I met same panic too, and enabled lockdep in kernel 4.19.67, the log is:
[17672.449102] RIP: 0033:0x7ff5680c4437
[17672.449643] Code: 00 00 90 48 8b 05 59 aa 0c 00 64 c7 00 26 00 00 00 48 c7
c0 ff ff ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 b8 10 00 00 00 0f 05 <48> 3d 01
f0 ff ff 73 01 c3 48 8b 0d 29 aa 0c 00 f7 d8 64 89 01 48
[17672.452380] RSP: 002b:00007ffcf6fa8a38 EFLAGS: 00003246 ORIG_RAX:
0000000000000010
[17672.453502] RAX: 0000000000000000 RBX: 00007ffcf6fa8da0 RCX: 00007ff5680c4437
[17672.454558] RDX: 00007ffcf6fa8ab0 RSI: 0000000040106442 RDI: 000000000000000e
[17672.455613] RBP: 00007ffcf6fa8ab0 R08: 000000000000000e R09: 0000000100311000
[17672.456667] R10: 0000000000000001 R11: 0000000000003246 R12: 0000000040106442
[17672.457731] R13: 000000000000000e R14: 0000000000000000 R15: 0000000000000000
[17672.459051] ================================================
[17672.459901] WARNING: lock held when returning to user space!
[17672.460762] 4.19.67 #6 Tainted: G E
[17672.461630] ------------------------------------------------
[17672.462475] Xorg/2857 is leaving the kernel with locks still held!
[17672.463394] 2 locks held by Xorg/2857:
[17672.463960] #0: 0000000092bc956a (reservation_ww_class_acquire){+.+.}, at:
qxl_release_reserve_list+0x63/0x150 [qxl]
[17672.465532] #1: 0000000014261f9b (reservation_ww_class_mutex){+.+.}, at:
ttm_eu_reserve_buffers+0x3c1/0x5c0 [ttm]
So it should be not release ww lock when exit, after parse, it's corresponding
to ww_mutex_lock_slow_interruptible in ttm_eu_reserve_buffers. I review
ttm_eu_reserve_buffers and qxl_release_reserve_list in the matser kernel 5.10,
the function logic is still same, so I beleive this issue should still exist in
kernel tip code.
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https://bugs.launchpad.net/bugs/1813620
Title:
Xorg indefinitely hangs in kernelspace at least 2-3 times a day
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