Michal Hocko wrote:

quoted

Strictly speaking, neither debug_show_all_locks() nor debug_show_held_locks()
are safe enough to guarantee that the system won't crash.

  commit 856848737bd944c1 "lockdep: fix debug_show_all_locks()"
  commit 82a1fcb90287052a "softlockup: automatically detect hung TASK_UNINTERRUPTIBLE tasks"

They are convenient but we should avoid using them if we care about
possibility of crash.

I really fail to see your point. debug_show_all_locks doesn't mention
any restriction of the risk nor it is restricted to a particular
context. Were there some bugs in that area? Probably yes, so what?

commit 856848737bd944c1 changed that locks held by TASK_RUNNING tasks
are not reported. We might fail to report the task which is holding mmap_sem
for write when we call debug_show_all_locks() in order to find such task.
Therefore, I think guessing from sched_show_task() output can be used.

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