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Message-ID: <7fa58961-2dce-4e08-8174-1d1cc592210f@paulmck-laptop>
Date: Wed, 1 Oct 2025 07:48:17 -0700
From: "Paul E. McKenney" <paulmck@...nel.org>
To: rcu@...r.kernel.org
Cc: linux-kernel@...r.kernel.org, kernel-team@...a.com, rostedt@...dmis.org,
andrii@...nel.org, ast@...nel.org, peterz@...radead.org,
bpf@...r.kernel.org
Subject: [PATCH v2 0/21] Implement RCU Tasks Trace in terms of SRCU-fast and
optimize
Hello!
This v2 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. It also removes a conditional branch from the
srcu_read_lock_fast() implementation in order to make SRCU-fast a bit
more fastpath-friendly. The patches are as follows:
1. Permit Tiny SRCU srcu_read_unlock() with interrupts disabled.
2. Re-implement RCU Tasks Trace in terms of SRCU-fast.
3. context_tracking: Remove
rcu_task_trace_heavyweight_{enter,exit}().
4. Clean up after the SRCU-fastification of RCU Tasks Trace.
5. Move rcu_tasks_trace_srcu_struct out of #ifdef
CONFIG_TASKS_RCU_GENERIC.
6. Create an srcu_expedite_current() function.
7. Test srcu_expedite_current().
8. Add noinstr-fast rcu_read_{,un}lock_tasks_trace() APIs.
9. Update Requirements.rst for RCU Tasks Trace.
10. Deprecate rcu_read_{,un}lock_trace().
11. Create a DEFINE_SRCU_FAST().
12. Create an rcu_tasks_trace_expedite_current() function.
13. Test rcu_tasks_trace_expedite_current().
14. Make grace-period determination use ssp->srcu_reader_flavor.
15. Exercise DEFINE_STATIC_SRCU_FAST() and init_srcu_struct_fast().
16. Exercise DEFINE_STATIC_SRCU_FAST() and init_srcu_struct_fast().
17. Require special srcu_struct define/init for SRCU-fast readers.
18. Make SRCU-fast readers enforce use of SRCU-fast definition/init.
19. Update for SRCU-fast definitions and initialization.
20. Guard __DECLARE_TRACE() use of __DO_TRACE_CALL() with SRCU-fast.
21. Mark diagnostic functions as notrace.
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
------------------------------------------------------------------------
Documentation/RCU/Design/Requirements/Requirements.rst | 33
b/Documentation/RCU/Design/Requirements/Requirements.rst | 12
b/Documentation/RCU/checklist.rst | 12
b/Documentation/RCU/whatisRCU.rst | 3
b/Documentation/admin-guide/kernel-parameters.txt | 15
b/include/linux/notifier.h | 2
b/include/linux/rcupdate.h | 31
b/include/linux/rcupdate_trace.h | 107 +-
b/include/linux/sched.h | 1
b/include/linux/srcu.h | 16
b/include/linux/srcutiny.h | 1
b/include/linux/srcutree.h | 8
b/include/linux/tracepoint.h | 45 -
b/include/trace/perf.h | 4
b/include/trace/trace_events.h | 4
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/refscale.c | 9
b/kernel/rcu/srcutiny.c | 13
b/kernel/rcu/srcutree.c | 58 +
b/kernel/rcu/tasks.h | 617 ---------------
b/kernel/rcu/tree.c | 2
b/kernel/rcu/update.c | 8
b/kernel/tracepoint.c | 21
b/scripts/checkpatch.pl | 2
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
include/linux/srcu.h | 40
include/linux/srcutiny.h | 14
include/linux/srcutree.h | 50 -
kernel/rcu/Kconfig | 25
kernel/rcu/rcutorture.c | 32
kernel/rcu/srcutree.c | 39
kernel/rcu/tasks.h | 129 ---
41 files changed, 525 insertions(+), 978 deletions(-)
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