Bug 695283

Summary:	function_graph is not listed in /sys/kernel/debug/tracing/available_tracers, but /boot/config shows it as enabled
Product:	[Fedora] Fedora	Reporter:	Robin Green <greenrd>
Component:	kernel	Assignee:	Kernel Maintainer List <kernel-maint>
Status:	CLOSED NOTABUG	QA Contact:	Fedora Extras Quality Assurance <extras-qa>
Severity:	low	Docs Contact:
Priority:	unspecified
Version:	14	CC:	gansalmon, itamar, jonathan, kernel-maint, madhu.chinakonda, srostedt
Target Milestone:	---
Target Release:	---
Hardware:	i686
OS:	Linux
Whiteboard:
Fixed In Version:		Doc Type:	Bug Fix
Doc Text:		Story Points:	---
Clone Of:		Environment:
Last Closed:	2011-04-12 15:54:00 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 Robin Green 2011-04-11 10:22:00 UTC

Description of problem:
According to /boot/config-2.6.35.11-83.fc14.i686.PAE, function_graph tracing is configured:

CONFIG_HAVE_FUNCTION_GRAPH_TRACER=y

but it doesn't show up in /sys/kernel/debug/tracing/available_tracers

Version-Release number of selected component (if applicable):
kernel-PAE-2.6.35.11-83.fc14.i686

How reproducible:
Haven't tried

Steps to Reproduce:
1. Mount debugfs at /sys/kernel/debug
2. cat /sys/kernel/debug/tracing/available_tracers
  
Actual results:
ksym_tracer blk kmemtrace wakeup_rt wakeup function sysprof sched_switch nop

Expected results:
A list that includes function_graph

Additional info:
This problem was reported last year by someone else on LKML with a self-built kernel, but there were no replies on-list.

Comment 1 Robin Green 2011-04-12 15:54:00 UTC

It's not supported on x86 unless CC_OPTIMIZE_FOR_SIZE is disabled, which is enabled in the Fedora kernel.