socket lock over pulling so_options and so_linger out of the socket
structure in order to retrieve a consistent snapshot. This may be
overkill if user space doesn't require a consistent snapshot.
resolved by socket locking: in particular, that we test the connection
state at the socket layer without locking, request that the protocol
begin listening, and then set the listen state on the socket
non-atomically, resulting in a non-atomic cross-layer test-and-set.
lock state. Convert tsleep() into msleep() with socket buffer mutex
as argument. Hold socket buffer lock over sbunlock() to protect sleep
lock state.
Assert socket buffer lock in sbwait() to protect the socket buffer
wait state. Convert tsleep() into msleep() with socket buffer mutex
as argument.
Modify sofree(), sosend(), and soreceive() to acquire SOCKBUF_LOCK()
in order to call into these functions with the lock, as well as to
start protecting other socket buffer use in their implementation. Drop
the socket buffer mutexes around calls into the protocol layer, around
potentially blocking operations, for copying to/from user space, and
VM operations relating to zero-copy. Assert the socket buffer mutex
strategically after code sections or at the beginning of loops. In
some cases, modify return code to ensure locks are properly dropped.
Convert the potentially blocking allocation of storage for the remote
address in soreceive() into a non-blocking allocation; we may wish to
move the allocation earlier so that it can block prior to acquisition
of the socket buffer lock.
Drop some spl use.
NOTE: Some races exist in the current structuring of sosend() and
soreceive(). This commit only merges basic socket locking in this
code; follow-up commits will close additional races. As merged,
these changes are not sufficient to run without Giant safely.
Reviewed by: juli, tjr
rwatson_netperf:
Introduce conditional locking of the socket buffer in fifofs kqueue
filters; KNOTE() will be called holding the socket buffer locks in
fifofs, but sometimes the kqueue() system call will poll using the
same entry point without holding the socket buffer lock.
Introduce conditional locking of the socket buffer in the socket
kqueue filters; KNOTE() will be called holding the socket buffer
locks in the socket code, but sometimes the kqueue() system call
will poll using the same entry points without holding the socket
buffer lock.
Simplify the logic in sodisconnect() since we no longer need spls.
NOTE: To remove conditional locking in the kqueue filters, it would
make sense to use a separate kqueue API entry into the socket/fifo
code when calling from the kqueue() system call.
- Lock down low hanging fruit use of sb_flags with socket buffer
lock.
- Lock down low hanging fruit use of so_state with socket lock.
- Lock down low hanging fruit use of so_options.
- Lock down low-hanging fruit use of sb_lowwat and sb_hiwat with
socket buffer lock.
- Annotate situations in which we unlock the socket lock and then
grab the receive socket buffer lock, which are currently actually
the same lock. Depending on how we want to play our cards, we
may want to coallesce these lock uses to reduce overhead.
- Convert a if()->panic() into a KASSERT relating to so_state in
soaccept().
- Remove a number of splnet()/splx() references.
More complex merging of socket and socket buffer locking to
follow.
flags relating to several aspects of socket functionality. This change
breaks out several bits relating to send and receive operation into a
new per-socket buffer field, sb_state, in order to facilitate locking.
This is required because, in order to provide more granular locking of
sockets, different state fields have different locking properties. The
following fields are moved to sb_state:
SS_CANTRCVMORE (so_state)
SS_CANTSENDMORE (so_state)
SS_RCVATMARK (so_state)
Rename respectively to:
SBS_CANTRCVMORE (so_rcv.sb_state)
SBS_CANTSENDMORE (so_snd.sb_state)
SBS_RCVATMARK (so_rcv.sb_state)
This facilitates locking by isolating fields to be located with other
identically locked fields, and permits greater granularity in socket
locking by avoiding storing fields with different locking semantics in
the same short (avoiding locking conflicts). In the future, we may
wish to coallesce sb_state and sb_flags; for the time being I leave
them separate and there is no additional memory overhead due to the
packing/alignment of shorts in the socket buffer structure.
reference count:
- Assert SOCK_LOCK(so) macros that directly manipulate so_count:
soref(), sorele().
- Assert SOCK_LOCK(so) in macros/functions that rely on the state of
so_count: sofree(), sotryfree().
- Acquire SOCK_LOCK(so) before calling these functions or macros in
various contexts in the stack, both at the socket and protocol
layers.
- In some cases, perform soisdisconnected() before sotryfree(), as
this could result in frobbing of a non-present socket if
sotryfree() actually frees the socket.
- Note that sofree()/sotryfree() will release the socket lock even if
they don't free the socket.
Submitted by: sam
Sponsored by: FreeBSD Foundation
Obtained from: BSD/OS
protect fields in the socket buffer. Add accessor macros to use the
mutex (SOCKBUF_*()). Initialize the mutex in soalloc(), and destroy
it in sodealloc(). Add addition, add SOCK_*() access macros which
will protect most remaining fields in the socket; for the time being,
use the receive socket buffer mutex to implement socket level locking
to reduce memory overhead.
Submitted by: sam
Sponosored by: FreeBSD Foundation
Obtained from: BSD/OS
global mutex, accept_mtx, which serializes access to the following
fields across all sockets:
so_qlen so_incqlen so_qstate
so_comp so_incomp so_list
so_head
While providing only coarse granularity, this approach avoids lock
order issues between sockets by avoiding ownership of the fields
by a specific socket and its per-socket mutexes.
While here, rewrite soclose(), sofree(), soaccept(), and
sonewconn() to add assertions, close additional races and address
lock order concerns. In particular:
- Reorganize the optimistic concurrency behavior in accept1() to
always allocate a file descriptor with falloc() so that if we do
find a socket, we don't have to encounter the "Oh, there wasn't
a socket" race that can occur if falloc() sleeps in the current
code, which broke inbound accept() ordering, not to mention
requiring backing out socket state changes in a way that raced
with the protocol level. We may want to add a lockless read of
the queue state if polling of empty queues proves to be important
to optimize.
- In accept1(), soref() the socket while holding the accept lock
so that the socket cannot be free'd in a race with the protocol
layer. Likewise in netgraph equivilents of the accept1() code.
- In sonewconn(), loop waiting for the queue to be small enough to
insert our new socket once we've committed to inserting it, or
races can occur that cause the incomplete socket queue to
overfill. In the previously implementation, it was sufficient
to simply tested once since calling soabort() didn't release
synchronization permitting another thread to insert a socket as
we discard a previous one.
- In soclose()/sofree()/et al, it is the responsibility of the
caller to remove a socket from the incomplete connection queue
before calling soabort(), which prevents soabort() from having
to walk into the accept socket to release the socket from its
queue, and avoids races when releasing the accept mutex to enter
soabort(), permitting soabort() to avoid lock ordering issues
with the caller.
- Generally cluster accept queue related operations together
throughout these functions in order to facilitate locking.
Annotate new locking in socketvar.h.
the socket is on an accept queue of a listen socket. This change
renames the flags to SQ_COMP and SQ_INCOMP, and moves them to a new
state field on the socket, so_qstate, as the locking for these flags
is substantially different for the locking on the remainder of the
flags in so_state.
them to behave the same as if the SS_NBIO socket flag had been set
for this call. The SS_NBIO flag for ordinary sockets is set by
fcntl(fd, F_SETFL, O_NONBLOCK).
Pass the MSG_NBIO flag to the soreceive() and sosend() calls in
fifo_read() and fifo_write() instead of frobbing the SS_NBIO flag
on the underlying socket for each I/O operation. The O_NONBLOCK
flag is a property of the descriptor, and unlike ordinary sockets,
fifos may be referenced by multiple descriptors.
mbuma is an Mbuf & Cluster allocator built on top of a number of
extensions to the UMA framework, all included herein.
Extensions to UMA worth noting:
- Better layering between slab <-> zone caches; introduce
Keg structure which splits off slab cache away from the
zone structure and allows multiple zones to be stacked
on top of a single Keg (single type of slab cache);
perhaps we should look into defining a subset API on
top of the Keg for special use by malloc(9),
for example.
- UMA_ZONE_REFCNT zones can now be added, and reference
counters automagically allocated for them within the end
of the associated slab structures. uma_find_refcnt()
does a kextract to fetch the slab struct reference from
the underlying page, and lookup the corresponding refcnt.
mbuma things worth noting:
- integrates mbuf & cluster allocations with extended UMA
and provides caches for commonly-allocated items; defines
several zones (two primary, one secondary) and two kegs.
- change up certain code paths that always used to do:
m_get() + m_clget() to instead just use m_getcl() and
try to take advantage of the newly defined secondary
Packet zone.
- netstat(1) and systat(1) quickly hacked up to do basic
stat reporting but additional stats work needs to be
done once some other details within UMA have been taken
care of and it becomes clearer to how stats will work
within the modified framework.
From the user perspective, one implication is that the
NMBCLUSTERS compile-time option is no longer used. The
maximum number of clusters is still capped off according
to maxusers, but it can be made unlimited by setting
the kern.ipc.nmbclusters boot-time tunable to zero.
Work should be done to write an appropriate sysctl
handler allowing dynamic tuning of kern.ipc.nmbclusters
at runtime.
Additional things worth noting/known issues (READ):
- One report of 'ips' (ServeRAID) driver acting really
slow in conjunction with mbuma. Need more data.
Latest report is that ips is equally sucking with
and without mbuma.
- Giant leak in NFS code sometimes occurs, can't
reproduce but currently analyzing; brueffer is
able to reproduce but THIS IS NOT an mbuma-specific
problem and currently occurs even WITHOUT mbuma.
- Issues in network locking: there is at least one
code path in the rip code where one or more locks
are acquired and we end up in m_prepend() with
M_WAITOK, which causes WITNESS to whine from within
UMA. Current temporary solution: force all UMA
allocations to be M_NOWAIT from within UMA for now
to avoid deadlocks unless WITNESS is defined and we
can determine with certainty that we're not holding
any locks when we're M_WAITOK.
- I've seen at least one weird socketbuffer empty-but-
mbuf-still-attached panic. I don't believe this
to be related to mbuma but please keep your eyes
open, turn on debugging, and capture crash dumps.
This change removes more code than it adds.
A paper is available detailing the change and considering
various performance issues, it was presented at BSDCan2004:
http://www.unixdaemons.com/~bmilekic/netbuf_bmilekic.pdf
Please read the paper for Future Work and implementation
details, as well as credits.
Testing and Debugging:
rwatson,
brueffer,
Ketrien I. Saihr-Kesenchedra,
...
Reviewed by: Lots of people (for different parts)
declaration. Observe that initialization in declaration is
frequently incompatible with locking, not just a bad idea
due to style(9).
Submitted by: bde
functions in kern_socket.c.
Rename the "canwait" field to "mflags" and pass M_WAITOK and M_NOWAIT
in from the caller context rather than "1" or "0".
Correct mflags pass into mac_init_socket() from previous commit to not
include M_ZERO.
Submitted by: sam
than a "waitok" argument. Callers now passing M_WAITOK or M_NOWAIT
rather than 0 or 1. This simplifies the soalloc() logic, and also
makes the waiting behavior of soalloc() more clear in the calling
context.
Submitted by: sam
at packet arrival.
For benchmarking purposes SO_BINTIME is preferable to SO_TIMEVAL
since it has higher resolution and lower overhead. Simultaneous
use of the two options is possible and they will return consistent
timestamps.
This introduces an extra test and a function call for SO_TIMEVAL, but I have
not been able to measure that.
sure to sooptcopyin() the (struct mac) so that the MAC Framework
knows which label types are being requested. This fixes process
queries of socket labels.
Obtained from: TrustedBSD Project
Sponsored by: DARPA, Network Associates Laboratories
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
do not clear the `sb_sel' member of the sockbuf structure
while invalidating the receive sockbuf in sorflush(), called
from soshutdown().
The panic was reproduceable from user land by attaching a knote
with EVFILT_READ filters to a socket, disabling further reads
from it using shutdown(2), and then closing it. knote_remove()
was called to remove all knotes from the socket file descriptor
by detaching each using its associated filterops' detach call-
back function, sordetach() in this case, which tried to remove
itself from the invalidated sockbuf's klist (sb_sel.si_note).
PR: kern/54331
SS_ISCONNECTING state, returning EINVAL (which is what POSIX mandates
in this case).
listen() on connected or connecting sockets would cause them to enter
a bad state; in the TCP case, this could cause sockets to go
catatonic or panics, depending on how the socket was connected.
Reviewed by: -net
MFC after: 2 weeks
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.
then call do_setopt_accept_filter(so, NULL) which will free the filter
instead of duplicating the code in do_setopt_accept_filter().
Pointed out by: Hiten Pandya <hiten@angelica.unixdaemons.com>
