use EBR to avoid life time races in callouts
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Authored by kmacy on Jun 29 2016, 6:15 AM.

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Reviewers

scottl
gallatin
• hselasky
rrs
glebius

Group Reviewers

transport

Summary

This is an alternative to further voodoo debugging, serializing the stack with the tcbinfo lock on free, or requiring API changes to callouts. The problem lies with the large technical debt in TCP's relatively poor handling of concurrency not callouts.

See D7017 for the EBR interface.

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rS FreeBSD src repository - subversion

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kmacy updated this revision to Diff 17999.Jun 29 2016, 6:15 AM

kmacy retitled this revision from to use EBR to avoid life time races in callouts.

kmacy updated this object.

kmacy edited the test plan for this revision. (Show Details)

kmacy added reviewers: scottl, rrs, • hselasky, glebius.

kmacy set the repository for this revision to rS FreeBSD src repository - subversion.

Herald added a reviewer: transport. · View Herald TranscriptJun 29 2016, 6:15 AM

Herald added a subscriber: imp. · View Herald Transcript

kmacy updated this object.Jun 29 2016, 6:16 AM

kmacy edited edge metadata.

Diff lacks context; can you generate one with -U999999?

jch added a subscriber: jch.Jun 29 2016, 7:46 AM

Add context

Herald edited edge metadata. · View Herald TranscriptJun 29 2016, 7:47 AM

Where is ebr.h?

ebr.h is in D7017 (dependency)

• hselasky added inline comments.Jun 29 2016, 12:29 PM

sys/netinet/in_pcb.c
1221	ebr_epoch_synchronize() can invoke pause() which needs a sleeping context, per D7017 which is not allowed for the context from which in_pcb_safe_free() is called ???

scottl added a reviewer: gallatin.Jun 29 2016, 3:28 PM

kmacy added a parent revision: D7017: Add basic wrapper for CK's EBR.Jun 29 2016, 7:24 PM

Always defer free in the context of an ithread.

Herald edited edge metadata. · View Herald TranscriptJun 29 2016, 7:28 PM

kbowling added a subscriber: kbowling.Jul 25 2016, 4:59 AM

kmacy abandoned this revision.Sep 21 2016, 3:55 AM

kmacy added inline comments.

sys/netinet/in_pcb.c
1221	Good point. Some last minute API changes and a late night led to at least one oversight. I'll fix and ensure that free is always deferred in an ithread.