Subject: Re: selftests: ftrace: event filter function - test event filtering on functions [FAIL]

From: Masami Hiramatsu (Google) <[email-masked]>
Date: Sun, 19 Mar 2023 00:27:58 +0900

Hi Naresh,

On Wed, 15 Mar 2023 14:41:51 +0530
Naresh Kamboju <[email-masked]> wrote:

> Hi Masami San,
> 
> 
> On Wed, 15 Mar 2023 at 14:03, Masami Hiramatsu <[email-masked]> wrote:
> >
> > Hi Naresh,
> >
> > On Tue, 14 Mar 2023 15:52:44 +0530
> > Naresh Kamboju <[email-masked]> wrote:
> >
> > > Results from Linaro’s test farm.
> > >
> > > selftests ftrace failed on qemu-x86_64 and qemu-arm64.
> > > Please find the test log below.
> >
> > Thanks for reporting!
> > Can you share the kernel config which you used for this build?
> > And the kernel is "next-20230314", is that correct?
> 
> I have attached a test log file and Kconfig file.

Thanks! I could reproduced.

The error log is here.
----
+ . /mnt/ftrace/test.d/filter/event-filter-function.tc
+ echo 'Test event filter function name'
Test event filter function name
+ echo 0
+ echo 0
+ echo
+ echo 'call_site.function == exit_mmap'
+ echo 1
+ echo 1
+ ls
+ echo 0
+ + wcgrep -l
 exit_mmap
+ grep kmem_cache_free trace
+ hitcnt=0
+ + wcgrep -l
 -v+  exit_mmap
grep kmem_cache_free trace
+ misscnt=0
+ '[' 0 -eq 0 ]
+ exit_fail
+ exit 1

And the test case is here.
-----
echo 'call_site.function == exit_mmap' > events/kmem/kmem_cache_free/filter
echo 1 > events/kmem/kmem_cache_free/enable
echo 1 > tracing_on
ls > /dev/null
echo 0 > events/kmem/kmem_cache_free/enable

hitcnt=`grep kmem_cache_free trace| grep exit_mmap | wc -l`
misscnt=`grep kmem_cache_free trace| grep -v exit_mmap | wc -l`

if [ $hitcnt -eq 0 ]; then
        exit_fail
fi
-----

The test case expects the `ls > /dev/null` involves 'kmem_cache_free' trace
event, but it doesn't.

BTW, this code is a bit fragile because the function caller can be changed
frequently. I think it should sample the events and use one of them.
Let me fix that.

Thank you,

> 
> >
> > >
> > > Is this expected to fail ? Am I missing anything ?
> >
> > No, it should be a bug. I would like to reproduce it.
> 
> - Naresh

-- 
Masami Hiramatsu (Google) <[email-masked]>