[stable-rc 5.9] BUG: Invalid wait context on arm64 db410c device

[Naresh Kamboju]

While booting stable rc 5.9.9-rc1 kernel on arm64 Qualcomm db410c device
the following BUG: Invalid wait context noticed.

This issue has not reproduced after several testing loops.

[   18.667840]
[   18.667865] =============================
[   18.668392] [ BUG: Invalid wait context ]
[   18.672301] 5.9.9-rc1 #1 Not tainted
[   18.676291] -----------------------------
[   18.679939] systemd-udevd/415 is trying to lock:
[   18.683846] ffff00003a73c718 (&mm->mmap_lock){++++}-{3:3}, at:
__might_fault+0x60/0xa8
[   18.688537] other info that might help us debug this:
[   18.696259] context-{4:4}
[   18.701379] 1 lock held by systemd-udevd/415:
[   18.703982]  #0: ffff800012781a38 (rcu_read_lock){....}-{1:2}, at:
xa_load+0x0/0x178
[   18.708328] stack backtrace:
[   18.716137] CPU: 0 PID: 415 Comm: systemd-udevd Not tainted 5.9.9-rc1 #1
[   18.719003] Hardware name: Qualcomm Technologies, Inc. APQ 8016 SBC (DT)
[   18.725687] Call trace:
[   18.732369]  dump_backtrace+0x0/0x1f8
[   18.734540]  show_stack+0x2c/0x38
[   18.738360]  dump_stack+0xec/0x158
[   18.741658]  __lock_acquire+0x520/0x1478
[   18.744956]  lock_acquire+0x120/0x4c8
[   18.749035]  __might_fault+0x84/0xa8
[   18.752597]  copy_page_to_iter+0xb4/0x3e8
[   18.756242]  generic_file_buffered_read+0x4bc/0xa98
[   18.760148]  generic_file_read_iter+0xd4/0x168
[   18.764836]  blkdev_read_iter+0x50/0x78
[   18.769349]  new_sync_read+0x100/0x1a0
[   18.773082]  vfs_read+0x1b4/0x1d8
[   18.776900]  ksys_read+0x74/0xf8
[   18.780286]  __arm64_sys_read+0x24/0x30
[   18.783586]  el0_svc_common.constprop.3+0x7c/0x198
[   18.787143]  do_el0_svc+0x34/0xa0
[   18.792005]  el0_sync_handler+0x16c/0x210
[   18.795390]  el0_sync+0x140/0x180

Reported-by: Naresh Kamboju <naresh.kamboju@xxxxxxxxxx>

full test log details,
https://qa-reports.linaro.org/lkft/linux-stable-rc-linux-5.9.y/build/v5.9.8-256-gfb1622495321/testrun/3452274/suite/linux-log-parser/test/check-kernel-bug-1951524/log
https://lkft.validation.linaro.org/scheduler/job/1951524#L4210

metadata:
  git branch: linux-5.9.y
  git repo: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable-rc.git
  git commit: fb1622495321923cbb1ae2c6cf2da1e9ca286800
  git describe: v5.9.8-256-gfb1622495321
  make_kernelversion: 5.9.9-rc1
  kernel-config:
http://snapshots.linaro.org/openembedded/lkft/lkft/sumo/dragonboard-410c/lkft/linux-stable-rc-5.9/32/config

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