WiFi unstable (crashes around every day) TL-WR841N v9

Assuming you logged in just prior to the crash, from this entry

https://openwrt.org/toh/tp-link/tl-wr841nd -- v9: 32 MB RAM

https://openwrt.org/supported_devices/432_warning

32 MB can work for minimal router/AP functions, but may repeatedly “crash”, depending on your hardware and use case

Looking at RAM consumption after the crash isn't going to reveal that that you've run out just prior to the crash.


Edit:

One way to "watch" the memory usage would be open a terminal session (so that it's in the scrollback if the router crashes) and run something like

while printf "%s\t%s\n" "$(date)" "$(free | head -n2 | tail -n1)" ; do sleep 1 ; done

Ah, did not notice the login entry. In fact I logged in just after the crash, not before.

I thought the same, but it was suggested to do so, so I did. I guess the log might offer more relevant details.

This are the log entries just before the "crash". I think it is what caused it or at least the symptoms of it. I had a short Google search and there have been similar problems with disconnects "due to excessive missing ACKs" on other router models, but not sure whether this is the same problem here or has a different root.

Sorry, but no.
Logs do not survive crash & reboot, as logs are held in RAM in order to avoid flash writes. You will not get any useful information from new logs, which are totally about after-reboot events.

The timestamp that misleads you, is wrong. Your router has no real time clock, so it loses time after reboot. The router uses the date/time of the most recent file on /etc as an approximation of the best known last date/time before the router can update NTP time from internet. So after reboot the timestamps in the log are wrong... If you look closer at the system log, there is usually a gap/jump in time when it gets refreshed.

1 Like

You are wrong. I wrote that the router did not crash, just the WiFi went down. I was still able to login via LAN, there has not been a reboot. So the timestamps should be correct and the logs could lead to useful information.

Interesting, did not know that.

However, since the logs seem to be correct, any ideas about them? Or should I create an issue on GitHub? Also ping @nbd since I saw you were working on similar log issues with different devices:

For now I will try to use the tip from @jeff to print out RAM usage to the terminal to see whether this might be the root.

Also I should note that until now I think I only experienced this problem after using the specific device with the mac address given on the IEEE 802.11: disconnected due to excessive missing ACKs error message (fc:a6:67:c6:9f:af). It is a FireTV Stick from Amazon.

Yeah, I misunderstood the details this time as the earlier part of the thread mentions reboots. But apparently wifi just doesn't accept connection from your device, but the router itself stays alive. And actually also the authentication driver (hostapd/wpad) stays alive, as there are further log messages.

As there is nothing visible on kernel log, there has not been an actual wifi driver "crash".
(A real wifi driver crash would show up visibly in the kernel log )

It is likely some kind of lockup either in the driver or in the hostapd authentication daemon. You might try identifying the culprit by trying to restart hostapd, and/or the whole wifi via "wifi up".

But the generic reason may well be the 32 MB RAM thing. It is really problematic. It may lead to e.g. some temporary buffer allocation failing, or something like like.

1 Like

Alright, I will try that the next time it happens.

Some more details: The Web Gui still displayed all connected Clients, although they had no internet access.

Also the connections seem to have gotten back after waiting around 8 minutes automatically.

So, some more additions.

Since I did not activate the memory logging everytime, I did not have it when the crashes occurred.

Yesterday I tried a stress test meaning high streaming volumes on three connected Wifi devices and my PC to maybe provoke the crash. Unfortunately that did not work and also the free memory was rather stable and did never cause a crash.

Fortunately I enabled logging today and the Wifi just crashed now with normal use (no stress test).

The crash probably occurred around 20:40.

Memory printout (more lines at pastebin):

root@LEDE:~# while printf "%s\t%s\n" "$(date)" "$(free | head -n2 | tail -n1)" ; do sleep 1 ; done
Wed Aug 21 20:39:24 CEST 2019	Mem:         27844      19312       8532        436       1320       3940
Wed Aug 21 20:39:25 CEST 2019	Mem:         27844      19308       8536        436       1320       3940
Wed Aug 21 20:39:26 CEST 2019	Mem:         27844      19436       8408        436       1320       3940
Wed Aug 21 20:39:27 CEST 2019	Mem:         27844      19396       8448        436       1320       3940
Wed Aug 21 20:39:28 CEST 2019	Mem:         27844      19380       8464        436       1320       3940
Wed Aug 21 20:39:29 CEST 2019	Mem:         27844      19500       8344        436       1320       3940
Wed Aug 21 20:39:30 CEST 2019	Mem:         27844      19492       8352        436       1320       3940
Wed Aug 21 20:39:31 CEST 2019	Mem:         27844      19204       8640        436       1320       3940
Wed Aug 21 20:39:32 CEST 2019	Mem:         27844      19304       8540        436       1320       3940
Wed Aug 21 20:39:33 CEST 2019	Mem:         27844      19424       8420        436       1320       3940
Wed Aug 21 20:39:34 CEST 2019	Mem:         27844      19560       8284        436       1320       3940
Wed Aug 21 20:39:35 CEST 2019	Mem:         27844      19480       8364        436       1320       3940
Wed Aug 21 20:39:36 CEST 2019	Mem:         27844      19244       8600        436       1320       3940
Wed Aug 21 20:39:37 CEST 2019	Mem:         27844      19408       8436        436       1320       3940
Wed Aug 21 20:39:38 CEST 2019	Mem:         27844      19540       8304        436       1320       3940
Wed Aug 21 20:39:39 CEST 2019	Mem:         27844      19596       8248        436       1320       3940
Wed Aug 21 20:39:40 CEST 2019	Mem:         27844      19132       8712        436       1320       3940
Wed Aug 21 20:39:41 CEST 2019	Mem:         27844      19752       8092        436       1320       3940
Wed Aug 21 20:39:43 CEST 2019	Mem:         27844      19280       8564        436       1320       3940
Wed Aug 21 20:39:44 CEST 2019	Mem:         27844      19372       8472        436       1320       3940
Wed Aug 21 20:39:45 CEST 2019	Mem:         27844      19532       8312        436       1320       3940
Wed Aug 21 20:39:46 CEST 2019	Mem:         27844      19628       8216        436       1320       3940
Wed Aug 21 20:39:47 CEST 2019	Mem:         27844      19696       8148        436       1320       3940
Wed Aug 21 20:39:48 CEST 2019	Mem:         27844      19432       8412        436       1320       3940
Wed Aug 21 20:39:49 CEST 2019	Mem:         27844      19364       8480        436       1320       3940
Wed Aug 21 20:39:50 CEST 2019	Mem:         27844      19392       8452        436       1320       3940
Wed Aug 21 20:39:51 CEST 2019	Mem:         27844      19468       8376        436       1320       3940
Wed Aug 21 20:39:52 CEST 2019	Mem:         27844      19624       8220        436       1320       3940
Wed Aug 21 20:39:53 CEST 2019	Mem:         27844      19564       8280        436       1320       3940
Wed Aug 21 20:39:54 CEST 2019	Mem:         27844      19652       8192        436       1320       3940
Wed Aug 21 20:39:55 CEST 2019	Mem:         27844      19340       8504        436       1320       3940
Wed Aug 21 20:39:56 CEST 2019	Mem:         27844      19396       8448        436       1320       3940
Wed Aug 21 20:39:57 CEST 2019	Mem:         27844      19488       8356        436       1320       3940
Wed Aug 21 20:39:58 CEST 2019	Mem:         27844      19624       8220        436       1320       3940
Wed Aug 21 20:39:59 CEST 2019	Mem:         27844      19692       8152        436       1320       3940
Wed Aug 21 20:40:00 CEST 2019	Mem:         27844      19684       8160        436       1320       3940
Wed Aug 21 20:40:01 CEST 2019	Mem:         27844      19680       8164        436       1320       3940
Wed Aug 21 20:40:02 CEST 2019	Mem:         27844      19660       8184        436       1320       3940
Wed Aug 21 20:40:03 CEST 2019	Mem:         27844      19676       8168        436       1320       3940
Wed Aug 21 20:40:04 CEST 2019	Mem:         27844      19692       8152        436       1320       3940
Wed Aug 21 20:40:05 CEST 2019	Mem:         27844      19692       8152        436       1320       3940
Wed Aug 21 20:40:06 CEST 2019	Mem:         27844      19236       8608        436       1320       3940
Wed Aug 21 20:40:07 CEST 2019	Mem:         27844      19396       8448        436       1320       3940
Wed Aug 21 20:40:08 CEST 2019	Mem:         27844      19536       8308        436       1320       3940
Wed Aug 21 20:40:09 CEST 2019	Mem:         27844      19596       8248        436       1320       3940
Wed Aug 21 20:40:11 CEST 2019	Mem:         27844      19620       8224        436       1320       3940
Wed Aug 21 20:40:12 CEST 2019	Mem:         27844      19632       8212        436       1320       3940
Wed Aug 21 20:40:13 CEST 2019	Mem:         27844      19664       8180        436       1320       3940
Wed Aug 21 20:40:14 CEST 2019	Mem:         27844      19696       8148        436       1320       3940
Wed Aug 21 20:40:15 CEST 2019	Mem:         27844      19792       8052        436       1320       3940
Wed Aug 21 20:40:16 CEST 2019	Mem:         27844      19848       7996        436       1320       3940
Wed Aug 21 20:40:17 CEST 2019	Mem:         27844      19792       8052        436       1320       3940
Wed Aug 21 20:40:18 CEST 2019	Mem:         27844      19664       8180        436       1320       3940
Wed Aug 21 20:40:19 CEST 2019	Mem:         27844      19724       8120        436       1320       3940
Wed Aug 21 20:40:20 CEST 2019	Mem:         27844      19696       8148        436       1320       3940
Wed Aug 21 20:40:21 CEST 2019	Mem:         27844      19756       8088        436       1320       3940
Wed Aug 21 20:40:22 CEST 2019	Mem:         27844      19680       8164        436       1320       3940
Wed Aug 21 20:40:23 CEST 2019	Mem:         27844      19688       8156        436       1320       3940
Wed Aug 21 20:40:24 CEST 2019	Mem:         27844      19692       8152        436       1320       3940
Wed Aug 21 20:40:25 CEST 2019	Mem:         27844      19688       8156        436       1320       3940
Wed Aug 21 20:40:26 CEST 2019	Mem:         27844      19676       8168        436       1320       3940
Wed Aug 21 20:40:27 CEST 2019	Mem:         27844      19300       8544        436       1320       3940
Wed Aug 21 20:40:28 CEST 2019	Mem:         27844      19388       8456        436       1320       3940
Wed Aug 21 20:40:29 CEST 2019	Mem:         27844      19504       8340        436       1320       3940
Wed Aug 21 20:40:30 CEST 2019	Mem:         27844      19620       8224        436       1320       3940
Wed Aug 21 20:40:31 CEST 2019	Mem:         27844      19752       8092        436       1320       3940
Wed Aug 21 20:40:32 CEST 2019	Mem:         27844      19748       8096        436       1320       3940
Wed Aug 21 20:40:33 CEST 2019	Mem:         27844      19720       8124        436       1320       3940
Wed Aug 21 20:40:34 CEST 2019	Mem:         27844      19740       8104        436       1320       3940
Wed Aug 21 20:40:35 CEST 2019	Mem:         27844      19276       8568        436       1320       3940
Wed Aug 21 20:40:36 CEST 2019	Mem:         27844      19468       8376        436       1320       3940
Wed Aug 21 20:40:37 CEST 2019	Mem:         27844      19568       8276        436       1320       3940
Wed Aug 21 20:40:38 CEST 2019	Mem:         27844      19652       8192        436       1320       3940
Wed Aug 21 20:40:39 CEST 2019	Mem:         27844      19752       8092        436       1320       3940
Wed Aug 21 20:40:41 CEST 2019	Mem:         27844      19752       8092        436       1320       3940
Wed Aug 21 20:40:42 CEST 2019	Mem:         27844      19304       8540        436       1320       3940
Wed Aug 21 20:40:43 CEST 2019	Mem:         27844      19432       8412        436       1320       3940
Wed Aug 21 20:40:44 CEST 2019	Mem:         27844      19588       8256        436       1320       3940
Wed Aug 21 20:40:45 CEST 2019	Mem:         27844      19424       8420        436       1320       3940
Wed Aug 21 20:40:46 CEST 2019	Mem:         27844      19480       8364        436       1320       3940
Wed Aug 21 20:40:47 CEST 2019	Mem:         27844      19524       8320        436       1320       3940
Wed Aug 21 20:40:48 CEST 2019	Mem:         27844      19208       8636        436       1320       3940
Wed Aug 21 20:40:49 CEST 2019	Mem:         27844      19392       8452        436       1320       3940
Wed Aug 21 20:40:50 CEST 2019	Mem:         27844      19500       8344        436       1320       3940
Wed Aug 21 20:40:51 CEST 2019	Mem:         27844      19568       8276        436       1320       3940
Wed Aug 21 20:40:52 CEST 2019	Mem:         27844      19628       8216        436       1320       3940
Wed Aug 21 20:40:53 CEST 2019	Mem:         27844      19664       8180        436       1320       3940
Wed Aug 21 20:40:54 CEST 2019	Mem:         27844      19748       8096        436       1320       3940
Wed Aug 21 20:40:55 CEST 2019	Mem:         27844      19812       8032        436       1320       3940
Wed Aug 21 20:40:56 CEST 2019	Mem:         27844      19412       8432        436       1320       3940
Wed Aug 21 20:40:57 CEST 2019	Mem:         27844      19476       8368        436       1320       3940
Wed Aug 21 20:40:58 CEST 2019	Mem:         27844      19532       8312        436       1320       3940
Wed Aug 21 20:40:59 CEST 2019	Mem:         27844      19656       8188        436       1320       3940
Wed Aug 21 20:41:00 CEST 2019	Mem:         27844      19616       8228        436       1320       3940
Wed Aug 21 20:41:01 CEST 2019	Mem:         27844      19656       8188        436       1320       3940
Wed Aug 21 20:41:02 CEST 2019	Mem:         27844      19628       8216        436       1320       3940
Wed Aug 21 20:41:03 CEST 2019	Mem:         27844      19756       8088        436       1320       3940
Wed Aug 21 20:41:04 CEST 2019	Mem:         27844      19404       8440        436       1320       3940
Wed Aug 21 20:41:05 CEST 2019	Mem:         27844      19528       8316        436       1320       3940
Wed Aug 21 20:41:06 CEST 2019	Mem:         27844      19660       8184        436       1320       3940
Wed Aug 21 20:41:07 CEST 2019	Mem:         27844      19408       8436        436       1320       3940
Wed Aug 21 20:41:08 CEST 2019	Mem:         27844      19488       8356        436       1320       3940
Wed Aug 21 20:41:09 CEST 2019	Mem:         27844      19592       8252        436       1320       3940
Wed Aug 21 20:41:11 CEST 2019	Mem:         27844      19688       8156        436       1320       3940
Wed Aug 21 20:41:12 CEST 2019	Mem:         27844      19392       8452        436       1320       3940
Wed Aug 21 20:41:13 CEST 2019	Mem:         27844      19428       8416        436       1320       3940
Wed Aug 21 20:41:14 CEST 2019	Mem:         27844      19588       8256        436       1320       3940
Wed Aug 21 20:41:15 CEST 2019	Mem:         27844      19692       8152        436       1320       3940
Wed Aug 21 20:41:16 CEST 2019	Mem:         27844      19304       8540        436       1320       3940
Wed Aug 21 20:41:17 CEST 2019	Mem:         27844      19344       8500        436       1320       3940
Wed Aug 21 20:41:18 CEST 2019	Mem:         27844      19460       8384        436       1320       3940
Wed Aug 21 20:41:19 CEST 2019	Mem:         27844      19584       8260        436       1320       3940
Wed Aug 21 20:41:20 CEST 2019	Mem:         27844      19744       8100        436       1320       3940
Wed Aug 21 20:41:21 CEST 2019	Mem:         27844      19988       7856        436       1320       3940
Wed Aug 21 20:41:22 CEST 2019	Mem:         27844      19440       8404        436       1320       3940
Wed Aug 21 20:41:23 CEST 2019	Mem:         27844      19564       8280        436       1320       3940
Wed Aug 21 20:41:24 CEST 2019	Mem:         27844      19696       8148        436       1320       3940
Wed Aug 21 20:41:25 CEST 2019	Mem:         27844      19752       8092        436       1320       3940
Wed Aug 21 20:41:26 CEST 2019	Mem:         27844      19596       8248        436       1320       3940
Wed Aug 21 20:41:27 CEST 2019	Mem:         27844      19592       8252        436       1320       3940
Wed Aug 21 20:41:28 CEST 2019	Mem:         27844      19576       8268        436       1320       3940
Wed Aug 21 20:41:29 CEST 2019	Mem:         27844      19568       8276        436       1320       3940
Wed Aug 21 20:41:30 CEST 2019	Mem:         27844      19628       8216        436       1320       3940
Wed Aug 21 20:41:31 CEST 2019	Mem:         27844      20056       7788        436       1320       3940
Wed Aug 21 20:41:32 CEST 2019	Mem:         27844      19748       8096        436       1320       3940
Wed Aug 21 20:41:34 CEST 2019	Mem:         27844      19488       8356        436       1320       3940
Wed Aug 21 20:41:35 CEST 2019	Mem:         27844      19620       8224        436       1320       3940
Wed Aug 21 20:41:36 CEST 2019	Mem:         27844      19632       8212        436       1320       3940
Wed Aug 21 20:41:37 CEST 2019	Mem:         27844      19712       8132        436       1320       3940
Wed Aug 21 20:41:38 CEST 2019	Mem:         27844      19732       8112        436       1320       3940
Wed Aug 21 20:41:39 CEST 2019	Mem:         27844      19704       8140        436       1320       3940
Wed Aug 21 20:41:40 CEST 2019	Mem:         27844      19728       8116        436       1320       3940
Wed Aug 21 20:41:41 CEST 2019	Mem:         27844      19824       8020        436       1320       3940
Wed Aug 21 20:41:42 CEST 2019	Mem:         27844      19732       8112        436       1320       3940
Wed Aug 21 20:41:43 CEST 2019	Mem:         27844      19760       8084        436       1320       3940
Wed Aug 21 20:41:44 CEST 2019	Mem:         27844      19552       8292        436       1320       3940
Wed Aug 21 20:41:45 CEST 2019	Mem:         27844      19668       8176        436       1320       3940
Wed Aug 21 20:41:46 CEST 2019	Mem:         27844      19704       8140        436       1320       3940
Wed Aug 21 20:41:47 CEST 2019	Mem:         27844      19732       8112        436       1320       3940
Wed Aug 21 20:41:48 CEST 2019	Mem:         27844      19636       8208        436       1320       3940
Wed Aug 21 20:41:49 CEST 2019	Mem:         27844      19600       8244        436       1320       3940
Wed Aug 21 20:41:50 CEST 2019	Mem:         27844      19396       8448        436       1320       3940
Wed Aug 21 20:41:51 CEST 2019	Mem:         27844      19588       8256        436       1320       3940
Wed Aug 21 20:41:52 CEST 2019	Mem:         27844      19660       8184        436       1320       3940
Wed Aug 21 20:41:53 CEST 2019	Mem:         27844      19440       8404        436       1320       3940
Wed Aug 21 20:41:54 CEST 2019	Mem:         27844      19676       8168        436       1320       3940
Wed Aug 21 20:41:55 CEST 2019	Mem:         27844      19784       8060        436       1320       3940
Wed Aug 21 20:41:56 CEST 2019	Mem:         27844      19788       8056        436       1320       3940
Wed Aug 21 20:41:57 CEST 2019	Mem:         27844      19540       8304        436       1320       3940
Wed Aug 21 20:41:58 CEST 2019	Mem:         27844      19656       8188        436       1320       3940
Wed Aug 21 20:41:59 CEST 2019	Mem:         27844      19748       8096        436       1320       3940
Wed Aug 21 20:42:01 CEST 2019	Mem:         27844      20276       7568        436       1320       3940
Wed Aug 21 20:42:02 CEST 2019	Mem:         27844      19856       7988        436       1320       3940
Wed Aug 21 20:42:03 CEST 2019	Mem:         27844      19896       7948        436       1320       3940
Wed Aug 21 20:42:04 CEST 2019	Mem:         27844      19888       7956        436       1320       3940
Wed Aug 21 20:42:05 CEST 2019	Mem:         27844      19724       8120        436       1320       3940
Wed Aug 21 20:42:06 CEST 2019	Mem:         27844      19812       8032        436       1320       3940
Wed Aug 21 20:42:07 CEST 2019	Mem:         27844      19924       7920        436       1320       3940
Wed Aug 21 20:42:08 CEST 2019	Mem:         27844      19664       8180        436       1320       3940
Wed Aug 21 20:42:09 CEST 2019	Mem:         27844      19760       8084        436       1320       3940
Wed Aug 21 20:42:10 CEST 2019	Mem:         27844      19856       7988        436       1320       3940
Wed Aug 21 20:42:11 CEST 2019	Mem:         27844      19952       7892        436       1320       3940
Wed Aug 21 20:42:12 CEST 2019	Mem:         27844      19952       7892        436       1320       3940
Wed Aug 21 20:42:13 CEST 2019	Mem:         27844      19952       7892        436       1320       3940
Wed Aug 21 20:42:14 CEST 2019	Mem:         27844      20012       7832        436       1320       3940
Wed Aug 21 20:42:15 CEST 2019	Mem:         27844      19900       7944        436       1320       3940
Wed Aug 21 20:42:16 CEST 2019	Mem:         27844      20016       7828        436       1320       3940
Wed Aug 21 20:42:17 CEST 2019	Mem:         27844      19916       7928        436       1320       3940
Wed Aug 21 20:42:18 CEST 2019	Mem:         27844      19872       7972        436       1320       3940
Wed Aug 21 20:42:19 CEST 2019	Mem:         27844      20012       7832        436       1320       3940
Wed Aug 21 20:42:20 CEST 2019	Mem:         27844      19572       8272        436       1320       3940
Wed Aug 21 20:42:21 CEST 2019	Mem:         27844      19724       8120        436       1320       3940
Wed Aug 21 20:42:22 CEST 2019	Mem:         27844      19920       7924        436       1320       3940
Wed Aug 21 20:42:23 CEST 2019	Mem:         27844      20016       7828        436       1320       3940
Wed Aug 21 20:42:24 CEST 2019	Mem:         27844      19652       8192        436       1320       3940
Wed Aug 21 20:42:25 CEST 2019	Mem:         27844      19748       8096        436       1320       3940
Wed Aug 21 20:42:26 CEST 2019	Mem:         27844      19856       7988        436       1320       3940
Wed Aug 21 20:42:28 CEST 2019	Mem:         27844      19856       7988        436       1320       3940
Wed Aug 21 20:42:29 CEST 2019	Mem:         27844      19856       7988        436       1320       3940
Wed Aug 21 20:42:30 CEST 2019	Mem:         27844      19936       7908        436       1320       3940
Wed Aug 21 20:42:31 CEST 2019	Mem:         27844      19980       7864        436       1320       3940
Wed Aug 21 20:42:32 CEST 2019	Mem:         27844      19564       8280        436       1320       3940
Wed Aug 21 20:42:33 CEST 2019	Mem:         27844      19732       8112        436       1320       3940
Wed Aug 21 20:42:34 CEST 2019	Mem:         27844      19788       8056        436       1320       3940
Wed Aug 21 20:42:35 CEST 2019	Mem:         27844      19400       8444        436       1320       3940
Wed Aug 21 20:42:36 CEST 2019	Mem:         27844      19520       8324        436       1320       3940
Wed Aug 21 20:42:37 CEST 2019	Mem:         27844      19588       8256        436       1320       3940
Wed Aug 21 20:42:38 CEST 2019	Mem:         27844      19648       8196        436       1320       3940
Wed Aug 21 20:42:39 CEST 2019	Mem:         27844      19776       8068        436       1320       3940
Wed Aug 21 20:42:40 CEST 2019	Mem:         27844      19844       8000        436       1320       3940
Wed Aug 21 20:42:41 CEST 2019	Mem:         27844      19844       8000        436       1320       3940
Wed Aug 21 20:42:42 CEST 2019	Mem:         27844      19784       8060        436       1320       3940
Wed Aug 21 20:42:43 CEST 2019	Mem:         27844      19772       8072        436       1320       3940
Wed Aug 21 20:42:44 CEST 2019	Mem:         27844      19564       8280        436       1320       3940
Wed Aug 21 20:42:45 CEST 2019	Mem:         27844      19656       8188        436       1320       3940
Wed Aug 21 20:42:46 CEST 2019	Mem:         27844      19712       8132        436       1320       3940
Wed Aug 21 20:42:47 CEST 2019	Mem:         27844      19724       8120        436       1320       3940
Wed Aug 21 20:42:48 CEST 2019	Mem:         27844      19496       8348        436       1320       3940
Wed Aug 21 20:42:49 CEST 2019	Mem:         27844      19576       8268        436       1320       3940
Wed Aug 21 20:42:50 CEST 2019	Mem:         27844      19724       8120        436       1320       3940
Wed Aug 21 20:42:51 CEST 2019	Mem:         27844      19660       8184        436       1320       3940
Wed Aug 21 20:42:52 CEST 2019	Mem:         27844      19720       8124        436       1320       3940
Wed Aug 21 20:42:53 CEST 2019	Mem:         27844      19692       8152        436       1320       3940
Wed Aug 21 20:42:54 CEST 2019	Mem:         27844      19720       8124        436       1320       3940
Wed Aug 21 20:42:55 CEST 2019	Mem:         27844      19744       8100        436       1320       3940
Wed Aug 21 20:42:57 CEST 2019	Mem:         27844      19436       8408        436       1320       3940
Wed Aug 21 20:42:58 CEST 2019	Mem:         27844      19532       8312        436       1320       3940
Wed Aug 21 20:42:59 CEST 2019	Mem:         27844      19624       8220        436       1320       3940
Wed Aug 21 20:43:00 CEST 2019	Mem:         27844      19700       8144        436       1320       3940
Wed Aug 21 20:43:01 CEST 2019	Mem:         27844      19592       8252        436       1320       3940
Wed Aug 21 20:43:02 CEST 2019	Mem:         27844      19628       8216        436       1320       3940
Wed Aug 21 20:43:03 CEST 2019	Mem:         27844      19784       8060        436       1320       3940
Wed Aug 21 20:43:04 CEST 2019	Mem:         27844      19780       8064        436       1320       3940
Wed Aug 21 20:43:05 CEST 2019	Mem:         27844      19680       8164        436       1320       3940
Wed Aug 21 20:43:06 CEST 2019	Mem:         27844      19452       8392        436       1320       3940
Wed Aug 21 20:43:07 CEST 2019	Mem:         27844      19660       8184        436       1320       3940
Wed Aug 21 20:43:08 CEST 2019	Mem:         27844      19752       8092        436       1320       3940
Wed Aug 21 20:43:09 CEST 2019	Mem:         27844      19796       8048        436       1320       3940
Wed Aug 21 20:43:10 CEST 2019	Mem:         27844      19588       8256        436       1320       3940
Wed Aug 21 20:43:11 CEST 2019	Mem:         27844      19664       8180        436       1320       3940
Wed Aug 21 20:43:12 CEST 2019	Mem:         27844      19788       8056        436       1320       3940
Wed Aug 21 20:43:13 CEST 2019	Mem:         27844      19916       7928        436       1320       3940
Wed Aug 21 20:43:14 CEST 2019	Mem:         27844      19912       7932        436       1320       3940
Wed Aug 21 20:43:15 CEST 2019	Mem:         27844      19596       8248        436       1320       3940
Wed Aug 21 20:43:16 CEST 2019	Mem:         27844      19608       8236        436       1320       3940
Wed Aug 21 20:43:17 CEST 2019	Mem:         27844      19764       8080        436       1320       3940
Wed Aug 21 20:43:18 CEST 2019	Mem:         27844      19860       7984        436       1320       3940
Wed Aug 21 20:43:19 CEST 2019	Mem:         27844      19752       8092        436       1320       3940
Wed Aug 21 20:43:20 CEST 2019	Mem:         27844      19752       8092        436       1320       3940
Wed Aug 21 20:43:21 CEST 2019	Mem:         27844      19760       8084        436       1320       3940
Wed Aug 21 20:43:22 CEST 2019	Mem:         27844      19868       7976        436       1320       3940
Wed Aug 21 20:43:23 CEST 2019	Mem:         27844      19928       7916        436       1320       3940
Wed Aug 21 20:43:25 CEST 2019	Mem:         27844      20024       7820        436       1320       3940
Wed Aug 21 20:43:26 CEST 2019	Mem:         27844      19992       7852        436       1320       3940
Wed Aug 21 20:43:27 CEST 2019	Mem:         27844      19864       7980        436       1320       3940
Wed Aug 21 20:43:28 CEST 2019	Mem:         27844      19724       8120        436       1320       3940
Wed Aug 21 20:43:29 CEST 2019	Mem:         27844      19760       8084        436       1320       3940
Wed Aug 21 20:43:30 CEST 2019	Mem:         27844      19852       7992        436       1320       3940
Wed Aug 21 20:43:31 CEST 2019	Mem:         27844      19952       7892        436       1320       3940
Wed Aug 21 20:43:32 CEST 2019	Mem:         27844      20040       7804        436       1320       3940
Wed Aug 21 20:43:33 CEST 2019	Mem:         27844      19976       7868        436       1320       3940
Wed Aug 21 20:43:34 CEST 2019	Mem:         27844      19680       8164        436       1320       3940
Wed Aug 21 20:43:35 CEST 2019	Mem:         27844      19736       8108        436       1320       3940
Wed Aug 21 20:43:36 CEST 2019	Mem:         27844      19888       7956        436       1320       3940
Wed Aug 21 20:43:37 CEST 2019	Mem:         27844      20016       7828        436       1320       3940
Wed Aug 21 20:43:38 CEST 2019	Mem:         27844      19724       8120        436       1320       3940
Wed Aug 21 20:43:39 CEST 2019	Mem:         27844      19948       7896        436       1320       3940
Wed Aug 21 20:43:40 CEST 2019	Mem:         27844      20080       7764        436       1320       3940
Wed Aug 21 20:43:41 CEST 2019	Mem:         27844      20012       7832        436       1320       3940
Wed Aug 21 20:43:42 CEST 2019	Mem:         27844      20016       7828        436       1320       3940
Wed Aug 21 20:43:43 CEST 2019	Mem:         27844      20020       7824        436       1320       3940
Wed Aug 21 20:43:44 CEST 2019	Mem:         27844      20016       7828        436       1320       3940
Wed Aug 21 20:43:45 CEST 2019	Mem:         27844      20040       7804        436       1320       3940
Wed Aug 21 20:43:46 CEST 2019	Mem:         27844      20012       7832        436       1320       3940
Wed Aug 21 20:43:47 CEST 2019	Mem:         27844      20008       7836        436       1320       3940
Wed Aug 21 20:43:48 CEST 2019	Mem:         27844      19928       7916        436       1320       3940
Wed Aug 21 20:43:49 CEST 2019	Mem:         27844      19916       7928        436       1320       3940
Wed Aug 21 20:43:50 CEST 2019	Mem:         27844      20008       7836        436       1320       3940
^C

System log (does not show anything special):

Wed Aug 21 19:28:03 2019 daemon.info dnsmasq-dhcp[1490]: DHCPACK(br-lan) 192.168.1.112 fc:a6:67:c6:9f:af fire-tv-stick
Wed Aug 21 19:28:05 2019 daemon.info odhcpd[848]: Using a RA lifetime of 0 seconds on br-lan
Wed Aug 21 19:34:32 2019 daemon.info odhcpd[848]: Using a RA lifetime of 0 seconds on br-lan
Wed Aug 21 19:39:02 2019 daemon.info odhcpd[848]: Using a RA lifetime of 0 seconds on br-lan
Wed Aug 21 19:46:00 2019 daemon.info odhcpd[848]: Using a RA lifetime of 0 seconds on br-lan
Wed Aug 21 19:52:56 2019 daemon.info odhcpd[848]: Using a RA lifetime of 0 seconds on br-lan
Wed Aug 21 19:59:38 2019 daemon.info odhcpd[848]: Using a RA lifetime of 0 seconds on br-lan
Wed Aug 21 20:05:53 2019 daemon.info odhcpd[848]: Using a RA lifetime of 0 seconds on br-lan
Wed Aug 21 20:09:02 2019 daemon.info dnsmasq-dhcp[1490]: DHCPREQUEST(br-lan) 192.168.1.168 48:d6:d5:6a:85:66
Wed Aug 21 20:09:02 2019 daemon.info dnsmasq-dhcp[1490]: DHCPACK(br-lan) 192.168.1.168 48:d6:d5:6a:85:66 google-home
Wed Aug 21 20:09:17 2019 daemon.info odhcpd[848]: Using a RA lifetime of 0 seconds on br-lan
Wed Aug 21 20:13:16 2019 daemon.info odhcpd[848]: Using a RA lifetime of 0 seconds on br-lan
Wed Aug 21 20:22:45 2019 daemon.info odhcpd[848]: Using a RA lifetime of 0 seconds on br-lan
Wed Aug 21 20:26:39 2019 daemon.info odhcpd[848]: Using a RA lifetime of 0 seconds on br-lan
Wed Aug 21 20:33:14 2019 daemon.info odhcpd[848]: Using a RA lifetime of 0 seconds on br-lan
Wed Aug 21 20:33:26 2019 daemon.info dnsmasq-dhcp[1490]: DHCPREQUEST(br-lan) 192.168.1.110 68:54:fd:e6:c3:c8
Wed Aug 21 20:33:26 2019 daemon.info dnsmasq-dhcp[1490]: DHCPACK(br-lan) 192.168.1.110 68:54:fd:e6:c3:c8 echo-dot
Wed Aug 21 20:42:48 2019 daemon.info odhcpd[848]: Using a RA lifetime of 0 seconds on br-lan
Wed Aug 21 20:46:43 2019 daemon.err uhttpd[904]: luci: accepted login on / for root from fdd5:24c4:abb4::98d3:c572:7f69:31c

So as you can see the memory did not seem to drop before the crash. Thus it is probably not the reason for the crash. I will also try the suggestions of @hnyman just now.

It is. You cant log/see the moment of crash. Ive tried to remote log/USB log. Just don`t bother.
Get rid of LUCI and PPP (build yourself)
Get used to CLI

Unfortunately I did not know how to restart hostapd and did not find any helpful information via Google. So I just did wifi up (at around 21:15 where many events are logged) and that worked.

System log:

Wed Aug 21 20:46:43 2019 daemon.err uhttpd[904]: luci: accepted login on / for root from fdd5:24c4:abb4::98d3:c572:7f69:31c
Wed Aug 21 20:49:21 2019 daemon.info odhcpd[848]: Using a RA lifetime of 0 seconds on br-lan
Wed Aug 21 20:49:37 2019 daemon.notice hostapd: wlan0: AP-STA-DISCONNECTED 1c:12:b0:e0:93:0d
Wed Aug 21 20:49:37 2019 daemon.info hostapd: wlan0: STA 1c:12:b0:e0:93:0d IEEE 802.11: disassociated due to inactivity
Wed Aug 21 20:49:38 2019 daemon.notice hostapd: wlan0: AP-STA-DISCONNECTED 34:ea:34:f4:3c:42
Wed Aug 21 20:49:38 2019 daemon.info hostapd: wlan0: STA 34:ea:34:f4:3c:42 IEEE 802.11: disassociated due to inactivity
Wed Aug 21 20:49:38 2019 daemon.info hostapd: wlan0: STA 1c:12:b0:e0:93:0d IEEE 802.11: deauthenticated due to inactivity (timer DEAUTH/REMOVE)
Wed Aug 21 20:49:39 2019 daemon.info hostapd: wlan0: STA 34:ea:34:f4:3c:42 IEEE 802.11: deauthenticated due to inactivity (timer DEAUTH/REMOVE)
Wed Aug 21 20:49:51 2019 daemon.notice hostapd: wlan0: AP-STA-DISCONNECTED 3c:bd:3e:57:ee:c1
Wed Aug 21 20:49:51 2019 daemon.info hostapd: wlan0: STA 3c:bd:3e:57:ee:c1 IEEE 802.11: disassociated due to inactivity
Wed Aug 21 20:49:52 2019 daemon.info hostapd: wlan0: STA 3c:bd:3e:57:ee:c1 IEEE 802.11: deauthenticated due to inactivity (timer DEAUTH/REMOVE)
Wed Aug 21 20:49:52 2019 daemon.notice hostapd: wlan0: AP-STA-DISCONNECTED 68:54:fd:e6:c3:c8
Wed Aug 21 20:49:52 2019 daemon.info hostapd: wlan0: STA 68:54:fd:e6:c3:c8 IEEE 802.11: disassociated due to inactivity
Wed Aug 21 20:49:53 2019 daemon.info hostapd: wlan0: STA 68:54:fd:e6:c3:c8 IEEE 802.11: deauthenticated due to inactivity (timer DEAUTH/REMOVE)
Wed Aug 21 20:49:54 2019 daemon.notice hostapd: wlan0: AP-STA-DISCONNECTED 7c:49:eb:15:66:bd
Wed Aug 21 20:49:54 2019 daemon.info hostapd: wlan0: STA 7c:49:eb:15:66:bd IEEE 802.11: disassociated due to inactivity
Wed Aug 21 20:49:54 2019 daemon.notice hostapd: wlan0: AP-STA-DISCONNECTED fc:a6:67:c6:9f:af
Wed Aug 21 20:49:54 2019 daemon.info hostapd: wlan0: STA fc:a6:67:c6:9f:af IEEE 802.11: disassociated due to inactivity
Wed Aug 21 20:49:55 2019 daemon.info hostapd: wlan0: STA 7c:49:eb:15:66:bd IEEE 802.11: deauthenticated due to inactivity (timer DEAUTH/REMOVE)
Wed Aug 21 20:49:55 2019 daemon.notice hostapd: wlan0: AP-STA-DISCONNECTED 48:d6:d5:6a:85:66
Wed Aug 21 20:49:55 2019 daemon.info hostapd: wlan0: STA 48:d6:d5:6a:85:66 IEEE 802.11: disassociated due to inactivity
Wed Aug 21 20:49:55 2019 daemon.notice hostapd: wlan0: AP-STA-DISCONNECTED 40:31:3c:a4:6f:cb
Wed Aug 21 20:49:55 2019 daemon.info hostapd: wlan0: STA 40:31:3c:a4:6f:cb IEEE 802.11: disassociated due to inactivity
Wed Aug 21 20:49:55 2019 daemon.info hostapd: wlan0: STA fc:a6:67:c6:9f:af IEEE 802.11: deauthenticated due to inactivity (timer DEAUTH/REMOVE)
Wed Aug 21 20:49:56 2019 daemon.info hostapd: wlan0: STA 48:d6:d5:6a:85:66 IEEE 802.11: deauthenticated due to inactivity (timer DEAUTH/REMOVE)
Wed Aug 21 20:49:56 2019 daemon.info hostapd: wlan0: STA 40:31:3c:a4:6f:cb IEEE 802.11: deauthenticated due to inactivity (timer DEAUTH/REMOVE)
Wed Aug 21 20:49:58 2019 daemon.notice hostapd: wlan0: AP-STA-DISCONNECTED f0:d7:aa:00:7e:9d
Wed Aug 21 20:49:58 2019 daemon.info hostapd: wlan0: STA f0:d7:aa:00:7e:9d IEEE 802.11: disassociated due to inactivity
Wed Aug 21 20:49:59 2019 daemon.info hostapd: wlan0: STA f0:d7:aa:00:7e:9d IEEE 802.11: deauthenticated due to inactivity (timer DEAUTH/REMOVE)
Wed Aug 21 20:58:09 2019 daemon.info odhcpd[848]: Using a RA lifetime of 0 seconds on br-lan
Wed Aug 21 21:05:49 2019 daemon.info odhcpd[848]: Using a RA lifetime of 0 seconds on br-lan
Wed Aug 21 21:13:44 2019 daemon.info odhcpd[848]: Using a RA lifetime of 0 seconds on br-lan
Wed Aug 21 21:15:45 2019 daemon.notice hostapd: wlan0: interface state ENABLED->DISABLED
Wed Aug 21 21:15:45 2019 daemon.notice hostapd: wlan0: AP-DISABLED
Wed Aug 21 21:15:45 2019 daemon.notice hostapd: wlan0: CTRL-EVENT-TERMINATING
Wed Aug 21 21:15:45 2019 daemon.notice hostapd: nl80211: deinit ifname=wlan0 disabled_11b_rates=0
Wed Aug 21 21:15:45 2019 kern.info kernel: [250379.414460] device wlan0 left promiscuous mode
Wed Aug 21 21:15:45 2019 kern.info kernel: [250379.419447] br-lan: port 2(wlan0) entered disabled state
Wed Aug 21 21:15:45 2019 daemon.notice netifd: Network device 'wlan0' link is down
Wed Aug 21 21:15:46 2019 user.notice mac80211: Failed command: iw phy phy0 set antenna all all
Wed Aug 21 21:15:46 2019 daemon.err hostapd: Configuration file: /var/run/hostapd-phy0.conf
Wed Aug 21 21:15:46 2019 kern.info kernel: [250381.315257] IPv6: ADDRCONF(NETDEV_UP): wlan0: link is not ready
Wed Aug 21 21:15:47 2019 kern.info kernel: [250381.381199] br-lan: port 2(wlan0) entered blocking state
Wed Aug 21 21:15:47 2019 kern.info kernel: [250381.386800] br-lan: port 2(wlan0) entered disabled state
Wed Aug 21 21:15:47 2019 kern.info kernel: [250381.392979] device wlan0 entered promiscuous mode
Wed Aug 21 21:15:47 2019 daemon.notice hostapd: wlan0: interface state UNINITIALIZED->COUNTRY_UPDATE
Wed Aug 21 21:15:47 2019 daemon.err hostapd: Using interface wlan0 with hwaddr e8:94:f6:2a:c5:56 and ssid "clel"
Wed Aug 21 21:15:47 2019 daemon.notice hostapd: wlan0: interface state COUNTRY_UPDATE->ENABLED
Wed Aug 21 21:15:47 2019 daemon.notice hostapd: wlan0: AP-ENABLED
Wed Aug 21 21:15:47 2019 kern.info kernel: [250382.067816] IPv6: ADDRCONF(NETDEV_CHANGE): wlan0: link becomes ready
Wed Aug 21 21:15:47 2019 kern.info kernel: [250382.074854] br-lan: port 2(wlan0) entered blocking state
Wed Aug 21 21:15:47 2019 kern.info kernel: [250382.080514] br-lan: port 2(wlan0) entered forwarding state
Wed Aug 21 21:15:47 2019 daemon.notice netifd: Network device 'wlan0' link is up
Wed Aug 21 21:15:48 2019 daemon.info hostapd: wlan0: STA 7c:49:eb:15:66:bd IEEE 802.11: authenticated
Wed Aug 21 21:15:48 2019 daemon.info hostapd: wlan0: STA 7c:49:eb:15:66:bd IEEE 802.11: associated (aid 1)
Wed Aug 21 21:15:48 2019 daemon.notice hostapd: wlan0: AP-STA-CONNECTED 7c:49:eb:15:66:bd
Wed Aug 21 21:15:48 2019 daemon.info hostapd: wlan0: STA 7c:49:eb:15:66:bd WPA: pairwise key handshake completed (RSN)
Wed Aug 21 21:15:48 2019 daemon.info hostapd: wlan0: STA 68:54:fd:e6:c3:c8 IEEE 802.11: authenticated
Wed Aug 21 21:15:48 2019 daemon.info hostapd: wlan0: STA 68:54:fd:e6:c3:c8 IEEE 802.11: associated (aid 2)
Wed Aug 21 21:15:48 2019 daemon.notice hostapd: wlan0: AP-STA-CONNECTED 68:54:fd:e6:c3:c8
Wed Aug 21 21:15:48 2019 daemon.info hostapd: wlan0: STA 68:54:fd:e6:c3:c8 WPA: pairwise key handshake completed (RSN)
Wed Aug 21 21:15:49 2019 daemon.info dnsmasq-dhcp[1490]: DHCPREQUEST(br-lan) 192.168.1.110 68:54:fd:e6:c3:c8
Wed Aug 21 21:15:49 2019 daemon.info dnsmasq-dhcp[1490]: DHCPACK(br-lan) 192.168.1.110 68:54:fd:e6:c3:c8 echo-dot
Wed Aug 21 21:15:49 2019 daemon.info hostapd: wlan0: STA 40:31:3c:a4:6f:cb IEEE 802.11: authenticated
Wed Aug 21 21:15:49 2019 daemon.info hostapd: wlan0: STA 40:31:3c:a4:6f:cb IEEE 802.11: associated (aid 3)
Wed Aug 21 21:15:49 2019 daemon.info hostapd: wlan0: STA 34:ea:34:f4:3c:42 IEEE 802.11: authenticated
Wed Aug 21 21:15:49 2019 daemon.info hostapd: wlan0: STA 34:ea:34:f4:3c:42 IEEE 802.11: associated (aid 4)
Wed Aug 21 21:15:49 2019 daemon.info odhcpd[848]: Using a RA lifetime of 0 seconds on br-lan
Wed Aug 21 21:15:50 2019 daemon.info dnsmasq-dhcp[1490]: DHCPDISCOVER(br-lan) 7c:49:eb:15:66:bd
Wed Aug 21 21:15:50 2019 daemon.info dnsmasq-dhcp[1490]: DHCPOFFER(br-lan) 192.168.1.236 7c:49:eb:15:66:bd
Wed Aug 21 21:15:50 2019 daemon.info dnsmasq-dhcp[1490]: DHCPREQUEST(br-lan) 192.168.1.236 7c:49:eb:15:66:bd
Wed Aug 21 21:15:50 2019 daemon.info dnsmasq-dhcp[1490]: DHCPACK(br-lan) 192.168.1.236 7c:49:eb:15:66:bd yeelight-color-2
Wed Aug 21 21:15:50 2019 daemon.notice hostapd: wlan0: AP-STA-CONNECTED 34:ea:34:f4:3c:42
Wed Aug 21 21:15:50 2019 daemon.info hostapd: wlan0: STA 34:ea:34:f4:3c:42 WPA: pairwise key handshake completed (RSN)
Wed Aug 21 21:15:50 2019 daemon.info dnsmasq-dhcp[1490]: DHCPDISCOVER(br-lan) 34:ea:34:f4:3c:42
Wed Aug 21 21:15:50 2019 daemon.info dnsmasq-dhcp[1490]: DHCPOFFER(br-lan) 192.168.1.107 34:ea:34:f4:3c:42
Wed Aug 21 21:15:50 2019 daemon.info dnsmasq-dhcp[1490]: DHCPREQUEST(br-lan) 192.168.1.107 34:ea:34:f4:3c:42
Wed Aug 21 21:15:50 2019 daemon.info dnsmasq-dhcp[1490]: DHCPACK(br-lan) 192.168.1.107 34:ea:34:f4:3c:42 broadlink-rm-pro
Wed Aug 21 21:15:52 2019 daemon.info hostapd: wlan0: STA 40:31:3c:a4:6f:cb IEEE 802.11: authenticated
Wed Aug 21 21:15:52 2019 daemon.info hostapd: wlan0: STA 40:31:3c:a4:6f:cb IEEE 802.11: associated (aid 3)
Wed Aug 21 21:15:52 2019 daemon.notice hostapd: wlan0: AP-STA-CONNECTED 40:31:3c:a4:6f:cb
Wed Aug 21 21:15:52 2019 daemon.info hostapd: wlan0: STA 40:31:3c:a4:6f:cb WPA: pairwise key handshake completed (RSN)
Wed Aug 21 21:15:52 2019 daemon.info hostapd: wlan0: STA 1c:12:b0:e0:93:0d IEEE 802.11: authenticated
Wed Aug 21 21:15:52 2019 daemon.info hostapd: wlan0: STA 1c:12:b0:e0:93:0d IEEE 802.11: associated (aid 5)
Wed Aug 21 21:15:52 2019 daemon.notice hostapd: wlan0: AP-STA-CONNECTED 1c:12:b0:e0:93:0d
Wed Aug 21 21:15:52 2019 daemon.info hostapd: wlan0: STA 1c:12:b0:e0:93:0d WPA: pairwise key handshake completed (RSN)
Wed Aug 21 21:15:52 2019 daemon.info hostapd: wlan0: STA 48:d6:d5:6a:85:66 IEEE 802.11: authenticated
Wed Aug 21 21:15:52 2019 daemon.info hostapd: wlan0: STA 48:d6:d5:6a:85:66 IEEE 802.11: associated (aid 6)
Wed Aug 21 21:15:52 2019 daemon.notice hostapd: wlan0: AP-STA-CONNECTED 48:d6:d5:6a:85:66
Wed Aug 21 21:15:52 2019 daemon.info hostapd: wlan0: STA 48:d6:d5:6a:85:66 WPA: pairwise key handshake completed (RSN)
Wed Aug 21 21:15:52 2019 daemon.info dnsmasq-dhcp[1490]: DHCPREQUEST(br-lan) 192.168.1.168 48:d6:d5:6a:85:66
Wed Aug 21 21:15:52 2019 daemon.info dnsmasq-dhcp[1490]: DHCPACK(br-lan) 192.168.1.168 48:d6:d5:6a:85:66 google-home
Wed Aug 21 21:15:53 2019 daemon.info dnsmasq-dhcp[1490]: DHCPREQUEST(br-lan) 192.168.1.186 1c:12:b0:e0:93:0d
Wed Aug 21 21:15:53 2019 daemon.info dnsmasq-dhcp[1490]: DHCPACK(br-lan) 192.168.1.186 1c:12:b0:e0:93:0d fire-tablet
Wed Aug 21 21:15:53 2019 daemon.info odhcpd[848]: Using a RA lifetime of 0 seconds on br-lan

Well, I had around 8 MB of free RAM during the crash (1 second around it). So you are saying something just took 8 MB in this time? Might be true, I am not an expert. For now that does not look plausible.

I did not access LUCI during that time, also as I said I could not reproduce the crash with a stress test.

BTW: Do you have the same device? Do/did you experience the same problems? Did you create a forum post about this, so I can read more about it? Seems that you invested some time into researching your problem.

If you nearly run out of RAM the "out of memory killer" will start killing processes including important ones like hostapd and even more important ones like dropbear.

1 Like

https://openwrt.org/docs/guide-developer/quickstart-build-images

So you say it is possible that I ran out of RAM according to the log? Also, is there a way to check, whether something has been killed, like enabling more detailed logging, to see whether the "out of memory killer" did kill a process? For now there is no real proof that this happened and I want to be sure. Also, is there an easy way to reach out of RAM state with some stress test?

Sad that you did not give more details on what you experienced. Do you have the same device, is there a forum post describing the problem you had? Just posting the link to a site how to build custom images does not help.

Is it ~exactly every 24 hours?

...what's your wireless config?

I'm particularly interested in your: channel selection, power, distance optimization and group key interval; but show all of your /etc/config/wireless - blanking out sensitive things like the key, etc.

No, the crashes got less in the last few weeks.

I hope, I "blanked" all sensitive information.

root@LEDE:~# cat /etc/config/wireless 

config wifi-device 'radio0'
	option type 'mac80211'
	option channel '11'
	option hwmode '11g'
	option path 'platform/qca953x_wmac'
	option htmode 'HT20'
	option country 'DE'

config wifi-iface 'default_radio0'
	option device 'radio0'
	option network 'lan'
	option mode 'ap'
	option ssid 'ssid'
	option encryption 'psk2'
	option key 'password'

I stepped into this hw situation, however I barely noticed downtimes. I will keep an eye open and report back. Btw, <<<OpenWrt 18.06.4 r7808-ef686b7292 / LuCI openwrt-18.06 branch (git-19.170.32094-4d6d8bc)>>> on device <<<TP-Link TL-WR841N/ND v9>>>

I've got exactly same weird problem with TL-WR841N v8 running OpenWrt 15.05.1. The router is set to dumb AP mode, with minimum daemons running and maybe two clients connected over WLAN. There are two VLANS (bridge over WLAN and some switch port). In normal day, WiFi stays stable, but it stop accepting new connecting just after few hours of doing Timemachine backups. Timemachine server is running on cable connected Raspberry Pi (not on a router). I will try to stop luci too and also thinking about upgrading it's RAM. I still prefer to upgrade flash and RAM over dumping it to the trash and buy new router (mostly because I like to hack things and environmental concerns). The flash chip is on a way. After upgrade flash to 16mb I will upgrade OpenWrt to 18.06.x. But RAM upgrade is more tricky, as I don't have heat gun yet.

The question here, if there is problem with VLAN routing, because before switching to VLANS, I used default bridge mode (with much more daemons running) and at least one Timemachine backup was succesful. With VLANs, router WIFI stop acting weird after few hours, way before Timemachine backup can finish. But also remember similar router freeze before, with streaming cca 8h videos from minidlna (default bridge mode, no VLANs, but believe that time the LAN port to RasPi was dead instead and WiFi was still working).

quite unlikely that it is a RAM problem

IT still happening on 19.07.5.

I know its a bit later from the last post on this issue, but I have found that the wifi dies on the wr841n v9 (qca9533 v1) when a PS4 OG is in standby mode. This happens with even stock firmware. If you turn it completely off, the router will go for days and no wifi issue.

You could try the new ath79 images, with the replaced wifi code.