PIPE_MTX().
Since the pipe_present is cleared before (potentially) sleeping, the
second thread may enter the pipeclose() for the reciprocal pipe end.
The test at the end of the pipeclose() for the pipe_present == 0 would
succeed, allowing the second thread to free the pipe memory. First
threads then accesses the freed memory after being woken up.
Properly track the closing state of the pipe in the pipe_present.
Introduce the intermediate state that marks the pipe as mostly
dismantled but might be sleeping waiting for the knote list to be
cleared. Free the pipe pair memory only when both ends pass that point.
Debugging help and tested by: pho
Discussed with: jmg
MFC after: 2 weeks
monitoring the pipe. The code sets pipe_present = 0 and enters
knlist_cleardel(), where the PIPE_MTX might be dropped when knl->kl_list
cannot be cleared due to influx knotes.
If the following often encountered code fragment
if (!(kn->kn_status & KN_DETACHED))
kn->kn_fop->f_detach(kn);
knote_drop(kn, td); [1]
is executed while the knlist lock is dropped, then the knote memory is freed
by the knote_drop() without knote being removed from the knlist, since
the filt_pipedetach() contains the following:
if (kn->kn_filter == EVFILT_WRITE) {
if (!cpipe->pipe_peer->pipe_present) {
PIPE_UNLOCK(cpipe);
return;
Now, the memory may be reused in the zone, causing the access to the
freed memory. I got the panics caused by the marker knote appearing on
the knlist, that, I believe, manifestation of the issue. In the Peter
Holm test scenarious, we got unkillable processes too.
The pipe_peer that has the knote for write shall be present. Ignore the
pipe_present value for EVFILT_WRITE in filt_pipedetach().
Debugging help and tested by: pho
Discussed with: jmg
MFC after: 2 weeks
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
details from consumers.
- Track individual selecters on a per-descriptor basis such that there
are no longer collisions and after sleeping for events only those
descriptors which triggered events must be rescaned.
- Protect the selinfo (per descriptor) structure with a mtx pool mutex.
mtx pool mutexes were chosen to preserve api compatibility with
existing code which does nothing but bzero() to setup selinfo
structures.
- Use a per-thread wait channel rather than a global wait channel.
- Hide select implementation details in a seltd structure which is
opaque to the rest of the kernel.
- Provide a 'selsocket' interface for those kernel consumers who wish to
select on a socket when they have no fd so they no longer have to
be aware of select implementation details.
Tested by: kris
Reviewed on: arch
o buffered write, for chunks smaller than PIPE_MINDIRECT bytes
o direct write, for everything else
A call to writev(2) may receive struct iov of various size and the
kernel may have to switch from one solution to the other. Before doing
this, it must wake reader processes and any select/poll/kqueue up.
This commit fixes a bug where select/poll/kqueue are not triggered
when switching from buffered write to direct write. It adds calls to
pipeselwakeup().
I give more details on freebsd-arch@:
http://lists.freebsd.org/pipermail/freebsd-arch/2007-September/006790.html
This should fix issues with Erlang (lang/erlang) and kqueue.
Reported by: Rickard Green (Erlang)
from Mac OS X Leopard--rationalize naming for entry points to
the following general forms:
mac_<object>_<method/action>
mac_<object>_check_<method/action>
The previous naming scheme was inconsistent and mostly
reversed from the new scheme. Also, make object types more
consistent and remove spaces from object types that contain
multiple parts ("posix_sem" -> "posixsem") to make mechanical
parsing easier. Introduce a new "netinet" object type for
certain IPv4/IPv6-related methods. Also simplify, slightly,
some entry point names.
All MAC policy modules will need to be recompiled, and modules
not updates as part of this commit will need to be modified to
conform to the new KPI.
Sponsored by: SPARTA (original patches against Mac OS X)
Obtained from: TrustedBSD Project, Apple Computer
existing UMA statistics for pipes, and allows us to get rid of both the
per-pipe dtor and two atomic operations per pipe required to maintain
the counter.
- Remove also "MP SAFE" after prior "MPSAFE" pass. (suggested by bde)
- Remove extra blank lines in some cases.
- Add extra blank lines in some cases.
- Remove no-op comments consisting solely of the function name, the word
"syscall", or the system call name.
- Add punctuation.
- Re-wrap some comments.
begun with a repo-copy of mac.h to mac_framework.h. sys/mac.h now
contains the userspace and user<->kernel API and definitions, with all
in-kernel interfaces moved to mac_framework.h, which is now included
across most of the kernel instead.
This change is the first step in a larger cleanup and sweep of MAC
Framework interfaces in the kernel, and will not be MFC'd.
Obtained from: TrustedBSD Project
Sponsored by: SPARTA
- Move sonewconn(), which creates new sockets for incoming connections on
listen sockets, so that all socket allocate code is together in
uipc_socket.c.
- Move 'maxsockets' and associated sysctls to uipc_socket.c with the
socket allocation code.
- Move kern.ipc sysctl node to uipc_socket.c, add a SYSCTL_DECL() for it
to sysctl.h and remove lots of scattered implementations in various
IPC modules.
- Sort sodealloc() after soalloc() in uipc_socket.c for dependency order
reasons. Statisticize soalloc() and sodealloc() as they are now
required only in uipc_socket.c, and are internal to the socket
implementation.
After this change, socket allocation and deallocation is entirely
centralized in one file, and uipc_socket2.c consists entirely of socket
buffer manipulation and default protocol switch functions.
MFC after: 1 month
- Introducing the possibility of using locks different than mutexes
for the knlist locking. In order to do this, we add three arguments to
knlist_init() to specify the functions to use to lock, unlock and
check if the lock is owned. If these arguments are NULL, we assume
mtx_lock, mtx_unlock and mtx_owned, respectively.
- Using the vnode lock for the knlist locking, when doing kqueue operations
on a vnode. This way, we don't have to lock the vnode while holding a
mutex, in filt_vfsread.
Reviewed by: jmg
Approved by: re (scottl), scottl (mentor override)
Pointyhat to: ssouhlal
Will be happy: everyone
they both happen before pipe backing allocation occurs. Previously,
a pipe memory shortage would cause a panic due to a KNOTE call
on an uninitialized si_note.
Reported by: Peter Holm
MFC after: 1 week
release the pipe mutex before calling fsetown(), as fsetown()
may block. The sigio code protects the pipe sigio data using
its own mutex, and the pipe reference count held by the caller
will prevent the pipe from being prematurely garbage-collected.
Discovered by: imp
- pipespace is now able to resize non-empty pipes; this allows
for many more resizing opportunities
- Backing is no longer pre-allocated for the reverse direction
of pipes. This direction is rarely (if ever) used, so this cuts the
amount of map space allocated to a pipe in half.
- Pipe growth is now much more dynamic; a pipe will now grow when
the total amount of data it contains and the size of the write are
larger than the size of pipe. Previously, only individual writes greater
than the size of the pipe would cause growth.
- In low memory situations, pipes will now shrink during both read
and write operations, where possible. Once the memory shortage
ends, the growth code will cause these pipes to grow back to an appropriate
size.
- If the full PIPE_SIZE allocation fails when a new pipe is created, the
allocation will be retried with SMALL_PIPE_SIZE. This helps to deal
with the situation of a fragmented map after a low memory period has
ended.
- Minor documentation + code changes to support the above.
In total, these changes increase the total number of pipes that
can be allocated simultaneously, drastically reducing the chances that
pipe allocation will fail.
Performance appears unchanged due to dynamic resizing.
a more complete subsystem, and removes the knowlege of how things are
implemented from the drivers. Include locking around filter ops, so a
module like aio will know when not to be unloaded if there are outstanding
knotes using it's filter ops.
Currently, it uses the MTX_DUPOK even though it is not always safe to
aquire duplicate locks. Witness currently doesn't support the ability
to discover if a dup lock is ok (in some cases).
Reviewed by: green, rwatson (both earlier versions)
pipelock(), not via a mixture of mutexes and pipelock(). Additionally,
add a few KASSERTS, and change some statements that should have been
KASSERTS into KASSERTS.
As a result of these cleanups, some segments of code have become
significantly shorter and/or easier to read.
so that they know whether the allocation is supposed to be able to sleep
or not.
* Allow uma_zone constructors and initialation functions to return either
success or error. Almost all of the ones in the tree currently return
success unconditionally, but mbuf is a notable exception: the packet
zone constructor wants to be able to fail if it cannot suballocate an
mbuf cluster, and the mbuf allocators want to be able to fail in general
in a MAC kernel if the MAC mbuf initializer fails. This fixes the
panics people are seeing when they run out of memory for mbuf clusters.
* Allow debug.nosleepwithlocks on WITNESS to be disabled, without changing
the default.
Both bmilekic and jeff have reviewed the changes made to make failable
zone allocations work.
can't yet be referenced by other threads.
In microbenchmarks, this appears to reduce the cost of
pipe();close();close() on UP by 10%, and SMP by 7%. The vast majority
of the cost of allocating a pipe remains VM magic.
Suggested by: silby
instead of ephemeral mappings using pmap_qenter() by the writer. The
writer is still, however, responsible for wiring the pages, just not
mapping them. Consequently, the allocation of KVA for the direct case is
unnecessary. Remove it and the sysctls limiting it, i.e.,
kern.ipc.maxpipekvawired and kern.ipc.amountpipekvawired. The number
of temporarily wired pages is still, however, limited by
kern.ipc.maxpipekva.
Note: On platforms lacking a direct virtual-to-physical mapping,
uiomove_fromphys() uses sf_bufs to cache ephemeral mappings. Thus,
the number of available sf_bufs can influence the performance of pipes
on platforms such i386. Surprisingly, I saw the greatest gain from this
change on such a machine: lmbench's pipe bandwidth result increased from
~1050MB/s to ~1850MB/s on my 2.4GHz, 400MHz FSB P4 Xeon.
of all, PIPE_EOF is not checked pervasively after everything that can drop
the pipe mutex and msleep(), so fix. Additionally, though it might not
harm anything, pipelock() and pipeunlock() are not used consistently.
Third, the kqueue support functions do not use the pipe mutex correctly.
Last, but absolutely not least, is a race: if pipe_busy is not set on
the closing side of the pipe, the other side that is trying to write to
that will crash BECAUSE PIPE_EOF IS NOT SET! Unconditionally set
PIPE_EOF, and get rid of all the lockups/crashes I have seen trying
to build ports.
instead, just dec/inc in the ctor/dtor. For now, increment/decrement
in two's, since we're now performing the operation once per pair,
not once per pipe. Not really any measurable performance change
in my micro-benchmarks, but doing less work is good, especially when
it comes to atomic operations.
Suggested by: alc
changes to jointly allocated pipe pairs. Replace these checks
with pipe_present checks. This avoids a NULL pointer dereference
when a pipe is half-closed.
Submitted by: Peter Edwards <peter.edwards@openet-telecom.com>
would allocate two 'struct pipe's from the pipe zone, and malloc a
mutex.
- Create a new "struct pipepair" object holding the two 'struct
pipe' instances, struct mutex, and struct label reference. Pipe
structures now have a back-pointer to the pipe pair, and a
'pipe_present' flag to indicate whether the half has been
closed.
- Perform mutex init/destroy in zone init/destroy, avoiding
reallocating the mutex for each pipe. Perform most pipe structure
setup in zone constructor.
- VM memory mappings for pageable buffers are still done outside of
the UMA zone.
- Change MAC API to speak 'struct pipepair' instead of 'struct pipe',
update many policies. MAC labels are also handled outside of the
UMA zone for now. Label-only policy modules don't have to be
recompiled, but if a module is recompiled, its pipe entry points
will need to be updated. If a module actually reached into the
pipe structures (unlikely), that would also need to be modified.
These changes substantially simplify failure handling in the pipe
code as there are many fewer possible failure modes.
On half-close, pipes no longer free the 'struct pipe' for the closed
half until a full-close takes place. However, VM mapped buffers
are still released on half-close.
Some code refactoring is now possible to clean up some of the back
references, etc; this patch attempts not to change the structure
of most of the pipe implementation, only allocation/free code
paths, so as to avoid introducing bugs (hopefully).
This cuts about 8%-9% off the cost of sequential pipe allocation
and free in system call tests on UP and SMP in my micro-benchmarks.
May or may not make a difference in macro-benchmarks, but doing
less work is good.
Reviewed by: juli, tjr
Testing help: dwhite, fenestro, scottl, et al
in OpenBSD by Niels Provos. The patch introduces a bitmap of allocated
file descriptors which is used to locate available descriptors when a new
one is needed. It also moves the task of growing the file descriptor table
out of fdalloc(), reducing complexity in both fdalloc() and do_dup().
Debts of gratitude are owed to tjr@ (who provided the original patch on
which this work is based), grog@ (for the gdb(4) man page) and rwatson@
(for assistance with pxeboot(8)).
thread being waken up. The thread waken up can run at a priority as
high as after tsleep().
- Replace selwakeup()s with selwakeuppri()s and pass appropriate
priorities.
- Add cv_broadcastpri() which raises the priority of the broadcast
threads. Used by selwakeuppri() if collision occurs.
Not objected in: -arch, -current
Instead, let the vm objects be lazily instantiated at fault time. This
results in the allocation of fewer vm objects and vm map entries due to
aggregation in the vm system.
table, acquiring the necessary locks as it works. It usually returns
two references to the new descriptor: one in the descriptor table
and one via a pointer argument.
As falloc releases the FILEDESC lock before returning, there is a
potential for a process to close the reference in the file descriptor
table before falloc's caller gets to use the file. I don't think this
can happen in practice at the moment, because Giant indirectly protects
closes.
To stop the file being completly closed in this situation, this change
makes falloc set the refcount to two when both references are returned.
This makes life easier for several of falloc's callers, because the
first thing they previously did was grab an extra reference on the
file.
Reviewed by: iedowse
Idea run past: jhb
kqueue write events on a socket and you regularly create tons of pipes
which overwrites the structure causing a panic when removing the knote
from the list. If the peer has gone away (and it's a write knote), then
don't bother trying to remove the knote from the list.
Submitted by: Brian Buchanan and myself
Obtained from: nCircle
From alc:
Move pageable pipe memory to a seperate kernel submap to avoid awkward
vm map interlocking issues. (Bad explanation provided by me.)
From me:
Rework pipespace accounting code to handle this new layout, and adjust
our default values to account for the fact that we now have a solid
limit on allocations.
Also, remove the "maxpipes" limit, as it no longer has a purpose.
(The limit on kva usage solves the problem of having two many pipes.)
application could cause a wired page to be freed. In general,
vm_page_hold() should be preferred for ephemeral kernel mappings of pages
borrowed from a user-level address space. (vm_page_wire() should really be
reserved for indefinite duration pinning by the "owner" of the page.)
Discussed with: silby
Submitted by: tegge
on a non-blocking pipe in cases where select(2) returns the file
descriptor as ready for write. This in turns causes libc_r, for
one, to busy wait in such cases.
Note: it is a quick performance fix, a more complex fix might be
required in case this turns out to have unexpected side effects.
Reviewed by: silby
MFC after: 3 days
a long-standing mistake in the way a portion of a pipe's KVA is
allocated. Specifically, kmem_alloc_pageable() is inappropriate
for use in the "direct" case because it allows a preceding vm map entry
and vm object to be extended to support the new KVA allocation.
However, the direct case KVA allocation should not have a backing
vm object. This is corrected by using kmem_alloc_nofault().
Submitted by: tegge (with the above explanation by me)
- Use atomic ops to update the bigpipe count
- Make the bigpipe count sysctl readable
- Remove a duplicate comparison in an if statement
- Comment two SYSCTLs.
- Limit the total number of pipes so that we do not
exhaust all vm objects in the kernel map. When
this limit is reached, a ratelimited message will
be printed to the console.
- Put a soft limit on the amount of memory consumable
by pipes. Once the limit has been reached, all new
pipes will be limited to 4K in size, rather than the
default of 16K.
- Put a limit on the number of pages that may be used
for high speed page flipping in order to reduce the
amount of wired memory. Pipe writes that occur
while this limit is exceeded will fall back to
non-page flipping mode.
The above values are auto-tuned in subr_param.c and
are scaled to take into account both the size of
physical memory and the size of the kernel map.
These limits help to reduce the "kernel resources exhausted"
panics that could be caused by opening a large
number of pipes. (Pipes alone are no longer able
to exhaust all resources, but other kernel memory hogs
in league with pipes may still be able to do so.)
PR: 53627
Ideas / comments from: hsu, tjr, dillon@apollo.backplane.com
MFC after: 1 week
where physical addresses larger than virtual addresses, such as i386s
with PAE.
- Use this to represent physical addresses in the MI vm system and in the
i386 pmap code. This also changes the paddr parameter to d_mmap_t.
- Fix printf formats to handle physical addresses >4G in the i386 memory
detection code, and due to kvtop returning vm_paddr_t instead of u_long.
Note that this is a name change only; vm_paddr_t is still the same as
vm_offset_t on all currently supported platforms.
Sponsored by: DARPA, Network Associates Laboratories
Discussed with: re, phk (cdevsw change)
pointer types, and remove a huge number of casts from code using it.
Change struct xfile xf_data to xun_data (ABI is still compatible).
If we need to add a #define for f_data and xf_data we can, but I don't
think it will be necessary. There are no operational changes in this
commit.
It must be removed because it is done without the pipe being locked
via pipelock() and therefore is vulnerable to races with pipespace()
erroneously triggering it by temporarily zero'ing out the structure
backing the pipe.
It looks as if this assertion is not needed because all manipulation
of the data changed by pipespace() _is_ protected by pipelock().
Reported by: kris, mckusick
dereference the struct sigio pointer without any locking. Change
fgetown() to take a reference to the pointer instead of a copy of the
pointer and call SIGIO_LOCK() before copying the pointer and
dereferencing it.
Reviewed by: rwatson
(1) Where previously the pipe mutex was selectively grabbed during
pipe_ioctl(), now always grab it and then release if if not
needed. This protects the call to mac_check_pipe_ioctl() to
make sure the label remains consistent. (Note: it looks
like sigio locking may be incorrect for fgetown() since we
call it not-by-reference and sigio locking assumes call by
reference).
(2) In pipe_stat(), lock the pipe if MAC is compiled in so that
the call to mac_check_pipe_stat() gets a locked pipe to
protect label consistency. We still release the lock before
returning actual stat() data, risking inconsistency, but
apparently our pipe locking model accepts that risk.
(3) In various pipe MAC authorization checks, assert that the pipe
lock is held.
(4) Grab the lock when performing a pipe relabel operation, and
assert it a little deeper in the stack.
Obtained from: TrustedBSD Project
Sponsored by: DARPA, Network Associates Laboratories
mac_check_pipe_poll(), mac_check_pipe_read(), mac_check_pipe_stat(),
and mac_check_pipe_write(). This is improves consistency with other
access control entry points and permits security modules to only
control the object methods that they are interested in, avoiding
switch statements.
Obtained from: TrustedBSD Project
Sponsored by: DARPA, NAI Labs
accept an 'active_cred' argument reflecting the credential of the thread
initiating the ioctl operation.
- Change fo_ioctl() to accept active_cred; change consumers of the
fo_ioctl() interface to generally pass active_cred from td->td_ucred.
- In fifofs, initialize filetmp.f_cred to ap->a_cred so that the
invocations of soo_ioctl() are provided access to the calling f_cred.
Pass ap->a_td->td_ucred as the active_cred, but note that this is
required because we don't yet distinguish file_cred and active_cred
in invoking VOP's.
- Update kqueue_ioctl() for its new argument.
- Update pipe_ioctl() for its new argument, pass active_cred rather
than td_ucred to MAC for authorization.
- Update soo_ioctl() for its new argument.
- Update vn_ioctl() for its new argument, use active_cred rather than
td->td_ucred to authorize VOP_IOCTL() and the associated VOP_GETATTR().
Obtained from: TrustedBSD Project
Sponsored by: DARPA, NAI Labs
fo_read() and fo_write(): explicitly use the cred argument to fo_poll()
as "active_cred" using the passed file descriptor's f_cred reference
to provide access to the file credential. Add an active_cred
argument to fo_stat() so that implementers have access to the active
credential as well as the file credential. Generally modify callers
of fo_stat() to pass in td->td_ucred rather than fp->f_cred, which
was redundantly provided via the fp argument. This set of modifications
also permits threads to perform these operations on behalf of another
thread without modifying their credential.
Trickle this change down into fo_stat/poll() implementations:
- badfo_poll(), badfo_stat(): modify/add arguments.
- kqueue_poll(), kqueue_stat(): modify arguments.
- pipe_poll(), pipe_stat(): modify/add arguments, pass active_cred to
MAC checks rather than td->td_ucred.
- soo_poll(), soo_stat(): modify/add arguments, pass fp->f_cred rather
than cred to pru_sopoll() to maintain current semantics.
- sopoll(): moidfy arguments.
- vn_poll(), vn_statfile(): modify/add arguments, pass new arguments
to vn_stat(). Pass active_cred to MAC and fp->f_cred to VOP_POLL()
to maintian current semantics.
- vn_close(): rename cred to file_cred to reflect reality while I'm here.
- vn_stat(): Add active_cred and file_cred arguments to vn_stat()
and consumers so that this distinction is maintained at the VFS
as well as 'struct file' layer. Pass active_cred instead of
td->td_ucred to MAC and to VOP_GETATTR() to maintain current semantics.
- fifofs: modify the creation of a "filetemp" so that the file
credential is properly initialized and can be used in the socket
code if desired. Pass ap->a_td->td_ucred as the active
credential to soo_poll(). If we teach the vnop interface about
the distinction between file and active credentials, we would use
the active credential here.
Note that current inconsistent passing of active_cred vs. file_cred to
VOP's is maintained. It's not clear why GETATTR would be authorized
using active_cred while POLL would be authorized using file_cred at
the file system level.
Obtained from: TrustedBSD Project
Sponsored by: DARPA, NAI Labs
make a series of modifications to the credential arguments relating
to file read and write operations to cliarfy which credential is
used for what:
- Change fo_read() and fo_write() to accept "active_cred" instead of
"cred", and change the semantics of consumers of fo_read() and
fo_write() to pass the active credential of the thread requesting
an operation rather than the cached file cred. The cached file
cred is still available in fo_read() and fo_write() consumers
via fp->f_cred. These changes largely in sys_generic.c.
For each implementation of fo_read() and fo_write(), update cred
usage to reflect this change and maintain current semantics:
- badfo_readwrite() unchanged
- kqueue_read/write() unchanged
pipe_read/write() now authorize MAC using active_cred rather
than td->td_ucred
- soo_read/write() unchanged
- vn_read/write() now authorize MAC using active_cred but
VOP_READ/WRITE() with fp->f_cred
Modify vn_rdwr() to accept two credential arguments instead of a
single credential: active_cred and file_cred. Use active_cred
for MAC authorization, and select a credential for use in
VOP_READ/WRITE() based on whether file_cred is NULL or not. If
file_cred is provided, authorize the VOP using that cred,
otherwise the active credential, matching current semantics.
Modify current vn_rdwr() consumers to pass a file_cred if used
in the context of a struct file, and to always pass active_cred.
When vn_rdwr() is used without a file_cred, pass NOCRED.
These changes should maintain current semantics for read/write,
but avoid a redundant passing of fp->f_cred, as well as making
it more clear what the origin of each credential is in file
descriptor read/write operations.
Follow-up commits will make similar changes to other file descriptor
operations, and modify the MAC framework to pass both credentials
to MAC policy modules so they can implement either semantic for
revocation.
Obtained from: TrustedBSD Project
Sponsored by: DARPA, NAI Labs
as part of the TrustedBSD MAC framework. Instrument the creation
and destruction of pipes, as well as relevant operations, with
necessary calls to the MAC framework. Note that the locking
here is probably not quite right yet, but fixes will be forthcoming.
Obtained from: TrustedBSD Project
Sponsored by: DARPA, NAI Labs
be done internally.
Ensure that no one can fsetown() to a dying process/pgrp. We need
to check the process for P_WEXIT to see if it's exiting. Process
groups are already safe because there is no such thing as a pgrp
zombie, therefore the proctree lock completely protects the pgrp
from having sigio structures associated with it after it runs
funsetownlst.
Add sigio lock to witness list under proctree and allproc, but over
proc and pgrp.
Seigo Tanimura helped with this.
Turn the sigio sx into a mutex.
Sigio lock is really only needed to protect interrupts from dereferencing
the sigio pointer in an object when the sigio itself is being destroyed.
In order to do this in the most unintrusive manner change pgsigio's
sigio * argument into a **, that way we can lock internally to the
function.
belong to a user virtual address; while this happens to work on some
architectures, it can't on sparc64, since user and kernel virtual
address spaces overlap there (the distinction between them is done via
separate address space identifiers).
Instead, look up the page in the vm_map of the process in question.
Reviewed by: jake
most cases NULL is passed, but in some cases such as network driver locks
(which use the MTX_NETWORK_LOCK macro) and UMA zone locks, a name is used.
Tested on: i386, alpha, sparc64
can be called both with and without the pipe mutex held. (For example,
if called by pipeselwakeup(), it is held. Whereas, if called by kqueue_scan(),
it is not.)
Reviewed by: alfred
