On Thu, 9 Mar 2023 18:00:04 +0100 Alexander Wetzel <alexander@xxxxxxxxxxxxxx> wrote: > On 07.03.23 21:54, Alexander Wetzel wrote: > >>> > >> > >> I just uploaded a test patch to bugzilla. > >> Please have a look if that fixes the issue. > >> > >> If not I would be interested in the output of your iTXQ status. > >> Enable CONFIG_MAC80211_DEBUGFS and run this command when the > >> connection is bad and send/share/upload to bugzilla the resulting > >> debug.out: > >> > >> k=1; while [ $k -lt 10 ]; do \ > >> cat /sys/kernel/debug/ieee80211/phy?/netdev:*/stations/*/aqm; \ > >> k=$(($k+1)); done >> debug.out > > > > Thomas and I continued with some debugging in > > https://bugzilla.kernel.org/show_bug.cgi?id=217119 > > > > But the results so far are unexpected and we decided to continue > > the debugging with the round here. Hoping someone sees something I > > miss. > > > > A very summary where we are: > > I can't reproduce the bug with a very similar card and kernel > > config so far. Thomas card stops the iTXQs for intervalls >30s. > > Mine operates normally. > > > > A more useful but longer summary: > > > > Thomas updated to a 6.2 kernel and reported "connection drops and > > bandwidth problems" with his rt2800usb wlan card. (6.1 is ok.) > > Asked for some more details he reported: > > "...slow bandwidth stuff works better, but the main problem/test > > case is to start a 8-16 mbit video stream, which sometimes runs for > > a few seconds and then stops or it doesn't start at all" > > > > He bisected the issue and identified my commit 4444bc2116ae ("wifi: > > mac80211: Proper mark iTXQs for resumption") as culprit. > > > > Checking the internal iTXQ status when the issue is ongoing shows, > > that TID zero is flagged as dirty and thus is not transmitting > > queued packets. Interesting line from > > /sys/kernel/debug/ieee80211/phy?/netdev:*/stations/*/aqm: > > tid ac backlog-bytes backlog-packets new-flows drops marks > > overlimit collisions tx-bytes tx-packets flags > > 0 2 619736 404 1681 0 0 0 1 4513965 3019 0xe(RUN AMPDU NO-AMSDU > > DIRTY) > > --> The "normal" iTXQ handling IEEE80211_AC_BE has queued packets > > and is flagged as DIRTY. There even is a potential race setting the > > DIRTY flag, but the fix for that is not helping. > > > > Thus Thomas applied two debug patches, to better understand why the > > DIRTY flag is not cleared. > > > > And looking at the output from those we see that the driver stops > > Tx by calling ieee80211_stop_queue(). When ieee80211_wake_queue() > > mac80211 correctly resumes TX but is getting stopped by the driver > > after a single packet again. (The start of the relevant log is > > missing, so that may be initially more). > > I assume TX is still ok at that stage. But after some singe Tx > > operations the driver stops the queues again. Here the relevant > > part of the log: > > [ 179.584997] XXXX __ieee80211_wake_txqs: waking TID 0 > > [ 179.585022] XXXX drv_tx: TX > > [ 179.585027] XXXX ieee80211_stop_queue: called > > [ 179.585028] XXXX ieee80211_tx_dequeue: mark TID 0 dirty. Reason: > > 1 [ 179.585030] XXXX __ieee80211_wake_txqs: TID 3 NOT dirty > > [ 179.585031] XXXX __ieee80211_wake_txqs: TID 8 NOT dirty > > [ 179.585033] XXXX __ieee80211_wake_txqs: TID 11 NOT dirty > > [ 179.585034] XXXX __ieee80211_wake_txqs: EXIT > > [ 179.585035] XXXX __ieee80211_wake_txqs: ENTRY > > [ 179.585036] XXXX __ieee80211_wake_txqs: TID 1 NOT dirty > > [ 179.585037] XXXX __ieee80211_wake_txqs: TID 2 NOT dirty > > [ 179.585038] XXXX __ieee80211_wake_txqs: TID 9 NOT dirty > > [ 179.585040] XXXX __ieee80211_wake_txqs: TID 10 NOT dirty > > [ 179.585041] XXXX __ieee80211_wake_txqs: EXIT > > [ 179.585047] XXXX drv_tx: TX > > [ 179.585056] XXXX ieee80211_tx_dequeue: mark TID 0 dirty. Reason: > > 1 [ 179.585271] XXXX ieee80211_tx_dequeue: mark TID 0 dirty. > > Reason: 1 [ 179.585868] XXXX ieee80211_tx_dequeue: mark TID 0 > > dirty. Reason: 1 [ 179.586120] XXXX ieee80211_tx_dequeue: mark TID > > 0 dirty. Reason: 1 [ 179.586544] XXXX ieee80211_tx_dequeue: mark > > TID 0 dirty. Reason: 1 [ 179.586792] XXXX ieee80211_tx_dequeue: > > mark TID 0 dirty. Reason: 1 [ 179.587317] XXXX > > ieee80211_tx_dequeue: mark TID 0 dirty. Reason: 1 [ 179.587591] > > XXXX ieee80211_tx_dequeue: mark TID 0 dirty. Reason: 1 [ > > 179.588569] XXXX ieee80211_tx_dequeue: mark TID 0 dirty. Reason: 1 > > .... [ 214.307617] XXXX ieee80211_wake_queue: called > > > > > > --> So the driver blocked TX for more than 30s. Which is a good > > explanation of what Thomas observes. > > > > But there is nothing mac80211 can do differently here. Whatever is > > the real reason for the issue, it's nothing obvious I see. > > Best shot I have so far is a driver bug/issue now exposed by the > changed traffic pattern from mac80211. And while digging into the > rt2800usb driver I found a watchdog introduced here: > https://lore.kernel.org/20190615100100.29800-1-sgruszka@xxxxxxxxxx > > From mac80211 debugging it looks like it may just be that: A random > hang of the driver/card. > > For sure rt2800usb tells mac80211 to stop TXing and needs ages (>30s > in known sample) to unblock the queue. And this watchdog is disabled > by default. > > Now I'm clearly wondering, if the changed traffic pattern due to the > mac80211 patch is just triggering the random hangs... > > I've also uploaded more test patches to bugzilla. > > @Thomas > Can you also try with this watchdog enabled? It must be enabled for > rt2800lib. Since you have compiled in the driver the following boot > parameter should enable it: > rt2800lib.watchdog=1 i responded on the bugtracker. Enabling the watchdog doesn't solve the problem. > > @Stanislaw > Can you maybe also have a look at the issue and how that looks > compared to the known random hangs you introduced the watchdog for? > > > > > Luckily I found a card using the same driver and nearly the same > > card: Thomas systems:Linux version 6.2.2-gentoo (root@foo) (gcc > > (Gentoo Hardened 12.2.1_p20230121-r1 p10) 12.2.1 20230121, GNU ld > > (Gentoo 2.39 p5) 2.39.0) #2 SMP Fri Mar 3 16:59:02 CET > > 2023ieee80211 phy0: rt2x00_set_rt: Info - RT chipset 3070, rev 0201 > > detected ieee80211 phy0: rt2x00_set_rf: Info - RF chipset 0005 > > detected ieee80211 phy0: Selected rate control algorithm > > 'minstrel_ht' > > > > My system, using the kernel config from Thomas with only minor > > modifications (different filesystems and initramfs settings and > > enabled mac80211 debug and developer options): > > Linux version 6.2.2-gentoo (root@Perry.mordor) (gcc (Gentoo > > 12.2.1_p20230121-r1 p10) 12.2.1 20230121, GNU ld (Gentoo 2.40 p2) > > 2.40.0) #2 SMP Tue Mar 7 18:18:47 CET 2023ieee80211 phy0: > > rt2x00_set_rt: Info - RT chipset 3070, rev 0200 detected > > ieee80211 phy0: rt2x00_set_rf: Info - RF chipset 0005 detected > > ieee80211 phy0: Selected rate control algorithm 'minstrel_ht' > > ieee80211 phy0: rt2x00lib_request_firmware: Info - Loading firmware > > file 'rt2870.bin' > > ieee80211 phy0: rt2x00lib_request_firmware: Info - Firmware > > detected - version: 0.36 > > > > But there is one big difference on my system: I can't reproduce the > > bug so far. It's working as it should... (I did not apply the debug > > patches myself so far) > > > > I'm now planning to look a bit more into the rt2800usb driver and > > provide another debug patch for interesting looking code pieces in > > it. > > > > @Thomas: > > I've also uploaded you my binary kernel I'm running at the moment > > here: https://www.awhome.eu/s/5FjqMS73rtCtSBM > > > > That kernel should also be able to boot and operate your system. > > Can you try that and tell me, if that makes any difference? > > > > I'm also planning to provide some more debug patches, to figuring > > out which part of commit 4444bc2116ae ("wifi: mac80211: Proper mark > > iTXQs for resumption") fixes the issue for you. Assuming my > > understanding above is correct the patch should not really > > fix/break anything for you...With the findings above I would have > > expected your git bisec to identify commit a790cc3a4fad ("wifi: > > mac80211: add wake_tx_queue callback to drivers") as the first > > broken commit... > > > > Alexander >
