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# c17ee635 23-Feb-2026 Maxime Ripard <mripard@kernel.org>

Merge drm/drm-fixes into drm-misc-fixes

7.0-rc1 was just released, let's merge it to kick the new release cycle.

Signed-off-by: Maxime Ripard <mripard@kernel.org>


Revision tags: v7.0-rc1
# ef852baa 09-Feb-2026 Linus Torvalds <torvalds@linux-foundation.org>

Merge tag 'rcu.release.v7.0' of git://git.kernel.org/pub/scm/linux/kernel/git/rcu/linux

Pull RCU updates from Boqun Feng:

- RCU Tasks Trace:

Re-implement RCU tasks trace in term of SRCU-fast,

Merge tag 'rcu.release.v7.0' of git://git.kernel.org/pub/scm/linux/kernel/git/rcu/linux

Pull RCU updates from Boqun Feng:

- RCU Tasks Trace:

Re-implement RCU tasks trace in term of SRCU-fast, not only more than
500 lines of code are saved because of the reimplementation, a new
set of API, rcu_read_{,un}lock_tasks_trace(), becomes possible as
well. Compared to the previous rcu_read_{,un}lock_trace(), the new
API avoid the task_struct accesses thanks to the SRCU-fast semantics.

As a result, the old rcu_read{,un}lock_trace() API is now deprecated.

- RCU Torture Test:
- Multiple improvements on kvm-series.sh (parallel run and
progress showing metrics)
- Add context checks to rcu_torture_timer()
- Make config2csv.sh properly handle comments in .boot files
- Include commit discription in testid.txt

- Miscellaneous RCU changes:
- Reduce synchronize_rcu() latency by reporting GP kthread's
CPU QS early
- Use suitable gfp_flags for the init_srcu_struct_nodes()
- Fix rcu_read_unlock() deadloop due to softirq
- Correctly compute probability to invoke ->exp_current()
in rcutorture
- Make expedited RCU CPU stall warnings detect stall-end races

- RCU nocb:
- Remove unnecessary WakeOvfIsDeferred wake path and callback
overload handling
- Extract nocb_defer_wakeup_cancel() helper

* tag 'rcu.release.v7.0' of git://git.kernel.org/pub/scm/linux/kernel/git/rcu/linux: (25 commits)
rcu/nocb: Extract nocb_defer_wakeup_cancel() helper
rcu/nocb: Remove dead callback overload handling
rcu/nocb: Remove unnecessary WakeOvfIsDeferred wake path
rcu: Reduce synchronize_rcu() latency by reporting GP kthread's CPU QS early
srcu: Use suitable gfp_flags for the init_srcu_struct_nodes()
rcu: Fix rcu_read_unlock() deadloop due to softirq
rcutorture: Correctly compute probability to invoke ->exp_current()
rcu: Make expedited RCU CPU stall warnings detect stall-end races
rcutorture: Add --kill-previous option to terminate previous kvm.sh runs
rcutorture: Prevent concurrent kvm.sh runs on same source tree
torture: Include commit discription in testid.txt
torture: Make config2csv.sh properly handle comments in .boot files
torture: Make kvm-series.sh give run numbers and totals
torture: Make kvm-series.sh give build numbers and totals
torture: Parallelize kvm-series.sh guest-OS execution
rcutorture: Add context checks to rcu_torture_timer()
rcutorture: Test rcu_tasks_trace_expedite_current()
srcu: Create an rcu_tasks_trace_expedite_current() function
checkpatch: Deprecate rcu_read_{,un}lock_trace()
rcu: Update Requirements.rst for RCU Tasks Trace
...

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Revision tags: v6.19, v6.19-rc8, v6.19-rc7, v6.19-rc6, v6.19-rc5, v6.19-rc4
# 60908279 04-Jan-2026 Boqun Feng <boqun.feng@gmail.com>

Merge branch 'rcu-tasks-trace.20260101a'

* rcu-tasks-trace.20260101a:
rcutorture: Test rcu_tasks_trace_expedite_current()
srcu: Create an rcu_tasks_trace_expedite_current() function
checkpatch

Merge branch 'rcu-tasks-trace.20260101a'

* rcu-tasks-trace.20260101a:
rcutorture: Test rcu_tasks_trace_expedite_current()
srcu: Create an rcu_tasks_trace_expedite_current() function
checkpatch: Deprecate rcu_read_{,un}lock_trace()
rcu: Update Requirements.rst for RCU Tasks Trace
rcu: Add noinstr-fast rcu_read_{,un}lock_tasks_trace() APIs
rcu: Move rcu_tasks_trace_srcu_struct out of #ifdef CONFIG_TASKS_RCU_GENERIC
rcu: Clean up after the SRCU-fastification of RCU Tasks Trace
context_tracking: Remove rcu_task_trace_heavyweight_{enter,exit}()
rcu: Re-implement RCU Tasks Trace in terms of SRCU-fast

show more ...


# 1a72f4bb 29-Dec-2025 Paul E. McKenney <paulmck@kernel.org>

rcu: Add noinstr-fast rcu_read_{,un}lock_tasks_trace() APIs

When expressing RCU Tasks Trace in terms of SRCU-fast, it was
necessary to keep a nesting count and per-CPU srcu_ctr structure
pointer in

rcu: Add noinstr-fast rcu_read_{,un}lock_tasks_trace() APIs

When expressing RCU Tasks Trace in terms of SRCU-fast, it was
necessary to keep a nesting count and per-CPU srcu_ctr structure
pointer in the task_struct structure, which is slow to access.
But an alternative is to instead make rcu_read_lock_tasks_trace() and
rcu_read_unlock_tasks_trace(), which match the underlying SRCU-fast
semantics, avoiding the task_struct accesses.

When all callers have switched to the new API, the previous
rcu_read_lock_trace() and rcu_read_unlock_trace() APIs will be removed.

The rcu_read_{,un}lock_{,tasks_}trace() functions need to use smp_mb()
only if invoked where RCU is not watching, that is, from locations where
a call to rcu_is_watching() would return false. In architectures that
define the ARCH_WANTS_NO_INSTR Kconfig option, use of noinstr and friends
ensures that tracing happens only where RCU is watching, so those
architectures can dispense entirely with the read-side calls to smp_mb().

Other architectures include these read-side calls by default, but in many
installations there might be either larger than average tolerance for
risk, prohibition of removing tracing on a running system, or careful
review and approval of removing of tracing. Such installations can
build their kernels with CONFIG_TASKS_TRACE_RCU_NO_MB=y to avoid those
read-side calls to smp_mb(), thus accepting responsibility for run-time
removal of tracing from code regions that RCU is not watching.

Those wishing to disable read-side memory barriers for an entire
architecture can select this TASKS_TRACE_RCU_NO_MB Kconfig option,
hence the polarity.

[ paulmck: Apply Peter Zijlstra feedback. ]

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Cc: Andrii Nakryiko <andrii@kernel.org>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: bpf@vger.kernel.org
Reviewed-by: Joel Fernandes <joelagnelf@nvidia.com>
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>

show more ...


# 176a6aea 29-Dec-2025 Paul E. McKenney <paulmck@kernel.org>

rcu: Move rcu_tasks_trace_srcu_struct out of #ifdef CONFIG_TASKS_RCU_GENERIC

Moving the rcu_tasks_trace_srcu_struct structure instance out
from under the CONFIG_TASKS_RCU_GENERIC Kconfig option perm

rcu: Move rcu_tasks_trace_srcu_struct out of #ifdef CONFIG_TASKS_RCU_GENERIC

Moving the rcu_tasks_trace_srcu_struct structure instance out
from under the CONFIG_TASKS_RCU_GENERIC Kconfig option permits
the CONFIG_TASKS_TRACE_RCU Kconfig option to stop enabling this
CONFIG_TASKS_RCU_GENERIC Kconfig option. This commit also therefore
makes it so.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Cc: Andrii Nakryiko <andrii@kernel.org>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: bpf@vger.kernel.org
Reviewed-by: Joel Fernandes <joelagnelf@nvidia.com>
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>

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# a73fc3dc 29-Dec-2025 Paul E. McKenney <paulmck@kernel.org>

rcu: Clean up after the SRCU-fastification of RCU Tasks Trace

Now that RCU Tasks Trace has been re-implemented in terms of SRCU-fast,
the ->trc_ipi_to_cpu, ->trc_blkd_cpu, ->trc_blkd_node, ->trc_hol

rcu: Clean up after the SRCU-fastification of RCU Tasks Trace

Now that RCU Tasks Trace has been re-implemented in terms of SRCU-fast,
the ->trc_ipi_to_cpu, ->trc_blkd_cpu, ->trc_blkd_node, ->trc_holdout_list,
and ->trc_reader_special task_struct fields are no longer used.

In addition, the rcu_tasks_trace_qs(), rcu_tasks_trace_qs_blkd(),
exit_tasks_rcu_finish_trace(), and rcu_spawn_tasks_trace_kthread(),
show_rcu_tasks_trace_gp_kthread(), rcu_tasks_trace_get_gp_data(),
rcu_tasks_trace_torture_stats_print(), and get_rcu_tasks_trace_gp_kthread()
functions and all the other functions that they invoke are no longer used.

Also, the TRC_NEED_QS and TRC_NEED_QS_CHECKED CPP macros are no longer used.
Neither are the rcu_tasks_trace_lazy_ms and rcu_task_ipi_delay rcupdate
module parameters and the TASKS_TRACE_RCU_READ_MB Kconfig option.

This commit therefore removes all of them.

[ paulmck: Apply Alexei Starovoitov feedback. ]

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Cc: Andrii Nakryiko <andrii@kernel.org>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: bpf@vger.kernel.org
Reviewed-by: Joel Fernandes <joelagnelf@nvidia.com>
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>

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Revision tags: v6.19-rc3, v6.19-rc2, v6.19-rc1, v6.18, v6.18-rc7, v6.18-rc6, v6.18-rc5, v6.18-rc4, v6.18-rc3, v6.18-rc2, v6.18-rc1, v6.17, v6.17-rc7, v6.17-rc6, v6.17-rc5, v6.17-rc4, v6.17-rc3, v6.17-rc2, v6.17-rc1, v6.16, v6.16-rc7, v6.16-rc6, v6.16-rc5, v6.16-rc4, v6.16-rc3, v6.16-rc2, v6.16-rc1
# bbfd5594 28-May-2025 Joonas Lahtinen <joonas.lahtinen@linux.intel.com>

Merge drm/drm-next into drm-intel-gt-next

Need to pull in a67221b5eb8d ("drm/i915/dp: Return min bpc supported by source instead of 0")
in order to fix build breakage on GCC 9.4.0 (from Ubuntu 20.04

Merge drm/drm-next into drm-intel-gt-next

Need to pull in a67221b5eb8d ("drm/i915/dp: Return min bpc supported by source instead of 0")
in order to fix build breakage on GCC 9.4.0 (from Ubuntu 20.04).

Signed-off-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>

show more ...


Revision tags: v6.15, v6.15-rc7
# db5302ae 16-May-2025 Jani Nikula <jani.nikula@intel.com>

Merge drm/drm-next into drm-intel-next

Backmerge to sync with v6.15-rc, xe, and specifically async flip changes
in drm-misc.

Signed-off-by: Jani Nikula <jani.nikula@intel.com>


# 4f978603 02-Jun-2025 Dmitry Torokhov <dmitry.torokhov@gmail.com>

Merge branch 'next' into for-linus

Prepare input updates for 6.16 merge window.


# d51b9d81 16-May-2025 Dmitry Torokhov <dmitry.torokhov@gmail.com>

Merge tag 'v6.15-rc6' into next

Sync up with mainline to bring in xpad controller changes.


Revision tags: v6.15-rc6, v6.15-rc5
# 844e31bb 29-Apr-2025 Rob Clark <robdclark@chromium.org>

Merge remote-tracking branch 'drm-misc/drm-misc-next' into msm-next

Merge drm-misc-next to get commit Fixes: fec450ca15af ("drm/display:
hdmi: provide central data authority for ACR params").

Signe

Merge remote-tracking branch 'drm-misc/drm-misc-next' into msm-next

Merge drm-misc-next to get commit Fixes: fec450ca15af ("drm/display:
hdmi: provide central data authority for ACR params").

Signed-off-by: Rob Clark <robdclark@chromium.org>

show more ...


Revision tags: v6.15-rc4
# 3ab7ae8e 24-Apr-2025 Thomas Hellström <thomas.hellstrom@linux.intel.com>

Merge drm/drm-next into drm-xe-next

Backmerge to bring in linux 6.15-rc.

Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>


Revision tags: v6.15-rc3, v6.15-rc2
# 1afba39f 07-Apr-2025 Thomas Zimmermann <tzimmermann@suse.de>

Merge drm/drm-next into drm-misc-next

Backmerging to get v6.15-rc1 into drm-misc-next. Also fixes a
build issue when enabling CONFIG_DRM_SCHED_KUNIT_TEST.

Signed-off-by: Thomas Zimmermann <tzimmerm

Merge drm/drm-next into drm-misc-next

Backmerging to get v6.15-rc1 into drm-misc-next. Also fixes a
build issue when enabling CONFIG_DRM_SCHED_KUNIT_TEST.

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>

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# 9f13acb2 11-Apr-2025 Ingo Molnar <mingo@kernel.org>

Merge tag 'v6.15-rc1' into x86/cpu, to refresh the branch with upstream changes

Signed-off-by: Ingo Molnar <mingo@kernel.org>


# 78a84fbf 09-Apr-2025 Ingo Molnar <mingo@kernel.org>

Merge tag 'v6.15-rc1' into x86/mm, to pick up fixes

Signed-off-by: Ingo Molnar <mingo@kernel.org>


# 6ce0fdaa 09-Apr-2025 Ingo Molnar <mingo@kernel.org>

Merge tag 'v6.15-rc1' into x86/asm, to refresh the branch

Signed-off-by: Ingo Molnar <mingo@kernel.org>


# 1260ed77 08-Apr-2025 Thomas Zimmermann <tzimmermann@suse.de>

Merge drm/drm-fixes into drm-misc-fixes

Backmerging to get updates from v6.15-rc1.

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>


Revision tags: v6.15-rc1
# da0512b2 02-Apr-2025 Linus Torvalds <torvalds@linux-foundation.org>

Merge tag 'rcu-fixes-v6.15' of git://git.kernel.org/pub/scm/linux/kernel/git/rcu/linux

Pull RCU fix from Boqun Feng:

- srcu: Make FORCE_NEED_SRCU_NMI_SAFE depend on RCU_EXPERT

* tag 'rcu-fixes-v6

Merge tag 'rcu-fixes-v6.15' of git://git.kernel.org/pub/scm/linux/kernel/git/rcu/linux

Pull RCU fix from Boqun Feng:

- srcu: Make FORCE_NEED_SRCU_NMI_SAFE depend on RCU_EXPERT

* tag 'rcu-fixes-v6.15' of git://git.kernel.org/pub/scm/linux/kernel/git/rcu/linux:
srcu: Make FORCE_NEED_SRCU_NMI_SAFE depend on RCU_EXPERT

show more ...


# 1dc1e0b9 25-Mar-2025 Paul E. McKenney <paulmck@kernel.org>

srcu: Make FORCE_NEED_SRCU_NMI_SAFE depend on RCU_EXPERT

The FORCE_NEED_SRCU_NMI_SAFE is useful only for those wishing to test
the SRCU code paths that accommodate architectures that do not have
NMI

srcu: Make FORCE_NEED_SRCU_NMI_SAFE depend on RCU_EXPERT

The FORCE_NEED_SRCU_NMI_SAFE is useful only for those wishing to test
the SRCU code paths that accommodate architectures that do not have
NMI-safe per-CPU operations, that is, those architectures that do not
select the ARCH_HAS_NMI_SAFE_THIS_CPU_OPS Kconfig option. As such, this
is a specialized Kconfig option that is not intended for casual users.

This commit therefore hides it behind the RCU_EXPERT Kconfig option.
Given that this new FORCE_NEED_SRCU_NMI_SAFE Kconfig option has no effect
unless the ARCH_HAS_NMI_SAFE_THIS_CPU_OPS Kconfig option is also selected,
it also depends on this Kconfig option.

[ paulmck: Apply Geert Uytterhoeven feedback. ]

[ boqun: Add the "Fixes" tag. ]

Reported-by: Geert Uytterhoeven <geert@linux-m68k.org>
Closes: https://lore.kernel.org/all/CAMuHMdX6dy9_tmpLkpcnGzxyRbe6qSWYukcPp=H1GzZdyd3qBQ@mail.gmail.com/
Fixes: 536e8b9b80bc ("srcu: Add FORCE_NEED_SRCU_NMI_SAFE Kconfig for testing")
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Reviewed-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>

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# 2487b6b9 25-Mar-2025 Ingo Molnar <mingo@kernel.org>

Merge branch 'linus' into x86/urgent, to pick up fixes and refresh the branch

Signed-off-by: Ingo Molnar <mingo@kernel.org>


Revision tags: v6.14, v6.14-rc7, v6.14-rc6, v6.14-rc5, v6.14-rc4, v6.14-rc3, v6.14-rc2
# c771600c 05-Feb-2025 Tvrtko Ursulin <tursulin@ursulin.net>

Merge drm/drm-next into drm-intel-gt-next

We need
4ba4f1afb6a9 ("perf: Generic hotplug support for a PMU with a scope")
in order to land a i915 PMU simplification and a fix. That landed in 6.12
and

Merge drm/drm-next into drm-intel-gt-next

We need
4ba4f1afb6a9 ("perf: Generic hotplug support for a PMU with a scope")
in order to land a i915 PMU simplification and a fix. That landed in 6.12
and we are stuck at 6.9 so lets bump things forward.

Signed-off-by: Tvrtko Ursulin <tursulin@ursulin.net>

show more ...


# 3ba7dfb8 25-Mar-2025 Linus Torvalds <torvalds@linux-foundation.org>

Merge tag 'rcu-next-v6.15' of git://git.kernel.org/pub/scm/linux/kernel/git/rcu/linux

Pull RCU updates from Boqun Feng:
"Documentation:
- Add broken-timing possibility to stallwarn.rst
- Impr

Merge tag 'rcu-next-v6.15' of git://git.kernel.org/pub/scm/linux/kernel/git/rcu/linux

Pull RCU updates from Boqun Feng:
"Documentation:
- Add broken-timing possibility to stallwarn.rst
- Improve discussion of this_cpu_ptr(), add raw_cpu_ptr()
- Document self-propagating callbacks
- Point call_srcu() to call_rcu() for detailed memory ordering
- Add CONFIG_RCU_LAZY delays to call_rcu() kernel-doc header
- Clarify RCU_LAZY and RCU_LAZY_DEFAULT_OFF help text
- Remove references to old grace-period-wait primitives

srcu:
- Introduce srcu_read_{un,}lock_fast(), which is similar to
srcu_read_{un,}lock_lite(): avoid smp_mb()s in lock and unlock
at the cost of calling synchronize_rcu() in synchronize_srcu()

Moreover, by returning the percpu offset of the counter at
srcu_read_lock_fast() time, srcu_read_unlock_fast() can avoid
extra pointer dereferencing, which makes it faster than
srcu_read_{un,}lock_lite()

srcu_read_{un,}lock_fast() are intended to replace
rcu_read_{un,}lock_trace() if possible

RCU torture:
- Add get_torture_init_jiffies() to return the start time of the test
- Add a test_boost_holdoff module parameter to allow delaying
boosting tests when building rcutorture as built-in
- Add grace period sequence number logging at the beginning and end
of failure/close-call results
- Switch to hexadecimal for the expedited grace period sequence
number in the rcu_exp_grace_period trace point
- Make cur_ops->format_gp_seqs take buffer length
- Move RCU_TORTURE_TEST_{CHK_RDR_STATE,LOG_CPU} to bool
- Complain when invalid SRCU reader_flavor is specified
- Add FORCE_NEED_SRCU_NMI_SAFE Kconfig for testing, which forces SRCU
uses atomics even when percpu ops are NMI safe, and use the Kconfig
for SRCU lockdep testing

Misc:
- Split rcu_report_exp_cpu_mult() mask parameter and use for tracing
- Remove READ_ONCE() for rdp->gpwrap access in __note_gp_changes()
- Fix get_state_synchronize_rcu_full() GP-start detection
- Move RCU Tasks self-tests to core_initcall()
- Print segment lengths in show_rcu_nocb_gp_state()
- Make RCU watch ct_kernel_exit_state() warning
- Flush console log from kernel_power_off()
- rcutorture: Allow a negative value for nfakewriters
- rcu: Update TREE05.boot to test normal synchronize_rcu()
- rcu: Use _full() API to debug synchronize_rcu()

Make RCU handle PREEMPT_LAZY better:
- Fix header guard for rcu_all_qs()
- rcu: Rename PREEMPT_AUTO to PREEMPT_LAZY
- Update __cond_resched comment about RCU quiescent states
- Handle unstable rdp in rcu_read_unlock_strict()
- Handle quiescent states for PREEMPT_RCU=n, PREEMPT_COUNT=y
- osnoise: Provide quiescent states
- Adjust rcutorture with possible PREEMPT_RCU=n && PREEMPT_COUNT=y
combination
- Limit PREEMPT_RCU configurations
- Make rcutorture senario TREE07 and senario TREE10 use
PREEMPT_LAZY=y"

* tag 'rcu-next-v6.15' of git://git.kernel.org/pub/scm/linux/kernel/git/rcu/linux: (59 commits)
rcutorture: Make scenario TREE07 build CONFIG_PREEMPT_LAZY=y
rcutorture: Make scenario TREE10 build CONFIG_PREEMPT_LAZY=y
rcu: limit PREEMPT_RCU configurations
rcutorture: Update ->extendables check for lazy preemption
rcutorture: Update rcutorture_one_extend_check() for lazy preemption
osnoise: provide quiescent states
rcu: Use _full() API to debug synchronize_rcu()
rcu: Update TREE05.boot to test normal synchronize_rcu()
rcutorture: Allow a negative value for nfakewriters
Flush console log from kernel_power_off()
context_tracking: Make RCU watch ct_kernel_exit_state() warning
rcu/nocb: Print segment lengths in show_rcu_nocb_gp_state()
rcu-tasks: Move RCU Tasks self-tests to core_initcall()
rcu: Fix get_state_synchronize_rcu_full() GP-start detection
torture: Make SRCU lockdep testing use srcu_read_lock_nmisafe()
srcu: Add FORCE_NEED_SRCU_NMI_SAFE Kconfig for testing
rcutorture: Complain when invalid SRCU reader_flavor is specified
rcutorture: Move RCU_TORTURE_TEST_{CHK_RDR_STATE,LOG_CPU} to bool
rcutorture: Make cur_ops->format_gp_seqs take buffer length
rcutorture: Add ftrace-compatible timestamp to GP# failure/close-call output
...

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# 467c890f 05-Mar-2025 Boqun Feng <boqun.feng@gmail.com>

Merge branches 'docs.2025.02.04a', 'lazypreempt.2025.03.04a', 'misc.2025.03.04a', 'srcu.2025.02.05a' and 'torture.2025.02.05a'


Revision tags: v6.14-rc1, v6.13, v6.13-rc7, v6.13-rc6, v6.13-rc5, v6.13-rc4, v6.13-rc3
# 8437bb84 13-Dec-2024 Ankur Arora <ankur.a.arora@oracle.com>

rcu: limit PREEMPT_RCU configurations

PREEMPT_LAZY can be enabled stand-alone or alongside PREEMPT_DYNAMIC
which allows for dynamic switching of preemption models.

The choice of PREEMPT_RCU or not,

rcu: limit PREEMPT_RCU configurations

PREEMPT_LAZY can be enabled stand-alone or alongside PREEMPT_DYNAMIC
which allows for dynamic switching of preemption models.

The choice of PREEMPT_RCU or not, however, is fixed at compile time.

Given that PREEMPT_RCU makes some trade-offs to optimize for latency
as opposed to throughput, configurations with limited preemption
might prefer the stronger forward-progress guarantees of PREEMPT_RCU=n.

Accordingly, explicitly limit PREEMPT_RCU=y to the latency oriented
preemption models: PREEMPT, PREEMPT_RT, and the runtime configurable
model PREEMPT_DYNAMIC.

This means the throughput oriented models, PREEMPT_NONE,
PREEMPT_VOLUNTARY, and PREEMPT_LAZY will run with PREEMPT_RCU=n.

Cc: Paul E. McKenney <paulmck@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Ankur Arora <ankur.a.arora@oracle.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>

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# 536e8b9b 10-Jan-2025 Paul E. McKenney <paulmck@kernel.org>

srcu: Add FORCE_NEED_SRCU_NMI_SAFE Kconfig for testing

The srcu_read_lock_nmisafe() and srcu_read_unlock_nmisafe() functions
map to __srcu_read_lock() and __srcu_read_unlock() on systems like x86
th

srcu: Add FORCE_NEED_SRCU_NMI_SAFE Kconfig for testing

The srcu_read_lock_nmisafe() and srcu_read_unlock_nmisafe() functions
map to __srcu_read_lock() and __srcu_read_unlock() on systems like x86
that have NMI-safe this_cpu_inc() operations. This makes the underlying
__srcu_read_lock_nmisafe() and __srcu_read_unlock_nmisafe() functions
difficult to test on (for example) x86 systems, allowing bugs to creep in.

This commit therefore creates a FORCE_NEED_SRCU_NMI_SAFE Kconfig that
forces those underlying functions to be used even on systems where they
are not needed, thus providing better testing coverage.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>

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