freebsd kernel with SKQ
5cda6006e4
This patchset implements a new TX lock, covering both the per-VAP (and thus per-node) TX locking and the serialisation through to the underlying physical device. This implements the hard requirement that frames to the underlying physical device are scheduled to the underlying device in the same order that they are processed at the VAP layer. This includes adding extra encapsulation state (such as sequence numbers and CCMP IV numbers.) Any order mismatch here will result in dropped packets at the receiver. There are multiple transmit contexts from the upper protocol layers as well as the "raw" interface via the management and BPF transmit paths. All of these need to be correctly serialised or bad behaviour will result under load. The specifics: * add a new TX IC lock - it will eventually just be used for serialisation to the underlying physical device but for now it's used for both the VAP encapsulation/serialisation and the physical device dispatch. This lock is specifically non-recursive. * Methodize the parent transmit, vap transmit and ic_raw_xmit function pointers; use lock assertions in the parent/vap transmit routines. * Add a lock assertion in ieee80211_encap() - the TX lock must be held here to guarantee sensible behaviour. * Refactor out the packet sending code from ieee80211_start() - now ieee80211_start() is just a loop over the ifnet queue and it dispatches each VAP packet send through ieee80211_start_pkt(). Yes, I will likely rename ieee80211_start_pkt() to something that better reflects its status as a VAP packet transmit path. More on that later. * Add locking around the management and BAR TX sending - to ensure that encapsulation and TX are done hand-in-hand. * Add locking in the mesh code - again, to ensure that encapsulation and mesh transmit are done hand-in-hand. * Add locking around the power save queue and ageq handling, when dispatching to the parent interface. * Add locking around the WDS handoff. * Add a note in the mesh dispatch code that the TX path needs to be re-thought-out - right now it's doing a direct parent device transmit rather than going via the vap layer. It may "work", but it's likely incorrect (as it bypasses any possible per-node power save and aggregation handling.) Why not a per-VAP or per-node lock? Because in order to ensure per-VAP ordering, we'd have to hold the VAP lock across parent->if_transmit(). There are a few problems with this: * There's some state being setup during each driver transmit - specifically, the encryption encap / CCMP IV setup. That should eventually be dragged back into the encapsulation phase but for now it lives in the driver TX path. This should be locked. * Two drivers (ath, iwn) re-use the node->ni_txseqs array in order to allocate sequence numbers when doing transmit aggregation. This should also be locked. * Drivers may have multiple frames queued already - so when one calls if_transmit(), it may end up dispatching multiple frames for different VAPs/nodes, each needing a different lock when handling that particular end destination. So to be "correct" locking-wise, we'd end up needing to grab a VAP or node lock inside the driver TX path when setting up crypto / AMPDU sequence numbers, and we may already _have_ a TX lock held - mostly for the same destination vap/node, but sometimes it'll be for others. That could lead to LORs and thus deadlocks. So for now, I'm sticking with an IC TX lock. It has the advantage of papering over the above and it also has the added advantage that I can assert that it's being held when doing a parent device transmit. I'll look at splitting the locks out a bit more later on. General outstanding net80211 TX path issues / TODO: * Look into separating out the VAP serialisation and the IC handoff. It's going to be tricky as parent->if_transmit() doesn't give me the opportunity to split queuing from driver dispatch. See above. * Work with monthadar to fix up the mesh transmit path so it doesn't go via the parent interface when retransmitting frames. * Push the encryption handling back into the driver, if it's at all architectually sane to do so. I know it's possible - it's what mac80211 in Linux does. * Make ieee80211_raw_xmit() queue a frame into VAP or parent queue rather than doing a short-cut direct into the driver. There are QoS issues here - you do want your management frames to be encapsulated and pushed onto the stack sooner than the (large, bursty) amount of data frames that are queued. But there has to be a saner way to do this. * Fragments are still broken - drivers need to be upgraded to an if_transmit() implementation and then fragmentation handling needs to be properly fixed. Tested: * STA - AR5416, AR9280, Intel 5300 abgn wifi * Hostap - AR5416, AR9160, AR9280 * Mesh - some testing by monthadar@, more to come. |
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| bin | ||
| cddl | ||
| contrib | ||
| crypto | ||
| etc | ||
| games | ||
| gnu | ||
| include | ||
| kerberos5 | ||
| lib | ||
| libexec | ||
| release | ||
| rescue | ||
| sbin | ||
| secure | ||
| share | ||
| sys | ||
| tools | ||
| usr.bin | ||
| usr.sbin | ||
| COPYRIGHT | ||
| LOCKS | ||
| MAINTAINERS | ||
| Makefile | ||
| Makefile.inc1 | ||
| ObsoleteFiles.inc | ||
| README | ||
| UPDATING | ||
This is the top level of the FreeBSD source directory. This file was last revised on: $FreeBSD$ For copyright information, please see the file COPYRIGHT in this directory (additional copyright information also exists for some sources in this tree - please see the specific source directories for more information). The Makefile in this directory supports a number of targets for building components (or all) of the FreeBSD source tree, the most commonly used one being ``world'', which rebuilds and installs everything in the FreeBSD system from the source tree except the kernel, the kernel-modules and the contents of /etc. The ``world'' target should only be used in cases where the source tree has not changed from the currently running version. See: http://www.freebsd.org/doc/en_US.ISO8859-1/books/handbook/makeworld.html for more information, including setting make(1) variables. The ``buildkernel'' and ``installkernel'' targets build and install the kernel and the modules (see below). Please see the top of the Makefile in this directory for more information on the standard build targets and compile-time flags. Building a kernel is a somewhat more involved process, documentation for which can be found at: http://www.freebsd.org/doc/en_US.ISO8859-1/books/handbook/kernelconfig.html And in the config(8) man page. Note: If you want to build and install the kernel with the ``buildkernel'' and ``installkernel'' targets, you might need to build world before. More information is available in the handbook. The sample kernel configuration files reside in the sys/<arch>/conf sub-directory (assuming that you've installed the kernel sources), the file named GENERIC being the one used to build your initial installation kernel. The file NOTES contains entries and documentation for all possible devices, not just those commonly used. It is the successor of the ancient LINT file, but in contrast to LINT, it is not buildable as a kernel but a pure reference and documentation file. Source Roadmap: --------------- bin System/user commands. cddl Various commands and libraries under the Common Development and Distribution License. contrib Packages contributed by 3rd parties. crypto Cryptography stuff (see crypto/README). etc Template files for /etc. games Amusements. gnu Various commands and libraries under the GNU Public License. Please see gnu/COPYING* for more information. include System include files. kerberos5 Kerberos5 (Heimdal) package. lib System libraries. libexec System daemons. release Release building Makefile & associated tools. rescue Build system for statically linked /rescue utilities. sbin System commands. secure Cryptographic libraries and commands. share Shared resources. sys Kernel sources. tools Utilities for regression testing and miscellaneous tasks. usr.bin User commands. usr.sbin System administration commands. For information on synchronizing your source tree with one or more of the FreeBSD Project's development branches, please see: http://www.freebsd.org/doc/en_US.ISO8859-1/books/handbook/synching.html