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SubjectRe: [PATCH 0/3] rcu: synchronize_rcu[_expedited]() related fixes
On Mon, Mar 14, 2022 at 01:26:10PM -0700, Paul E. McKenney wrote:
> On Mon, Mar 14, 2022 at 02:37:35PM +0100, Frederic Weisbecker wrote:
> >
> > A few fixes especially for expedited GP polling causing a stall on TREE07,
> > as reported by Paul.
> >
> > We may still want to optimize start_poll_synchronize_rcu_expedited() on
> > UP-no-preempt but I think Paul may be implying this while doing other
> > fixes.
> >
> > git://git.kernel.org/pub/scm/linux/kernel/git/frederic/linux-dynticks.git
> > rcu/dev
> >
> > HEAD: 6e5fd7e614fd5c8f0fffeaa140b7ea697bfeb096
> >
> > Thanks,
> > Frederic
>
> I have pulled these in for review and testing, thank you!!! I have
> started a ~90-minute test and will let you know how that goes.

And TREE05 doesn't like this much. I get too-short grace periods.
TREE05 is unusual in being the one with the kernel build with
CONFIG_PREEMPT_NONE=y but also with CONFIG_PREEMPT_DYNAMIC=n.

Running tests of the commits individually.

Thanx, Paul

> > ---
> >
> > Frederic Weisbecker (2):
> > rcu: Fix expedited GP polling against UP/no-preempt environment
>
> I have some concerns with this one due to the fact that it acquires locks
> in cases where the old code would not. (I did have problems with this
> in both recent SRCU changes and the normal-grace-period counterpart to
> this series.)
>
> But let's see what rcutorture and kbuild test robot think about it.
>
> > rcu: Fix preemption mode check on synchronize_rcu[_expedited]()
>
> This one looks good.
>
> > Valentin Schneider (1):
> > preempt/dynamic: Introduce preempt mode accessors
>
> I am guessing that this one is a compact placeholder for my convenience
> (in which case thank you!). I will be marking it "EXP" on my next rebase.
>
> Thanx, Paul
>
> > include/linux/sched.h | 16 +++++++++++++++
> > kernel/rcu/tree.c | 2 +-
> > kernel/rcu/tree_exp.h | 57 +++++++++++++++++++++++++++++++--------------------
> > kernel/sched/core.c | 11 ++++++++++
> > 4 files changed, 63 insertions(+), 23 deletions(-)

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