On Thu, Sep 16, 2021 at 02:10:44PM +0200, Frederic Weisbecker wrote: > This eventually removes rcu_data.exp_deferred_qs to use > rcu_data.cpu no_qs.b.exp instead. > > For those like me who need a headlamp to walk there: https://ibb.co/3d06r0V > > git://git.kernel.org/pub/scm/linux/kernel/git/frederic/linux-dynticks.git > rcu/dev > > HEAD: 7d9d8a0c6141f95cbac4367b12e755bfabb383ee Applied and pushed with some additional marking and commit-log editing. The marking is needed because rcu_qs() can be invoked with interrupts enabled, which can result in a low-probability data race with the expedited IPI handler rcu_exp_handler(). There was another access in sync_sched_exp_online_cleanup() than needed marking, so I am queuing a separate commit for that one. I suspect that this problem predated your series. This is a low probability data race, so KCSAN might be hard-pressed to spot it. Anyway, the result in much much nicer with the converged use of the ->cpu_no_qs.b.exp field, so thank you!!! Might simplify a few of your future headlamp diagrams as well? ;-) Thanx, Paul > Thanks, > Frederic > --- > > Frederic Weisbecker (4): > rcu: Ignore rdp.cpu_no_qs.b.exp on premptible RCU's rcu_qs() > rcu: Remove useless WRITE_ONCE() on rcu_data.exp_deferred_qs > rcu: Move rcu_data.cpu_no_qs.b.exp reset to rcu_export_exp_rdp() > rcu: Remove rcu_data.exp_deferred_qs and convert to rcu_data.cpu no_qs.b.exp > > > kernel/rcu/tree.h | 1 - > kernel/rcu/tree_exp.h | 6 +++--- > kernel/rcu/tree_plugin.h | 24 +++++++++++++----------- > 3 files changed, 16 insertions(+), 15 deletions(-)
