Bug 694594

Summary:	[6.2 FEAT] powerpc: re-enable dispatch trace log userspace interface
Product:	Red Hat Enterprise Linux 6	Reporter:	IBM Bug Proxy <bugproxy>
Component:	kernel	Assignee:	Steve Best <sbest>
Status:	CLOSED NOTABUG	QA Contact:	Red Hat Kernel QE team <kernel-qe>
Severity:	medium	Docs Contact:
Priority:	medium
Version:	6.2	CC:	jjarvis, nobody+PNT0273897, sbest
Target Milestone:	beta	Keywords:	FutureFeature
Target Release:	6.2
Hardware:	All
OS:	All
Whiteboard:
Fixed In Version:		Doc Type:	Enhancement
Doc Text:		Story Points:	---
Clone Of:		Environment:
Last Closed:	2011-04-29 18:47:19 UTC	Type:	---
Regression:	---	Mount Type:	---
Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:

Description IBM Bug Proxy 2011-04-07 17:52:46 UTC

1. Feature Overview:
Feature Id: [71058]
a. Name of Feature: [6.2 FEAT] powerpc: re-enable dispatch trace log userspace interface
b. Feature Description
Since the cpu accounting code uses the hypervisor dispatch trace log now when
CONFIG_VIRT_CPU_ACCOUNTING = y, disabled access to it via files in the
/sys/kernel/debug/powerpc/dtl/ directory in that case. This restores those files. To do this, we
now have a hook that the cpu accounting code will call as it processes each entry from the
hypervisor dispatch trace log. The code in dtl.c now uses that to fill up its ring buffer, rather
than having the hypervisor fill the ring buffer directly. This also fixes dtl_file_read() to handle
overflow conditions a bit better and adds a spinlock to ensure that race conditions (multiple
processes opening or reading the file concurrently) are handled correctly.

2. Feature Details:
Sponsor: Power Kernel
Architectures: ppc64,
Arch Specificity: purely arch specific code
Affects Kernel Modules: No
Delivery Mechanism: Backport
Category: kernel
Request Type: Kernel - Enhancement from IBM
d. Upstream Acceptance: Accepted
Sponsor Priority P3
f. Severity: normal
IBM Confidential: No
Code Contribution: IBM code
g. Component Version Target: ---

3. Business Case
Any userspace tools that depend on the /sys/kernel/debug/powerpc/dtl interface will not function
when CONFIG_VIRT_CPU_ACCOUNTING = y. This enables those tools to function again. This also resolves
some bugs with the sysfs interface.

4. Primary contact at Red Hat:
John Jarvis, jjarvis

5. Primary contacts at Partner:
Project Management Contact:
Michael L. Hohnbaum, hbaum.com

Technical contact(s):
NISHANTH ARAVAMUDAN, aravam.com

Comment 2 RHEL Program Management 2011-04-07 18:03:59 UTC

Since RHEL 6.1 External Beta has begun, and this bug remains
unresolved, it has been rejected as it is not proposed as
exception or blocker.

Red Hat invites you to ask your support representative to
propose this request, if appropriate and relevant, in the
next release of Red Hat Enterprise Linux.

Comment 3 IBM Bug Proxy 2011-04-28 20:41:03 UTC

------- Comment From nacc.com 2011-04-28 16:32 EDT-------
Upstream commit is 872e439a45ed4a4bd499bc55cb0dffa74027f749

Comment 4 IBM Bug Proxy 2011-04-29 18:20:39 UTC

------- Comment From hohnbaum.com 2011-04-29 14:16 EDT-------
IBM is quitting this feature request as it has been resolved as part of a 6.1 feature:

> Upstream commit is 872e439a45ed4a4bd499bc55cb0dffa74027f749

> Argh, it seems this has already been resolved with the patch from BZ 66961 (RH 633515)