if we hold a spin mutex, since we can trivially get into deadlocks if we
start switching out of processes that hold spinlocks. Checking to see if
interrupts were disabled was a sort of cheap way of doing this since most
of the time interrupts were only disabled when holding a spin lock. At
least on the i386. To fix this properly, use a per-process counter
p_spinlocks that counts the number of spin locks currently held, and
instead of checking to see if interrupts are disabled in the witness code,
check to see if we hold any spin locks. Since child processes always
start up with the sched lock magically held in fork_exit(), we initialize
p_spinlocks to 1 for child processes. Note that proc0 doesn't go through
fork_exit(), so it starts with no spin locks held.
Consulting from: cp
into an interruptable sleep and we increment a sleep count, we make sure
that we are the thread that will decrement the count when we wakeup.
Otherwise, what happens is that if we get interrupted (signal) and we
have to wake up, but before we get our mutex, some thread that wants
to wake us up detects that the count is non-zero and so enters wakeup_one(),
but there's nothing on the sleep queue and so we don't get woken up. The
thread will still decrement the sleep count, which is bad because we will
also decrement it again later (as we got interrupted) and are already off
the sleep queue.
more robust. They would correctly return ENOMEM for the first time when
the buffer was exhausted, but subsequent calls in this case could cause
writes ouside of the buffer bounds.
Approved by: rwatson
structure rather than assuming that the device vnode would reside
in the FFS filesystem (which is obviously a broken assumption with
the device filesystem).
in the hopes that they will actually *read* the comment above
it and *follow* the instructions so as to cause all the rest
of us less a lot less grief.
- Don't try to grab Giant before postsig() in userret() as it is no longer
needed.
- Don't grab Giant before psignal() in ast() but get the proc lock instead.
Giant. The only exception is the CANSIGNAL() macro. Unlocking the proc
lock around sendsig() in trapsignal() is also questionable. Note that
the functions sigexit(), psignal(), and issignal() must be called with
the proc lock of the process in question held. postsig() and
trapsignal() should not be called with the proc lock held, but they
also do not require Giant anymore either.
- Remove spl's that are now no longer needed as they are fully replaced.
don't end up back at ourselves which would indicate deadlock.
- Add the proc lock to the witness dup_list as we may hold more than one
process lock at a time.
- Don't assert a mutex is owned in _mtx_unlock_sleep() as that is too late.
We do the checks in the macros instead.
mutex operations in kthread_create().
- Lock a kthread's proc before changing its parent via proc_reparent().
- Test P_KTHREAD not P_SYSTEM in kthread_suspend() and kthread_resume().
P_SYSTEM just means that the process shouldn't be swapped and is used
for vinum's daemon for example.
- Lock all the signal state used for suspending and resuming kthreads with
the proc lock.
- Add proc locking to fork1(). Always lock the child procoess (new
process) first when both processes need to be locked at the same
time.
- Remove unneeded spl()'s as the data they protected is now locked.
- Ensure that the proctree is exclusively locked and the new process is
locked when setting up the parent process pointer.
- Lock the check for P_KTHREAD in p_flag in fork_exit().
possible for us to see a process in the early stages of fork before p_fd
has been initialized. Ideally, we wouldn't stick a process on the allproc
list until it was fully created however.
than dinking around in the process lists explicitly.
- Hold both the proctree lock and proc lock of the child process when
reparenting a process via proc_reparent.
- Lock processes while sending them signals.
- Miscellaenous proc locking.
- proc_reparent() now asserts that the child is locked in addition to an
exclusive proctree lock.
INVARIANTS case, define the actual KASSERT() in _SX_ASSERT_[SX]LOCKED
macros that are used in the sx code itself and convert the
SX_ASSERT_[SX]LOCKED macros to simple wrappers that grab the mutex for the
duration of the check.
support implementations of ACLs in file systems. Introduce the
following new functions:
vaccess_acl_posix1e() vaccess() that accepts an ACL
acl_posix1e_mode_to_perm() Convert mode bits to ACL rights
acl_posix1e_mode_to_entry() Build ACL entry from mode/uid/gid
acl_posix1e_perms_to_mode() Generate file mode from ACL
acl_posix1e_check() Syntax verification for ACL
These functions allow a file system to rely on central ACL evaluation
and syntax checking, as well as providing useful utilities to
allow ACL-based file systems to generate mode/owner/etc information
to return via VOP_GETATTR(), and to support file systems that split
their ACL information over their existing inode storage (mode, uid,
gid) and extended ACL into extended attributes (additional users,
groups, ACL mask).
o Add prototypes for exported functions to sys/acl.h, sys/vnode.h
Reviewed by: trustedbsd-discuss, freebsd-arch
Obtained from: TrustedBSD Project
but potentially significant in -4.x.)
Eliminate a pointless parameter to aio_fphysio().
Remove unnecessary casts from aio_fphysio() and aio_physwakeup().
- Add sx_xholder member to sx struct which is used for INVARIANTS-enabled
assertions. It indicates the thread that presently owns the xlock.
- Add some assertions to the sx lock code that will detect the fatal
API abuse:
xlock --> xlock
xlock --> slock
which now works thanks to sx_xholder.
Notice that the remaining two problematic cases:
slock --> xlock
slock --> slock (a little less problematic, but still recursion)
will need to be handled by witness eventually, as they are more
involved.
Reviewed by: jhb, jake, jasone
aiocb's allocated by zalloc(). In other words, zfree() was never
called. Now, we call zfree(). Why eliminate this micro-
optimization? At some later point, when we multithread the AIO
system, we would need a mutex to synchronize access to aio_freejobs,
making its use nearly indistinguishable in cost from zalloc() and
zfree().
Remove unnecessary fhold() and fdrop() calls from aio_qphysio(),
undo'ing a part of revision 1.86. The reference count on the file
structure is already incremented by _aio_aqueue() before it calls
aio_qphysio(). (Update the comments to document this fact.)
Remove unnecessary casts from _aio_aqueue(), aio_read(), aio_write()
and aio_waitcomplete().
Remove an unnecessary "return;" from aio_process().
Add "static" in various places.
related code from aio_read() and aio_write(). This field was
intended, but never used, to allow a mythical user-level library to
make an aio_read() or aio_write() behave like an ordinary read() or
write(), i.e., a blocking I/O operation.
- Add a KASSERT() to ensure an ithread has a backing kernel thread when we
schedule it.
- Don't attempt to preemptively switch to an ithread if p_stat of curproc
is not SRUN.
An initial tidyup of the mount() syscall and VFS mount code.
This code replaces the earlier work done by jlemon in an attempt to
make linux_mount() work.
* the guts of the mount work has been moved into vfs_mount().
* move `type', `path' and `flags' from being userland variables into being
kernel variables in vfs_mount(). `data' remains a pointer into
userspace.
* Attempt to verify the `type' and `path' strings passed to vfs_mount()
aren't too long.
* rework mount() and linux_mount() to take the userland parameters
(besides data, as mentioned) and pass kernel variables to vfs_mount().
(linux_mount() already did this, I've just tidied it up a little more.)
* remove the copyin*() stuff for `path'. `data' still requires copyin*()
since its a pointer into userland.
* set `mount->mnt_statf_mntonname' in vfs_mount() rather than in each
filesystem. This variable is generally initialised with `path', and
each filesystem can override it if they want to.
* NOTE: f_mntonname is intiailised with "/" in the case of a root mount.
`rootvnode' pointer, but vfs_syscalls.c's checkdirs() assumed that
it did. This bug reliably caused a panic at reboot time if any
filesystem had been mounted directly over /.
The checkdirs() function is called at mount time to find any process
fd_cdir or fd_rdir pointers referencing the covered mountpoint
vnode. It transfers these to point at the root of the new filesystem.
However, this process was not reversed at unmount time, so processes
with a cwd/root at a mount point would unexpectedly lose their
cwd/root following a mount-unmount cycle at that mountpoint.
This change should fix both of the above issues. Start_init() now
holds an extra vnode reference corresponding to `rootvnode', and
dounmount() releases this reference when the root filesystem is
unmounted just before reboot. Dounmount() now undoes the actions
taken by checkdirs() at mount time; any process cdir/rdir pointers
that reference the root vnode of the unmounted filesystem are
transferred to the now-uncovered vnode.
Reviewed by: bde, phk
hit on the client side and prevent the server side from retiring writes.
Pipeline operations turned off for all READs (no big loss since reads are
usually synchronous) and for NFS writes, and left on for the default bwrite().
(MFC expected prior to 4.3 freeze)
Testing by: mjacob, dillon
update native priority, it is diffcult to get right and likely
to end up horribly wrong. Use an honestly wrong fixed value
that seems to work; PUSER for user threads, and the interrupt
priority for ithreads. Set it once when the process is created
and forget about it.
Suggested by: bde
Pointy hat: me
process's priority go through the roof when it released a (contested)
mutex. Only set the native priority in mtx_lock if hasn't already
been set.
Reviewed by: jhb
