Bug 1429640 – [rt] ipc/msg: Implement lockless pipelined wakeups

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Bug 1429640 - [rt] ipc/msg: Implement lockless pipelined wakeups

Summary:	[rt] ipc/msg: Implement lockless pipelined wakeups

Status:	CLOSED ERRATA

Aliases:	None

Product:	Red Hat Enterprise Linux 7
Classification:	Red Hat
Component:	kernel-rt (Show other bugs)
Sub Component:
Version:	7.4
Hardware:	x86_64 Linux

Priority	medium Severity medium
Target Milestone:	rc
Target Release:	---
Assigned To:	Clark Williams
QA Contact:	Jiri Kastner
Docs Contact:

URL:
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Depends On:
Blocks:	1353018 1410158
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Reported:	2017-03-06 13:10 EST by Clark Williams
Modified:	2017-08-01 20:25 EDT (History)
CC List:	4 users (show)

See Also:
Fixed In Version:
Doc Type:	If docs needed, set a value
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Story Points:	---
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Environment:
Last Closed:	2017-08-01 15:02:59 EDT
Type:	Bug
Regression:	---
Mount Type:	---
Documentation:	---
CRM:
Verified Versions:
Category:	---
oVirt Team:	---
RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---

Attachments	(Terms of Use)
ipc/msg: Implement lockless pipelined wakeups (6.00 KB, patch) 2017-03-06 13:12 EST, Clark Williams	no flags	Details \| Diff
ipc/msg: Implement lockless pipelined wakeups (v4) (7.19 KB, patch) 2017-04-11 16:53 EDT, Luis Claudio R. Goncalves	no flags	Details \| Diff
Show Obsolete (1) Add an attachment (proposed patch, testcase, etc.)

External Trackers
Tracker	ID	Priority	Status	Summary	Last Updated
Red Hat Product Errata	RHSA-2017:2077	normal	SHIPPED_LIVE	Important: kernel-rt security, bug fix, and enhancement update	2017-08-01 14:13:37 EDT

Groups: None (edit)

Description Clark Williams 2017-03-06 13:10:19 EST

Move the wakeup_process() invocation so it is not done under
the perm->lock by making use of a lockless wake_q. With this change, the
waiter is woken up once the message has been assigned and it does not
need to loop on SMP if the message points to NULL. In the signal case we
still need to check the pointer under the lock to verify the state.

This change should also avoid the introduction of preempt_disable() in
-RT which avoids a busy-loop which pools for the NULL -> !NULL
change if the waiter has a higher priority compared to the waker.

Comment 2 Clark Williams 2017-03-06 13:12 EST

Created attachment 1260532 [details]
ipc/msg: Implement lockless pipelined wakeups

Ported to -586 build of RHEL-RT

Comment 3 Clark Williams 2017-03-07 09:46:33 EST

tested with scratch build: 

https://brewweb.engineering.redhat.com/brew/taskinfo?taskID=12694532

Comment 6 Luis Claudio R. Goncalves 2017-04-11 16:53 EDT

Created attachment 1270949 [details]
ipc/msg: Implement lockless pipelined wakeups (v4)

Comment 10 errata-xmlrpc 2017-08-01 15:02:59 EDT

Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://access.redhat.com/errata/RHSA-2017:2077

Comment 11 errata-xmlrpc 2017-08-01 20:25:36 EDT

Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://access.redhat.com/errata/RHSA-2017:2077

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