[Bug 283903] rtw88: possible skb leak

https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=283903

--- Comment #9 from Guillaume Outters <guillaume-freebsd@outters.eu> ---
OK, I was wrong thinking the compiler eating mem induced rtw88 into error:
now I'm convinced that rtw88 ate so much mem that clang hadn't enough anymore.

Twice this week I observed lpkiskb going rogue, unfortunately without detecting
the precise moment it became Mr Hyde.

But (as seen in https://bz-attachments.freebsd.org/attachment.cgi?id=256704),
I managed to test a loop of a 2 MB scp every minute, while watching vmstat -m |
grep lkpiskb,
with surprising results:

A. Before going rogue

Each scp added to the req counter, but memory stayed remarkably stable, at 16
MB.
I didn't even noticed any temporary increase of mem use during scps (and
statistically, my probe every 10 seconds should have happened multiple times
simultaneously with my 4 seconds lasting download).

B. After having gone rogue

Now the reqs are still there (hopefully!), but **mem use increases of ~ 3,4
MB** per scp of 2 MB (/!\ those are file bytes, not bandwidth; and I don't know
the bandwidth / file bytes ratio of scp)

And having the server lag helped saw something more interesting, due to
multiple probes occurring during the transfer:
the 3,4 MB didn't follow a monotonic growth, but instead the mem use increased
considerably, and _only some_ mem got freed once scp finished.  

--------------------------------------------------------------------------------

Here a one-go increase (probes at :45 and :56, scp occured around between :47
and :51) (+ 3,4 MB):
2025-01-14 01:06:45             lkpiskb 329256  1361215488      9513310        
+2      +8192   +212
2025-01-14 01:06:56             lkpiskb 330093  1364643840      9517636        
+837    +3428352        +4326
2025-01-14 01:07:06             lkpiskb 330095  1364652032      9517845        
+2      +8192   +209

Here a two-go (+ 5 MB - 1,6 MB):
2025-01-14 01:07:47             lkpiskb 330115  1364733952      9518743        
+5      +20480  +223
2025-01-14 01:07:57             lkpiskb 331360  1369833472      9522027        
+1245   +5099520        +3284
2025-01-14 01:08:07             lkpiskb 330958  1368186880      9523298        
-402    -1646592        +1271
2025-01-14 01:08:17             lkpiskb 330964  1368211456      9523527        
+6      +24576  +229

Another one-go (+ 6,8 MB - 3,4 MB):
2025-01-14 01:10:00             lkpiskb 331828  1371750400      9529814        
+2      +8192   +217
2025-01-14 01:10:10             lkpiskb 333506  1378623488      9534152        
+1678   +6873088        +4338
2025-01-14 01:10:20             lkpiskb 332671  1375203328      9534368        
-835    -3420160        +216
2025-01-14 01:10:30             lkpiskb 332674  1375215616      9534584        
+3      +12288  +216

Here periodic security on the server made it really hard for scp to finish, and
let rtw88 free its mem:
2025-01-14 07:21:34             lkpiskb 586598  2415288320      11209247       
        +291    +1191936        +933
2025-01-14 07:21:57             lkpiskb 587114  2417401856      11210910       
        +516    +2113536        +1663
2025-01-14 07:22:23             lkpiskb 587579  2419306496      11212416       
        +465    +1904640        +1506
2025-01-14 07:22:45             lkpiskb 587877  2420527104      11213510       
        +298    +1220608        +1094
2025-01-14 07:23:07             lkpiskb 588170  2421727232      11214571       
        +293    +1200128        +1061
2025-01-14 07:23:29             lkpiskb 588474  2422972416      11215673       
        +304    +1245184        +1102
2025-01-14 07:23:49             lkpiskb 587441  2418741248      11216292       
        -1033   -4231168        +619

--------------------------------------------------------------------------------

while true ; do date "+%Y-%m-%d %H:%M:%S" ; vmstat -m | grep lkpi ; sleep 10 ;
done | tee -a ~/tmp/depuisboot.log
awk < ~/tmp/depuisboot.log
'/^2025-/{h=$0}/lkpiskb/{variation="+"(-use+$2)"\t+"(-mem+$3)"\t+"(-req+$4);gsub(/[+]-/,"-",variation);gsub(/
+/,"\t");print h"\t"$0"\t"variation;use=0+$2;mem=0+$3;req=0+$4}' | less

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