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There is rt_mutex_{pre|post}_schedule() around
rt_mutex_wait_proxy_lock() to ensure that sched_submit_work()/
sched_update_worker() is invoked before we schedule out and block on
rt_mutex while waiting for it become available.
The reason is that blocking on rt_mutex assigns a pi_waiter for the PI
chain and sched_submit_work() will also assign a pi_waiter if it blocks
on lock but a this point we already have a waiter assigned.
We can't skip sched_submit_work() entirely because I/O relies on the
fact that I/O queue is flushed while it blocks on a sleeping lock.
Therefore sched_submit_work() is moved before we block on the lock.
Sleeping lock in this context means mutex or rw_semaphore not spinlock_t
on PREEMPT_RT. Because the mutex abstraction on PREEMPT_RT uses the same
abstraction as the futex proxy lock, the futex code ended up using
rt_mutex_{pre|post}_schedule(), too.
Using it is/ was just to keep the task_struct::sched_rt_mutex assertion
happy. Futex proxy lock is used only in the syscall context of a task.
At this point it never got any I/O that needs to be flushed and it can't
be a workqueue that needs to notify that it will be scheduled out.
Therefore sched_submit_work() does nothing here.
By mistake futex_wait_requeue_pi() -> rt_mutex_wait_proxy_lock() did not
get the rt_mutex_{pre|post}_schedule() annotation. This was not noticed
because in this callchain the lock is (usually) not contended and so
rt_mutex_slowlock_block() does not schedule, triggering the assert.
Adding rt_mutex_pre_schedule() here looks wrong (as noted by PeterZ)
because at this point there is a pi_waiter recorded and invoking
sched_submit_work() with a possible lock contention would be wrong.
Add rt_mutex_futex_{pre|post}_schedule() which toggles the
sched_rt_mutex assert and does not involve sched_submit_work(). Add
asserts here to ensure that sched_submit_work() would do nothing. Use it
only in futex proxy lock case which is rt_mutex_wait_proxy_lock().
Remove it from futex_lock_pi().
Fixes: d14f9e930b90 ("locking/rtmutex: Use rt_mutex specific scheduler helpers")
Reported-by: Yao Kai <yaokai34@huawei.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/20260901135453.3121948-2-bigeasy@linutronix.de
Closes: https://lore.kernel.org/all/20260717084922.4153317-2-yaokai34@huawei.com
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It turns out the previous usage of hardirq_disable_count() in
__irq_exit_rcu() would cause softirq pending issues. Without that usage,
hardirq_disable_count() doesn't need to exist, so remove it.
Also move hardirq_disable_enter/exit() into the Rust specific interrupt_rc
header.
[ tglx: Move the helpers over ]
Signed-off-by: Boqun Feng <boqun@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Link: https://patch.msgid.link/20260827194835.38968-1-boqun@kernel.org
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Currently a softirq may be pending longer then expected if the
triggering interrupt happens in-between hardirq_disable_enter() and
_local_interrupt_disable() in local_interrupt_disable():
local_interrupt_disable():
hardirq_disable_enter();
<interrupt>
...
__irq_exit_rcu():
// false because hardirq_disable_count() is not 0
if (.. && !hardirq_disable_count() && ..) {
invoke_softirq();
}
_local_interrupt_disable();
, it'll defer the softirq to the next interrupt which can be forever.
The order between hardirq_disable_enter() and _local_interrupt_disable()
is to optimize re-disabling interrupts if they are already disabled, but
as 1) local_interrupt_disable() is not widely used yet and 2) the proper
way to achieve this optimization may need fixing up the counter at
entry/exit time [1], so reverse the order for now to avoid the softirq
pending issue.
Because of this fix, the part of saving the current state is separated
from irq disabling, and the logic of local_interrupt_disable() becomes:
local_irq_save(flags);
if (counter++ == 0) {
this_cpu(local_interrupt_disable_state) = flags;
}
Therefore change the helper function _local_interrupt_disable() to
_local_interrupt_save_state() which only saves the current irqflags
(when interrupts get disabled the first time).
Fixes: e901c1510e24 ("irq,spin_lock: Add counted interrupt disabling/enabling")
Reported-by: Thomas Gleixner <tglx@kernel.org>
Signed-off-by: Boqun Feng <boqun@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Reviewed-by: Bradley Morgan <brads@mainlining.org>
Link: https://patch.msgid.link/20260829213412.14303-1-boqun@kernel.org
Link: https://lore.kernel.org/lkml/87v78wezid.ffs@fw13/ [1]
Closes: https://lore.kernel.org/lkml/87jypbfu1t.ffs@fw13/
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Revert commit 1b0866874833 ("locking: Switch to _irq_{disable,enable}()
variants in cleanup guards").
While the guards are properly nested, not all wrapped code is nice, as already
highlighted by that fair.c hunk.
Syzbot found another instance of this pattern in posix_timer_delete(), which
does spin_unlock_irq()+spin_lock_irq() inside scoped_guard(spinlock_irq).
Combined with this patch, that goes sideways most spectacular.
Undo this until we've developed stronger tools / debug for such issues.
Fixes: 1b0866874833 ("locking: Switch to _irq_{disable,enable}() variants in cleanup guards")
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://patch.msgid.link/20260824105523.GA4121620%40noisy.programming.kicks-ass.net
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git://git.kernel.org/pub/scm/linux/kernel/git/rcu/linux
Pull RCU updates from Paul McKenney:
"Make expedited grace periods expedite normal RCU callbacks
Miscellaneous fixes:
- Improve diagnostic output with character task states
- Mark accesses to inform KCSAN of concurrency design
- Move from kmalloc() to kmalloc_obj()
- Documentation updates
- Improve handling of RCU deferred quiescent states
- Clean up unused function arguments and structure fields
- Reduce show_rcu_gp_kthreads() stack space
Tasks RCU updates:
- Clean up after SRCU re-implementation of Tasks Trace RCU
- Mark accesses to inform KCSAN of concurrency design
- Add ->lazy_timer status to diagnostic output
- Remove an unnecessary memory barrier
- Fix a data race, courtesy of KCSAN
- Documentation updates
- Convert cond_resched_tasks_rcu_qs() from macro to static inline
function
SRCU updates:
- Add Rust helpers for SRCU
- Avoid losing queued work at cleanup_srcu_struct() time
Torture-test updates:
- Preparation work for immediate RCU priority deboosting
- Test RCU readers from real interrupt handlers (as opposed to
softirq)
- Simplify code through use of cpumask_next_wrap()
- Improve diagnostic output with character task states
- Add rcutorture.nwriters parameter to allow lightweight stall
testing, and rcutorture.stall_only to make doing so easier
- Test an RCU Tasks Trace grace period implying an RCU grace period
- Make RCU Tasks Trace torturing track reader batches
- Fix a data race, courtesy of KCSAN
- Plug a shuffle_tmp_mask memory leak on kthread spawn failure"
* tag 'rcu.2026.08.18a' of git://git.kernel.org/pub/scm/linux/kernel/git/rcu/linux: (59 commits)
rcu: Add closing parenthesis in comment in rcu_read_unlock_strict()
rcutorture: Make {,s}rcu_read_delay() better handle forward-progress testing
rcutorture: Announce declining to forward-progress test
torture: Don't leak shuffle_tmp_mask when shuffler kthread fails to start
rcutorture: Use this_cpu_inc() for rcu_torture_count[] and rcu_torture_batch[]
rcutorture: Make RCU Tasks Trace track Reader Batches
rcutorture: Test RCU Tasks Trace GP implying RCU GP
rcutorture: Add a stall_only module parameter
rcutorture: Add nwriters module parameter
rcutorture: Use task_state_to_char() for task-state reporting
rcutorture: Use cpumask_next_wrap() in rcu_torture_preempt()
rcutorture: Test RCU readers from hardware interrupt handlers
rcutorture: Check for immediate deboosting at reader end
srcu: Queue sdp->work when the delay timer is successfully deleted
rcu-tasks: Convert cond_resched_tasks_rcu_qs() to static inline
rcu-tasks: Fix some comments for call_rcu_tasks() and call_rcu_tasks_rude()
rcu-tasks: Rename tasks_rcu_exit_srcu_stall_timer to tasks_rcu_exit_stall_timer
rcu: Mark interrupts-enabled accesses to rdp->cpu_no_qs.s
rcu: Reduce stack usage in show_rcu_gp_kthreads()
rcu: Mark accesses to ->rcu_urgent_qs and ->rcu_need_heavy_qs
...
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git://git.kernel.org/pub/scm/linux/kernel/git/i3c/linux
Pull I3C updates from Alexandre Belloni:
"A new driver this cycle, for the AMD AXI I3C controller.
There are also new features such as IBI wakeup support, SETAASA device
discovery and ACPI support for the the DAA methods, meaning we can now
communicate with the SPD devices on DDR5 modules.
New driver:
- AMD AXI I3C master controller
Subsystem:
- I3C Common Command Code (CCC) handling improvements, especially
around GET CCCs
- SETAASA device discovery support
- ACPI support for all existing DAA methods like SETDASA, SETNEWDA as
well as I2C devices on I3C bus
- IBI-based wakeup support
Drivers:
- dw: SETAASA support
- mipi-i3c-hci: advertise IBI wakeup capability, AMD_PT I3C
controller support, PIO queue management support for HCI v1.2
- renesas: improve suspend to RAM support, add runtime PM support"
* tag 'i3c/for-7.3' of git://git.kernel.org/pub/scm/linux/kernel/git/i3c/linux: (70 commits)
i3c: dw: reduce do_daa time if there's no client
i3c: mipi-i3c-hci: Add support for AMD_PT I3C controller
i3c: mipi-i3c-hci: Add PIO queue management support for HCI v1.2
i3c: mipi-i3c-hci: Fix missing STAT_IBI_STATUS_THLD in PIO mode
i3c: dw: rename "pclk" to "apb" to match dt-binding
i3c: dw: make struct dw_i3c_cmd smaller
i3c: dw: use COMMAND_PORT_TRANSFER_ARG instead of hardcoding
i3c: renesas: Don't register devices when ENTDAA times out
i3c: master: dw-i3c-master: fix OD timing for first broadcast
i3c: mipi-i3c-hci: Advertise IBI wakeup capability
i3c: mipi-i3c-hci: Factor out i3c_hci_sysdev()
i3c: mipi-i3c-hci-pci: Propagate I3C wakeup requirements to PCI
i3c: master: Reject IBI requests from non-IBI-capable devices
i3c: master: Add helper to query bus wakeup requirements
i3c: master: Report wakeup events for IBIs
i3c: master: Support IBI-based wakeup capability
i3c: master: Fix potential UAF in i3c_device_match()
i3c: master: Fix potential UAF in i3c_device_uevent()
i3c: Make dev->desc locking assumptions explicit
i3c: master: Fix use-after-free of master->this
...
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'rcu-tasks.2026.07.30a', 'srcu.2026.08.11a' and 'torture.2026.08.14a' into HEAD
Changes:
Make expedited grace periods expedite normal RCU callbacks
Miscellaneous fixes:
* Improve diagnostic output with character task states.
* Mark accesses to inform KCSAN of concurrency design.
* Move from kmalloc() to kmalloc_obj().
* Documentation updates.
* Improve handling of RCU deferred quiescent states.
* Clean up unused function arguments and structure fields.
* Reduce show_rcu_gp_kthreads() stack space.
Tasks RCU updates:
* Clean up after SRCU re-implementation of Tasks Trace RCU.
* Mark accesses to inform KCSAN of concurrency design.
* Add ->lazy_timer status to diagnostic output.
* Remove an unnecessary memory barrier.
* Fix a data race, courtesy of KCSAN.
* Documentation updates.
* Convert cond_resched_tasks_rcu_qs() from macro to static inline
function.
SRCU updates:
* Add Rust helpers for SRCU.
* Avoid losing queued work at cleanup_srcu_struct() time.
Torture-test updates:
* Preparation work for immediate RCU priority deboosting.
* Test RCU readers from real interrupt handlers (as opposed to softirq).
* Simplify code through use of cpumask_next_wrap().
* Improve diagnostic output with character task states.
* Add rcutorture.nwriters parameter to allow lightweight stall testing,
and rcutorture.stall_only to make doing so easier.
* Test an RCU Tasks Trace grace period implying an RCU grace period.
* Make RCU Tasks Trace torturing track reader batches.
* Fix a data race, courtesy of KCSAN.
* Plug a shuffle_tmp_mask memory leak on kthread spawn failure.
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