1 without the interlock
ClosedPublic
Actions

Authored by mjg on Jan 15 2020, 3:03 AM.

Details

Reviewers

kib
jeff

Commits

rS356884: vfs: allow v_holdcnt to transition 0->1 without the interlock

Summary

Similarly to use count, we only care about vget and vref for which the contract has not changed. Since r356672 vnode activation only requires freevnodes update which we can accomodate without the interlock.

Diff Detail

Repository

rS FreeBSD src repository - subversion

Lint

Lint Not Applicable

Unit

Tests Not Applicable

Event Timeline

mjg created this revision.Jan 15 2020, 3:03 AM

Herald added a subscriber: imp. · View Herald TranscriptJan 15 2020, 3:03 AM

Harbormaster completed remote builds in B28676: Diff 66765.Jan 15 2020, 3:03 AM

jeff added inline comments.Jan 17 2020, 11:58 PM

sys/kern/vfs_subr.c
3354 ↗	(On Diff #66765)	This requires a little longer comment. I think I understand it but it would be nice to have a little more language around it.

mjg added inline comments.Jan 18 2020, 12:08 AM

sys/kern/vfs_subr.c
3354 ↗	(On Diff #66765)	How about this: By the time we get here another thread might have called vhold and we have no way of knowing if it was followed by vlazy. Unlinking from the list would be a bug if it was and letting it stay is harmless in either case. Thus don't do anything if someone is using the vnode.

jeff added inline comments.Jan 18 2020, 12:19 AM

sys/kern/vfs_subr.c
3354 ↗	(On Diff #66765)	"Don't remove the vnode from the lazy list if another thread has increased the hold count. It may have re-enqueued the vnode to the lazy list and is now responsible for its removal"