Re: [tip:timers/core] kselftests: timers: set-timer-lat: Tweak reporting when timer fires early

[Greg Hackmann]

On 09/20/2017 04:38 PM, Shuah Khan wrote:
> On 09/20/2017 06:31 AM, Prarit Bhargava wrote:
> > On 09/19/2017 11:36 PM, John Stultz wrote:
> > > On Tue, Sep 19, 2017 at 6:02 PM, Shuah Khan <shuah@xxxxxxxxxx> wrote:
> > > > Hi Greg,
> > > >
> > > > On 08/20/2017 03:56 AM, tip-bot for Greg Hackmann wrote:
> > > > > Commit-ID:  a524b1184b8e86141d689fa78ad150fbf2db9b4c
> > > > > Gitweb:     http://git.kernel.org/tip/a524b1184b8e86141d689fa78ad150fbf2db9b4c
> > > > > Author:     Greg Hackmann <ghackmann@xxxxxxxxxx>
> > > > > AuthorDate: Tue, 25 Jul 2017 14:36:25 -0700
> > > > > Committer:  John Stultz <john.stultz@xxxxxxxxxx>
> > > > > CommitDate: Thu, 17 Aug 2017 12:14:54 -0700
> > > > >
> > > > > kselftests: timers: set-timer-lat: Tweak reporting when timer fires early
> > > > >
> > > > > Rather than printing an error inside the alarm signal handler, set a
> > > > > flag that we check later.  This keeps the test from spamming the console
> > > > > every time the alarm fires early.  It also fixes the test exiting with
> > > > > error code 0 if this was the only test failure.
> > > > >
> > > > > Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> > > > > Cc: Ingo Molnar <mingo@xxxxxxxxxx>
> > > > > Cc: Miroslav Lichvar <mlichvar@xxxxxxxxxx>
> > > > > Cc: Richard Cochran <richardcochran@xxxxxxxxx>
> > > > > Cc: Prarit Bhargava <prarit@xxxxxxxxxx>
> > > > > Cc: Stephen Boyd <stephen.boyd@xxxxxxxxxx>
> > > > > Cc: Shuah Khan <shuah@xxxxxxxxxx>
> > > > > Cc: linux-kselftest@xxxxxxxxxxxxxxx
> > > > > Signed-off-by: Greg Hackmann <ghackmann@xxxxxxxxxx>
> > > > > Signed-off-by: John Stultz <john.stultz@xxxxxxxxxx>
> > > >
> > > > This commit is making the set-timer-lat hang. I reverted this commit
> > > > and there is no hang. Could you please take a look and see if this
> > > > commit should be reverted.
> > > >
> > > > make kselftest as well as make -C tools/testing/selftests/timers run_tests
> > > > hang.
> > >
> > > Do you have any specific details as to how the test hangs? (ie: Log
> > > data, as in where it might be when it hangs? Any details about the
> > > machine?)
> > >
> > > I'm not seeing it so far in my testing.
> >
> > I just ran it here and don't see any issues.  I'll try on a few other boxes
> > to make sure.
> >
> > # make -C tools/testing/selftests/timers run_tests
>
> John/Prarit,
>
> Thanks for getting back to me. I isolated the problem to redirecting
> test output. If I redirect the output it hangs.
>
> ./set-timer-lat > /tmp/set-timer-lat 2>&1
>
> it hangs. The reason I am seeing this is because there is a patch
> that came in recently to redirect individual test output to a separate
> file to make it easier to understand the test results.
>
> Looks like Commits 28be3f8f48cfb3cf024860f042d424cd4824f5f7 and/or
> a524b1184b8e86141d689fa78ad150fbf2db9b4c add dependency on stdin/out/err
> to the test.
>
> Anyway just an update. It can be reproduced easily. If we have tests
> that can't tolerate redirecting output, I might end up dropping the
> patch that is in linux-kselftest fixes
>
> fbcab13d2e2511a858590846ac2e2d7cbd830591
>
> So fat set-timer-lat is the only one I found.
>
> thanks,
> -- Shuah
I'm able to reproduce this locally, though I'm not sure it's a 
redirection issue.  28be3f8f48cf ("kselftests: timers: set-timer-lat: 
Add one-shot timer test cases") appears to have a regression where if 
timer_create() fails due to missing CAP_WAKE_ALARM, do_timer() will 
still try to run the test anyway.

Please revert 28be3f8f48cf and verify whether this fixes the problem for 
you.  If so, I'll send a V2 as soon as possible that fixes the issue. 
(Basically, setup_timer() needs a discrete return value for unsupported 
test cases.)

Sorry for the confusion.