32-bit powerpc head -r360311: lock order reversal between: "PROC (UMA zone)" and "kernelpmap (kernelpmap)": Is this expected?

From: Mark Millard <marklmi_at_yahoo.com>
Date: Thu, 30 Apr 2020 18:30:33 -0700
Using artifact.ci's head -r360311 debug-kernel materials:

https://artifact.ci.freebsd.org/snapshot/head/r360311/powerpc/powerpc/kernel*.txz

I got the following notice:

lock order reversal:
 1st 0x1cbb680 PROC (UMA zone) _at_ /usr/src/sys/vm/uma_core.c:4387
 2nd 0x113c99c kernelpmap (kernelpmap) _at_ /usr/src/sys/powerpc/aim/mmu_oea.c:1524
stack backtrace:
#0 0x5d1e5c at witness_debugger+0x94
#1 0x5d1b34 at witness_checkorder+0xb50
#2 0x51d774 at __mtx_lock_flags+0xcc
#3 0x90902c at moea_kextract+0x5c
#4 0x9462ac at pmap_kextract+0x98
#5 0x8a417c at zone_release+0xf0
#6 0x8abc14 at bucket_drain+0x2f0
#7 0x8ab64c at bucket_free+0x54
#8 0x8ab8bc at bucket_cache_reclaim+0x1bc
#9 0x8ab3c4 at zone_reclaim+0x128
#10 0x8a7e60 at uma_reclaim+0x1d0
#11 0x8d96ac at vm_pageout_worker+0x4d8
#12 0x8d91c0 at vm_pageout+0x1b0
#13 0x4f67a0 at fork_exit+0xb0
#14 0x94892c at fork_trampoline+0xc

Is the above interesting or is it one of the
known-safe lock order reversals that should
be ignored?

(The notice is from something like 4.5 hours
before I noticed it.)

===
Mark Millard
marklmi at yahoo.com
( dsl-only.net went
away in early 2018-Mar)
Received on Thu Apr 30 2020 - 23:30:42 UTC

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