation in the
f_seqcount field of struct file, that is otherwise unused for fifos.
Set FreeBSD-undocumented POLLINIGNEOF flag only when file f_seqcount is
equal to fifo' fi_wgen, and revert r89376.
Fix POLLINIGNEOF for sockets and pipes, and return POLLHUP for them.
Note that the patch does not fix not returning POLLHUP for fifos.
PR: kern/94772
Submitted by: bde (original version)
Reviewed by: rwatson, jilles
Approved by: re (kensmith)
MFC after: 6 weeks (might be)
the removal of NQNFS, but was left in in case it was required for NFSv4.
Since our new NFSv4 client and server can't use it for their
requirements, GC the old mechanism, as well as other unused lease-
related code and interfaces.
Due to its impact on kernel programming and binary interfaces, this
change should not be MFC'd.
Proposed by: jeff
Reviewed by: jeff
Discussed with: rmacklem, zach loafman @ isilon
- Align the fifo output in fifo_print() with other vn_printf() output.
- Remove the leading space from lockmgr_printinfo() so its output lines up
in vn_printf().
- lockmgr_printinfo() now ends with a newline, so remove an extra newline
from vn_printf().
without corresponding number of fifo_open(). This causes assertion
failure in fifo_close() due to vp->v_fifoinfo being NULL for kernel
with INVARIANTS, or NULL pointer dereference otherwise. In fact, we may
ignore excess calls to fifo_close() without bad consequences.
Turn KASSERT() into the return, and print warning for now.
Tested by: pho
Reviewed by: rwatson
MFC after: 2 weeks
While the KSE project was quite successful in bringing threading to
FreeBSD, the M:N approach taken by the kse library was never developed
to its full potential. Backwards compatibility will be provided via
libmap.conf for dynamically linked binaries and static binaries will
be broken.
bug that caused us to reintroduce it is believed to be fixed, and Kris
says he no longer sees problems with fifofs in highly parallel builds.
If this works out, we'll MFC it for 7.1.
MFC after: 3 months
Pointed out by: kris
conjuction with 'thread' argument passing which is always curthread.
Remove the unuseful extra-argument and pass explicitly curthread to lower
layer functions, when necessary.
KPI results broken by this change, which should affect several ports, so
version bumping and manpage update will be further committed.
Tested by: kris, pho, Diego Sardina <siarodx at gmail dot com>
Remove this argument and pass curthread directly to underlying
VOP_LOCK1() VFS method. This modify makes the code cleaner and in
particular remove an annoying dependence helping next lockmgr() cleanup.
KPI results, obviously, changed.
Manpage and FreeBSD_version will be updated through further commits.
As a side note, would be valuable to say that next commits will address
a similar cleanup about VFS methods, in particular vop_lock1 and
vop_unlock.
Tested by: Diego Sardina <siarodx at gmail dot com>,
Andrea Di Pasquale <whyx dot it at gmail dot com>
This makes it possible to support ftruncate() on non-vnode file types in
the future.
- 'struct fileops' grows a 'fo_truncate' method to handle an ftruncate() on
a given file descriptor.
- ftruncate() moves to kern/sys_generic.c and now just fetches a file
object and invokes fo_truncate().
- The vnode-specific portions of ftruncate() move to vn_truncate() in
vfs_vnops.c which implements fo_truncate() for vnode file types.
- Non-vnode file types return EINVAL in their fo_truncate() method.
Submitted by: rwatson
- Introduce a finit() which is used to initailize the fields of struct file
in such a way that the ops vector is only valid after the data, type,
and flags are valid.
- Protect f_flag and f_count with atomic operations.
- Remove the global list of all files and associated accounting.
- Rewrite the unp garbage collection such that it no longer requires
the global list of all files and instead uses a list of all unp sockets.
- Mark sockets in the accept queue so we don't incorrectly gc them.
Tested by: kris, pho
Change the VOP_OPEN(), vn_open() vnode operation and d_fdopen() cdev operation
argument from being file descriptor index into the pointer to struct file.
Proposed and reviewed by: jhb
Reviewed by: daichi (unionfs)
Approved by: re (kensmith)
and flags with an sxlock. This leads to a significant and measurable
performance improvement as a result of access to shared locking for
frequent lookup operations, reduced general overhead, and reduced overhead
in the event of contention. All of these are imported for threaded
applications where simultaneous access to a shared file descriptor array
occurs frequently. Kris has reported 2x-4x transaction rate improvements
on 8-core MySQL benchmarks; smaller improvements can be expected for many
workloads as a result of reduced overhead.
- Generally eliminate the distinction between "fast" and regular
acquisisition of the filedesc lock; the plan is that they will now all
be fast. Change all locking instances to either shared or exclusive
locks.
- Correct a bug (pointed out by kib) in fdfree() where previously msleep()
was called without the mutex held; sx_sleep() is now always called with
the sxlock held exclusively.
- Universally hold the struct file lock over changes to struct file,
rather than the filedesc lock or no lock. Always update the f_ops
field last. A further memory barrier is required here in the future
(discussed with jhb).
- Improve locking and reference management in linux_at(), which fails to
properly acquire vnode references before using vnode pointers. Annotate
improper use of vn_fullpath(), which will be replaced at a future date.
In fcntl(), we conservatively acquire an exclusive lock, even though in
some cases a shared lock may be sufficient, which should be revisited.
The dropping of the filedesc lock in fdgrowtable() is no longer required
as the sxlock can be held over the sleep operation; we should consider
removing that (pointed out by attilio).
Tested by: kris
Discussed with: jhb, kris, attilio, jeff
rather than panicking later. This can occur if the kernel calls
vn_open() on a fifo, as there will be no associated file descriptor,
and therefore the file descriptor operations cannot be modified to
point to the fifo operation set.
MFC after: 3 days
Reported by: Martin <nakal at nurfuerspam dot de>
PR: 94278
a fifo. While this did indeed close the race, confirming suspicions
about the nature of the problem, it causes difficulties with blocking
I/O on fifos.
Discussed with: ups
Also spotted by: Peter Holm <peter at holm dot cc>
that socket during open, not the write socket receive buffer. This
might explain clearing of the sb_state SB_LOCK flag seen occasionally
in soreceive() on fifos.
MFC after: 3 days
Spotted by: ups
underlying the POSIX fifo implementation. In 6.x/7.x, fifo access is
moved from the VFS layer, where it was serialized using the vnode
lock, to the file descriptor layer, where access is protected by a
reference count but not serialized. This exposed socket buffer
locking to high levels of parallelism in specific fifo workloads, such
as make -j 32, which expose as yet unresolved socket buffer bugs.
fi_sx re-adds serialization about the read and write routines,
although not paths that simply test socket buffer mbuf queue state,
such as the poll and kqueue methods. This restores the extra locking
cost previously present in some cases, but is an effective workaround
for the instability that has been experienced. This workaround should
be removed once the bug in socket buffer handling has been fixed.
Reported by: kris, jhb, Julien Gabel <jpeg at thilelli dot net>,
Peter Holm <peter at holm dot cc>, others
MFC after: 3 days
fifo_kqfilter() VOP implementations, since they in theory are used
only on open file descriptors, in which case the ioctls are via
fifo_ioctl_f() and kqueue requests are via fifo_kqfilter_f().
Generate warnings if they are entered for now. These printf()
calls should become panic() calls.
Annotate and re-implement fifo_ioctl_f(): don't arbitrarily
forward ioctls to the socket layer, only forward the ones we
explicitly support for fifos. In the case of FIONREAD, don't
forward the request to the write socket on a read-write fifo, or
the read result is overwritten. Annotate a nasty case for the
undefined POSIX O_RDWR on fifos, in which failure of the second
ioctl will result in the socket pair being in an inconsistent
state.
Assert copyright as I find myself rewriting non-trivial parts of
fifofs.
MFC after: 3 days
be held when entering a kqueue filter for fifos via a socket buffer
event: as such, assert the lock unconditionally rather than acquiring
it conditionall.
MFC after: 3 days
1) fifo_kqfilter() is not actually ever used, it likely should be GC'd.
2) fifo_kqfilter_f() doesn't implement EVFILT_VNODE, so detecting events
on the underlying vnode for a fifo no longer works (it did in 4.x).
Likely, fifo_kqfilter_f() should forward the request to the VFS using
fp->f_vnode, which would work once fifo_kqfilter() was detached from
the vnode operation vector (removing the fifo override).
Discussed with: phk
used when a read filter is requested on a write-only fifo descriptor, or
a write filter is requested on a read-only fifo descriptor. This
permits the filters to be registered, but never raises the event, which
causes kqueue behavior for fifos to more closely match similar semantics
for poll and select, which permit testing for the condition even though
the condition will never be raised, and is consistent with POSIX's notion
that a fifo has identical semantics to a one-way IPC channel created
using pipe() on most operating systems.
The fifo regression test suite can now run to completion on HEAD without
errors.
MFC after: 3 days
according to POSIX, not to mention the fact that it doesn't make sense
(and hence isn't really implemented). This causes the fifo_misc
regression test to succeed.
