rangelock: add rangelock_cookie_assert
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Authored by kevans on Sep 12 2019, 11:05 PM.

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rS352350: rangelock: add rangelock_cookie_assert

Summary

An approach to D21391 using rangelocks instead of an sx for the shm seal lock would have shm_dotruncate_locked take a cookie and assert that it's been granted a write lock to leave the locking out of the _locked function.

I do not yet know how I like the rangelock approach, but I think this is a good idea if we go that route.

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rS FreeBSD src repository - subversion

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Buildable 26449

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kevans created this revision.Sep 12 2019, 11:05 PM

Herald added a subscriber: imp. · View Herald TranscriptSep 12 2019, 11:05 PM

Harbormaster completed remote builds in B26449: Diff 62012.Sep 12 2019, 11:05 PM

kib added inline comments.Sep 13 2019, 5:37 AM

sys/kern/kern_rangelock.c
316	I would suggest to use KASSERT() instead of direct panic(9) call.
329	Why rl_q_flags instead of flags ? Also I do not think that RCA_UNLOCKED assert could be made safe.
sys/sys/rangelock.h
101	I suspect it is too far in cargo cult. It is fine to define RCA_XXX as plain constants, I do not see a need in any services from sys/lock.h.

kevans added inline comments.Sep 13 2019, 3:34 PM

sys/kern/kern_rangelock.c
316	Hmm... this makes rangelock_cookie_assert useless if kernel is compiled with INVARIANT_SUPPORT but not INVARIANTS and one still wants to do rangelock cookie assertions in a module. Is this intended/desired?
329	Ah, missed converting that one. True- I'll drop RCA_UNLOCKED.

kib added inline comments.Sep 13 2019, 6:06 PM

sys/kern/kern_rangelock.c
316	I am not sure that we need support for rangelocking asserts without INVARIANTs, but I understand your point. In any case I do not insist on this.

Drop RCA_UNLOCKED and cookie cutter sys/lock.h dependency. Leaving the direct panic() as _rangelock_cookie_assert cannot be called on !INVARIANTS files anyways.

Harbormaster completed remote builds in B26488: Diff 62069.Sep 13 2019, 9:44 PM

kevans marked 4 inline comments as done.Sep 13 2019, 9:45 PM

kib accepted this revision.Sep 14 2019, 8:57 AM

This revision is now accepted and ready to land.Sep 14 2019, 8:57 AM

Closed by commit rS352350: rangelock: add rangelock_cookie_assert (authored by kevans). · Explain WhySep 15 2019, 3:00 AM

This revision was automatically updated to reflect the committed changes.

kevans added a commit: rS352350: rangelock: add rangelock_cookie_assert.