On Tue, Dec 30, 2025 at 06:19:11PM -0500, Joel Fernandes wrote:
> On Mon, Dec 29, 2025 at 11:10:55AM -0800, Paul E. McKenney wrote:
> > Hello!
> >
> > This v4 patch series re-implements RCU Tasks Trace in terms of SRCU-fast,
> > reducing the size of the Linux-kernel RCU implementation by several
> > hundred lines of code. The patches are as follows:
> >
> > 1. Re-implement RCU Tasks Trace in terms of SRCU-fast.
> >
> > 2. context_tracking: Remove
> > rcu_task_trace_heavyweight_{enter,exit}().
> >
> > 3. Clean up after the SRCU-fastification of RCU Tasks Trace.
> >
> > 4. Move rcu_tasks_trace_srcu_struct out of #ifdef
> > CONFIG_TASKS_RCU_GENERIC.
> >
> > 5. Add noinstr-fast rcu_read_{,un}lock_tasks_trace() APIs.
> >
> > 6. Update Requirements.rst for RCU Tasks Trace.
> >
> > 7. Deprecate rcu_read_{,un}lock_trace().
> >
> > 8. Create an rcu_tasks_trace_expedite_current() function.
> >
> > 9. Test rcu_tasks_trace_expedite_current().
> >
> > Changes since v3:
> >
> > o Rebase onto v6.19-rc1.
> >
> > o Wait for arm64 per-CPU variable speedups to reach mainline.
> >
> > https://lore.kernel.org/all/a1e505e4-931b-45cf-8ca7-337442aa598e@paulmck-laptop/#r
> >
> > Changes since v2:
> >
> > o SRCU improvments not strictly related to RCU tasks trace have
> > been moved out to a separate series.
> >
> > o Use the new DEFINE_SRCU_FAST().
> >
> > https://lore.kernel.org/all/7fa58961-2dce-4e08-8174-1d1cc592210f@paulmck-laptop/
> >
> > Changes since v1:
> >
> > o Consolidate RCU Tasks Trace cleanup patches per Alexei Starovoitov
> > feedback. This explains the decrease from 34 patches in v1 to
> > only 21 in this v2 series.
> >
> > o While consolidating, consolidate the noinstr-fast patches and the
> > DEFINE_SRCU_FAST()/init_srcu_struct_fast() patches.
> >
> > o Upgrade comments per Peter Zijlstra feedback.
> >
> > o Extract Tiny SRCU bug fix into its own commit per Andrii Nakryiko
> > feedback.
> >
> > o Switch srcu_expedite_current() from preempt_disable() to
> > migrate_disable() for PREEMPT_RT kernels per Zqiang feedback.
> >
> > o Apply tags.
> >
> > https://lore.kernel.org/all/580ea2de-799a-4ddc-bde9-c16f3fb1e6e7@paulmck-laptop/
> >
> > Thanx, Paul
> >
> > ------------------------------------------------------------------------
> >
> > b/Documentation/RCU/Design/Requirements/Requirements.rst | 12
> > b/Documentation/admin-guide/kernel-parameters.txt | 15
> > b/include/linux/rcupdate.h | 31
> > b/include/linux/rcupdate_trace.h | 107 +-
> > b/include/linux/sched.h | 1
> > b/init/init_task.c | 3
> > b/kernel/context_tracking.c | 20
> > b/kernel/fork.c | 3
> > b/kernel/rcu/Kconfig | 18
> > b/kernel/rcu/rcu.h | 9
> > b/kernel/rcu/rcuscale.c | 7
> > b/kernel/rcu/rcutorture.c | 2
> > b/kernel/rcu/tasks.h | 621 ---------------
> > b/scripts/checkpatch.pl | 4
> > b/tools/testing/selftests/rcutorture/configs/rcu/TRACE01 | 1
> > b/tools/testing/selftests/rcutorture/configs/rcu/TRACE02 | 1
> > include/linux/rcupdate_trace.h | 81 +
> > include/linux/sched.h | 5
> > kernel/rcu/Kconfig | 25
> > kernel/rcu/rcutorture.c | 1
> > kernel/rcu/tasks.h | 121 --
> > 21 files changed, 219 insertions(+), 869 deletions(-)
>
> Reviewed-by: Joel Fernandes <joelagnelf@nvidia.com>
>
Queued, thank you both!
Regards,
Boqun
> thanks
>
>