Re: [PATCH 0/5] srcu fixes

Frederic Weisbecker
2023-10-04T09:36:55Z

On Tue, Oct 03, 2023 at 08:30:45PM -0700, Paul E. McKenney wrote:
> On Tue, Oct 03, 2023 at 08:21:42PM -0700, Paul E. McKenney wrote:
> > On Tue, Oct 03, 2023 at 05:35:31PM -0700, Paul E. McKenney wrote:
> > > On Wed, Oct 04, 2023 at 01:28:58AM +0200, Frederic Weisbecker wrote:
> > > > Hi,
> > > >
> > > > This contains a fix for "SRCU: kworker hung in synchronize_srcu":
> > > >
> > > > http://lore.kernel.org/CANZk6aR+CqZaqmMWrC2eRRPY12qAZnDZLwLnHZbNi=xXMB401g@mail.gmail.com
> > > >
> > > > And a few cleanups.
> > > >
> > > > Passed 50 hours of SRCU-P and SRCU-N.
> > > >
> > > > git://git.kernel.org/pub/scm/linux/kernel/git/frederic/linux-dynticks.git
> > > > srcu/fixes
> > > >
> > > > HEAD: 7ea5adc5673b42ef06e811dca75e43d558cc87e0
> > > >
> > > > Thanks,
> > > > Frederic
> > >
> > > Very good, and a big "Thank You!!!" to all of you!
> > >
> > > I queued this series for testing purposes, and have started a bunch of
> > > SRCU-P and SRCU-N tests on one set of systems, and a single SRCU-P and
> > > SRCU-N on another system, but with both scenarios resized to 40 CPU each.
>
> The 200*1h of SRCU-N and the 100*1h of SRCU-p passed other than the usual
> tick-stop errors. (Is there a patch for that one?) The 40-CPU SRCU-N
> run was fine, but the 40-CPU SRCU-P run failed due to the fanouts setting
> a maximum of 16 CPUs. So I started a 10-hour 40-CPU SRCU-P and a pair
> of 10-hour 16-CPU SRCU-N runs on one system, and 200*10h of SRCU-N and
> 100*10h of SRCU-P.
>
> I will let you know how it goes.

Very nice! It might be worth testing the first patch alone as
well if we backport only this one.

Thanks!

> Thanx, Paul
>
> > > While that is in flight, a few questions:
> > >
> > > o Please check the Co-developed-by rules. Last I knew, it was
> > > necessary to have a Signed-off-by after each Co-developed-by.
> > >
> > > o Is it possible to get a Tested-by from the original reporter?
> > > Or is this not reproducible?
> > >
> > > o Is it possible to convince rcutorture to find this sort of
> > > bug? Seems like it should be, but easy to say...
> >
> > And one other thing...
> >
> > o What other bugs like this one are hiding elsewhere
> > in RCU?
> >
> > > o Frederic, would you like to include this in your upcoming
> > > pull request? Or does it need more time?
> >
> > Thanx, Paul
> >
> > > > ---
> > > >
> > > > Frederic Weisbecker (5):
> > > > srcu: Fix callbacks acceleration mishandling
> > > > srcu: Only accelerate on enqueue time
> > > > srcu: Remove superfluous callbacks advancing from srcu_start_gp()
> > > > srcu: No need to advance/accelerate if no callback enqueued
> > > > srcu: Explain why callbacks invocations can't run concurrently
> > > >
> > > >
> > > > kernel/rcu/srcutree.c | 55 ++++++++++++++++++++++++++++++++++++---------------
> > > > 1 file changed, 39 insertions(+), 16 deletions(-)