Commit Graph

4 Commits

Author SHA1 Message Date
adrian
8e4ce17ba2 Remove duplicate txflags field from ath_buf.
rename bf_state.bfs_flags to bf_state.bfs_txflags, as that is what
it effectively is.
2012-04-07 02:01:26 +00:00
adrian
f4dc64af6e Delay sequence number allocation for A-MPDU until just before the frame
is queued to the hardware.

Because multiple concurrent paths can execute ath_start(), multiple
concurrent paths can push frames into the software/hardware TX queue
and since preemption/interrupting can occur, there's the possibility
that a gap in time will occur between allocating the sequence number
and queuing it to the hardware.

Because of this, it's possible that a thread will have allocated a
sequence number and then be preempted by another thread doing the same.
If the second thread sneaks the frame into the BAW, the (earlier) sequence
number of the first frame will be now outside the BAW and will result
in the frame being constantly re-added to the tail of the queue.
There it will live until the sequence numbers cycle around again.

This also creates a hole in the RX BAW tracking which can also cause
issues.

This patch delays the sequence number allocation to occur only just before
the frame is going to be added to the BAW.  I've been wanting to do this
anyway as part of a general code tidyup but I've not gotten around to it.
This fixes the PR.

However, it still makes it quite difficult to try and ensure in-order
queuing and dequeuing of frames. Since multiple copies of ath_start()
can be run at the same time (eg one TXing process thread, one TX completion
task/one RX task) the driver may end up having frames dequeued and pushed
into the hardware slightly/occasionally out of order.

And, to make matters more annoying, net80211 may have the same behaviour -
in the non-aggregation case, the TX code allocates sequence numbers
before it's thrown to the driver.  I'll open another PR to investigate
this and potentially introduce some kind of final-pass TX serialisation
before frames are thrown to the hardware.  It's also very likely worthwhile
adding some debugging code into ath(4) and net80211 to catch when/if this
does occur.

PR:		kern/166190
2012-03-20 04:50:25 +00:00
adrian
d1f6843e2d Add support to the TX descriptor printing code to follow ath_buf
chains. This allows for debugging of aggregate frames.

Sponsored by:	Hobnob, Inc.
2011-11-08 22:01:03 +00:00
adrian
bb5c10096e Break out the debug macros from if_ath.c into if_ath_debug.[ch] .
This is prep work for breaking out the TX path into a separate
set of source files.
2011-01-29 05:08:21 +00:00