Add function to OSD to get values without taking the lock.
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Authored by stevek on Thu, Apr 4, 12:18 AM.

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Summary

There are some cases of OSD use where the value is only initialized once
at a point where successive access of the value can be done so safely
without the need to take the lock.

Obtained from: Juniper Networks, Inc.

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rG FreeBSD src repository

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Buildable 57325
Build 54213: arc lint + arc unit

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stevek created this revision.Thu, Apr 4, 12:18 AM

Herald added subscribers: olce, imp. · View Herald TranscriptThu, Apr 4, 12:18 AM

stevek requested review of this revision.Thu, Apr 4, 12:18 AM

Harbormaster completed remote builds in B56910: Diff 136513.Thu, Apr 4, 12:18 AM

Some uses of OSD may do so in a way where the value is only set once at a point where successive get of the value can be done so safely without the need to take the lock.

I think this sentence is not quite right. :)

sys/kern/kern_osd.c
281	`osd_get_unlocked()` would be more consistent with this kind of pattern elsewhere in the tree.
291

Changed from _nolock to _unlocked in naming and updated commit log message.

Harbormaster completed remote builds in B57325: Diff 137605.Wed, Apr 24, 6:14 PM

stevek edited the summary of this revision. (Show Details)Wed, Apr 24, 6:15 PM

markj added inline comments.Thu, Apr 25, 1:19 PM

sys/kern/kern_osd.c
291	Assuming you just didn't see it, I think this suggestion should still be applied. Or is there some reason not to?

stevek added inline comments.Tue, Apr 30, 8:51 PM

sys/kern/kern_osd.c
291	I probably would not be necessary in the cases that I have seen where unlocked access makes sense. However, I suppose one could do this for some of the potential cases, but wouldn't atomic_store_ptr be necessary also in the osd_set_reserved() function if doing so?