linux-stable.git/kernel/sched/ext.c, branch linux-6.17.y Linux kernel stable tree sched_ext: Use IRQ_WORK_INIT_HARD() to initialize rq->scx.kick_cpus_irq_work 2025-12-12T17:40:22+00:00 Zqiang qiang.zhang@linux.dev 2025-11-17T12:53:10+00:00 9a92af96baf52640d60353ed948421950d23618a [ Upstream commit 36c6f3c03d104faf1aa90922f2310549c175420f ] For PREEMPT_RT kernels, the kick_cpus_irq_workfn() be invoked in the per-cpu irq_work/* task context and there is no rcu-read critical section to protect. this commit therefore use IRQ_WORK_INIT_HARD() to initialize the per-cpu rq->scx.kick_cpus_irq_work in the init_sched_ext_class(). Signed-off-by: Zqiang <qiang.zhang@linux.dev> Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Sasha Levin <sashal@kernel.org> 
[ Upstream commit 36c6f3c03d104faf1aa90922f2310549c175420f ]

For PREEMPT_RT kernels, the kick_cpus_irq_workfn() be invoked in
the per-cpu irq_work/* task context and there is no rcu-read critical
section to protect. this commit therefore use IRQ_WORK_INIT_HARD() to
initialize the per-cpu rq->scx.kick_cpus_irq_work in the
init_sched_ext_class().

Signed-off-by: Zqiang <qiang.zhang@linux.dev>
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
sched_ext: Fix possible deadlock in the deferred_irq_workfn() 2025-12-12T17:40:22+00:00 Zqiang qiang.zhang@linux.dev 2025-11-13T11:43:55+00:00 600b4379b9a7ba41340d652211fb29699da4c629 [ Upstream commit a257e974210320ede524f340ffe16bf4bf0dda1e ] For PREEMPT_RT=y kernels, the deferred_irq_workfn() is executed in the per-cpu irq_work/* task context and not disable-irq, if the rq returned by container_of() is current CPU's rq, the following scenarios may occur: lock(&rq->__lock); <Interrupt> lock(&rq->__lock); This commit use IRQ_WORK_INIT_HARD() to replace init_irq_work() to initialize rq->scx.deferred_irq_work, make the deferred_irq_workfn() is always invoked in hard-irq context. Signed-off-by: Zqiang <qiang.zhang@linux.dev> Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Sasha Levin <sashal@kernel.org> 
[ Upstream commit a257e974210320ede524f340ffe16bf4bf0dda1e ]

For PREEMPT_RT=y kernels, the deferred_irq_workfn() is executed in
the per-cpu irq_work/* task context and not disable-irq, if the rq
returned by container_of() is current CPU's rq, the following scenarios
may occur:

lock(&rq->__lock);
<Interrupt>
  lock(&rq->__lock);

This commit use IRQ_WORK_INIT_HARD() to replace init_irq_work() to
initialize rq->scx.deferred_irq_work, make the deferred_irq_workfn()
is always invoked in hard-irq context.

Signed-off-by: Zqiang <qiang.zhang@linux.dev>
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
sched_ext: fix flag check for deferred callbacks 2025-12-01T10:46:08+00:00 Emil Tsalapatis etsal@meta.com 2025-10-16T18:11:26+00:00 4a4abb0f9660de9f9336e3880249d5ea918cbabb commit a3c4a0a42e61aad1056a3d33fd603c1ae66d4288 upstream. When scheduling the deferred balance callbacks, check SCX_RQ_BAL_CB_PENDING instead of SCX_RQ_BAL_PENDING. This way schedule_deferred() properly tests whether there is already a pending request for queue_balance_callback() to be invoked at the end of .balance(). Fixes: a8ad873113d3 ("sched_ext: defer queue_balance_callback() until after ops.dispatch") Signed-off-by: Emil Tsalapatis <emil@etsalapatis.com> Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
commit a3c4a0a42e61aad1056a3d33fd603c1ae66d4288 upstream.

When scheduling the deferred balance callbacks, check SCX_RQ_BAL_CB_PENDING
instead of SCX_RQ_BAL_PENDING. This way schedule_deferred() properly tests
whether there is already a pending request for queue_balance_callback() to
be invoked at the end of .balance().

Fixes: a8ad873113d3 ("sched_ext: defer queue_balance_callback() until after ops.dispatch")
Signed-off-by: Emil Tsalapatis <emil@etsalapatis.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
sched_ext: Fix scx_kick_pseqs corruption on concurrent scheduler loads 2025-12-01T10:46:08+00:00 Andrea Righi arighi@nvidia.com 2025-10-13T20:36:34+00:00 18228a70a01a49e34fe599ccacc88a2bca70dce2 commit 05e63305c85c88141500f0a2fb02afcfba9396e1 upstream. If we load a BPF scheduler while another scheduler is already running, alloc_kick_pseqs() would be called again, overwriting the previously allocated arrays. Fix by moving the alloc_kick_pseqs() call after the scx_enable_state() check, ensuring that the arrays are only allocated when a scheduler can actually be loaded. Fixes: 14c1da3895a11 ("sched_ext: Allocate scx_kick_cpus_pnt_seqs lazily using kvzalloc()") Signed-off-by: Andrea Righi <arighi@nvidia.com> Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
commit 05e63305c85c88141500f0a2fb02afcfba9396e1 upstream.

If we load a BPF scheduler while another scheduler is already running,
alloc_kick_pseqs() would be called again, overwriting the previously
allocated arrays.

Fix by moving the alloc_kick_pseqs() call after the scx_enable_state()
check, ensuring that the arrays are only allocated when a scheduler can
actually be loaded.

Fixes: 14c1da3895a11 ("sched_ext: Allocate scx_kick_cpus_pnt_seqs lazily using kvzalloc()")
Signed-off-by: Andrea Righi <arighi@nvidia.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
sched_ext: defer queue_balance_callback() until after ops.dispatch 2025-12-01T10:46:01+00:00 Emil Tsalapatis etsal@meta.com 2025-10-10T19:12:50+00:00 f39659da573a8df319d428d5e26e5da7b2b62f46 [ Upstream commit a8ad873113d3fe01f9b5d737d4b0570fa36826b0 ] The sched_ext code calls queue_balance_callback() during enqueue_task() to defer operations that drop multiple locks until we can unpin them. The call assumes that the rq lock is held until the callbacks are invoked, and the pending callbacks will not be visible to any other threads. This is enforced by a WARN_ON_ONCE() in rq_pin_lock(). However, balance_one() may actually drop the lock during a BPF dispatch call. Another thread may win the race to get the rq lock and see the pending callback. To avoid this, sched_ext must only queue the callback after the dispatch calls have completed. CPU 0 CPU 1 CPU 2 scx_balance() rq_unpin_lock() scx_balance_one() |= IN_BALANCE scx_enqueue() ops.dispatch() rq_unlock() rq_lock() queue_balance_callback() rq_unlock() [WARN] rq_pin_lock() rq_lock() &= ~IN_BALANCE rq_repin_lock() Changelog v2-> v1 (https://lore.kernel.org/sched-ext/aOgOxtHCeyRT_7jn@gpd4) - Fixed explanation in patch description (Andrea) - Fixed scx_rq mask state updates (Andrea) - Added Reviewed-by tag from Andrea Reported-by: Jakub Kicinski <kuba@kernel.org> Signed-off-by: Emil Tsalapatis (Meta) <emil@etsalapatis.com> Reviewed-by: Andrea Righi <arighi@nvidia.com> Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Sasha Levin <sashal@kernel.org> 
[ Upstream commit a8ad873113d3fe01f9b5d737d4b0570fa36826b0 ]

The sched_ext code calls queue_balance_callback() during enqueue_task()
to defer operations that drop multiple locks until we can unpin them.
The call assumes that the rq lock is held until the callbacks are
invoked, and the pending callbacks will not be visible to any other
threads. This is enforced by a WARN_ON_ONCE() in rq_pin_lock().

However, balance_one() may actually drop the lock during a BPF dispatch
call. Another thread may win the race to get the rq lock and see the
pending callback. To avoid this, sched_ext must only queue the callback
after the dispatch calls have completed.

CPU 0                   CPU 1           CPU 2

scx_balance()
  rq_unpin_lock()
  scx_balance_one()
    |= IN_BALANCE	scx_enqueue()
    ops.dispatch()
      rq_unlock()
                        rq_lock()
                        queue_balance_callback()
                        rq_unlock()
                                        [WARN] rq_pin_lock()
      rq_lock()
    &= ~IN_BALANCE
rq_repin_lock()

Changelog

v2-> v1 (https://lore.kernel.org/sched-ext/aOgOxtHCeyRT_7jn@gpd4)

- Fixed explanation in patch description (Andrea)
- Fixed scx_rq mask state updates (Andrea)
- Added Reviewed-by tag from Andrea

Reported-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Emil Tsalapatis (Meta) <emil@etsalapatis.com>
Reviewed-by: Andrea Righi <arighi@nvidia.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
sched_ext: Allocate scx_kick_cpus_pnt_seqs lazily using kvzalloc() 2025-12-01T10:46:01+00:00 Tejun Heo tj@kernel.org 2025-10-08T23:43:26+00:00 15e2041a97ed58a0d156a36a29ec3b0a8a8db9b9 [ Upstream commit 14c1da3895a116f4e32c20487046655f26d3999b ] On systems with >4096 CPUs, scx_kick_cpus_pnt_seqs allocation fails during boot because it exceeds the 32,768 byte percpu allocator limit. Restructure to use DEFINE_PER_CPU() for the per-CPU pointers, with each CPU pointing to its own kvzalloc'd array. Move allocation from boot time to scx_enable() and free in scx_disable(), so the O(nr_cpu_ids^2) memory is only consumed when sched_ext is active. Use RCU to guard against racing with free. Arrays are freed via call_rcu() and kick_cpus_irq_workfn() uses rcu_dereference_bh() with a NULL check. While at it, rename to scx_kick_pseqs for brevity and update comments to clarify these are pick_task sequence numbers. v2: RCU protect scx_kick_seqs to manage kick_cpus_irq_workfn() racing against disable as per Andrea. v3: Fix bugs notcied by Andrea. Reported-by: Phil Auld <pauld@redhat.com> Link: http://lkml.kernel.org/r/20251007133523.GA93086@pauld.westford.csb Cc: Andrea Righi <arighi@nvidia.com> Reviewed-by: Emil Tsalapatis <emil@etsalapatis.com> Reviewed-by: Phil Auld <pauld@redhat.com> Reviewed-by: Andrea Righi <arighi@nvidia.com> Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Sasha Levin <sashal@kernel.org> 
[ Upstream commit 14c1da3895a116f4e32c20487046655f26d3999b ]

On systems with >4096 CPUs, scx_kick_cpus_pnt_seqs allocation fails during
boot because it exceeds the 32,768 byte percpu allocator limit.

Restructure to use DEFINE_PER_CPU() for the per-CPU pointers, with each CPU
pointing to its own kvzalloc'd array. Move allocation from boot time to
scx_enable() and free in scx_disable(), so the O(nr_cpu_ids^2) memory is only
consumed when sched_ext is active.

Use RCU to guard against racing with free. Arrays are freed via call_rcu()
and kick_cpus_irq_workfn() uses rcu_dereference_bh() with a NULL check.

While at it, rename to scx_kick_pseqs for brevity and update comments to
clarify these are pick_task sequence numbers.

v2: RCU protect scx_kick_seqs to manage kick_cpus_irq_workfn() racing
    against disable as per Andrea.

v3: Fix bugs notcied by Andrea.

Reported-by: Phil Auld <pauld@redhat.com>
Link: http://lkml.kernel.org/r/20251007133523.GA93086@pauld.westford.csb
Cc: Andrea Righi <arighi@nvidia.com>
Reviewed-by: Emil Tsalapatis <emil@etsalapatis.com>
Reviewed-by: Phil Auld <pauld@redhat.com>
Reviewed-by: Andrea Righi <arighi@nvidia.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
sched_ext: Fix scx_enable() crash on helper kthread creation failure 2025-12-01T10:45:42+00:00 Saket Kumar Bhaskar skb99@linux.ibm.com 2025-11-19T10:37:22+00:00 625e173e2a59b6cf6cbfb51c0a6bea47f3861eab commit 7b6216baae751369195fa3c83d434d23bcda406a upstream. A crash was observed when the sched_ext selftests runner was terminated with Ctrl+\ while test 15 was running: NIP [c00000000028fa58] scx_enable.constprop.0+0x358/0x12b0 LR [c00000000028fa2c] scx_enable.constprop.0+0x32c/0x12b0 Call Trace: scx_enable.constprop.0+0x32c/0x12b0 (unreliable) bpf_struct_ops_link_create+0x18c/0x22c __sys_bpf+0x23f8/0x3044 sys_bpf+0x2c/0x6c system_call_exception+0x124/0x320 system_call_vectored_common+0x15c/0x2ec kthread_run_worker() returns an ERR_PTR() on failure rather than NULL, but the current code in scx_alloc_and_add_sched() only checks for a NULL helper. Incase of failure on SIGQUIT, the error is not handled in scx_alloc_and_add_sched() and scx_enable() ends up dereferencing an error pointer. Error handling is fixed in scx_alloc_and_add_sched() to propagate PTR_ERR() into ret, so that scx_enable() jumps to the existing error path, avoiding random dereference on failure. Fixes: bff3b5aec1b7 ("sched_ext: Move disable machinery into scx_sched") Cc: stable@vger.kernel.org # v6.16+ Reported-and-tested-by: Samir Mulani <samir@linux.ibm.com> Signed-off-by: Saket Kumar Bhaskar <skb99@linux.ibm.com> Reviewed-by: Emil Tsalapatis <emil@etsalapatis.com> Reviewed-by: Andrea Righi <arighi@nvidia.com> Reviewed-by: Vishal Chourasia <vishalc@linux.ibm.com> Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
commit 7b6216baae751369195fa3c83d434d23bcda406a upstream.

A crash was observed when the sched_ext selftests runner was
terminated with Ctrl+\ while test 15 was running:

NIP [c00000000028fa58] scx_enable.constprop.0+0x358/0x12b0
LR [c00000000028fa2c] scx_enable.constprop.0+0x32c/0x12b0
Call Trace:
scx_enable.constprop.0+0x32c/0x12b0 (unreliable)
bpf_struct_ops_link_create+0x18c/0x22c
__sys_bpf+0x23f8/0x3044
sys_bpf+0x2c/0x6c
system_call_exception+0x124/0x320
system_call_vectored_common+0x15c/0x2ec

kthread_run_worker() returns an ERR_PTR() on failure rather than NULL,
but the current code in scx_alloc_and_add_sched() only checks for a NULL
helper. Incase of failure on SIGQUIT, the error is not handled in
scx_alloc_and_add_sched() and scx_enable() ends up dereferencing an
error pointer.

Error handling is fixed in scx_alloc_and_add_sched() to propagate
PTR_ERR() into ret, so that scx_enable() jumps to the existing error
path, avoiding random dereference on failure.

Fixes: bff3b5aec1b7 ("sched_ext: Move disable machinery into scx_sched")
Cc: stable@vger.kernel.org # v6.16+
Reported-and-tested-by: Samir Mulani <samir@linux.ibm.com>
Signed-off-by: Saket Kumar Bhaskar <skb99@linux.ibm.com>
Reviewed-by: Emil Tsalapatis <emil@etsalapatis.com>
Reviewed-by: Andrea Righi <arighi@nvidia.com>
Reviewed-by: Vishal Chourasia <vishalc@linux.ibm.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
sched_ext: Fix unsafe locking in the scx_dump_state() 2025-11-24T09:37:37+00:00 Zqiang qiang.zhang@linux.dev 2025-11-12T07:33:28+00:00 b6109750063d3b9aca1c57031213ac5485a06c54 [ Upstream commit 5f02151c411dda46efcc5dc57b0845efcdcfc26d ] For built with CONFIG_PREEMPT_RT=y kernels, the dump_lock will be converted sleepable spinlock and not disable-irq, so the following scenarios occur: inconsistent {IN-HARDIRQ-W} -> {HARDIRQ-ON-W} usage. irq_work/0/27 [HC0[0]:SC0[0]:HE1:SE1] takes: (&rq->__lock){?...}-{2:2}, at: raw_spin_rq_lock_nested+0x2b/0x40 {IN-HARDIRQ-W} state was registered at: lock_acquire+0x1e1/0x510 _raw_spin_lock_nested+0x42/0x80 raw_spin_rq_lock_nested+0x2b/0x40 sched_tick+0xae/0x7b0 update_process_times+0x14c/0x1b0 tick_periodic+0x62/0x1f0 tick_handle_periodic+0x48/0xf0 timer_interrupt+0x55/0x80 __handle_irq_event_percpu+0x20a/0x5c0 handle_irq_event_percpu+0x18/0xc0 handle_irq_event+0xb5/0x150 handle_level_irq+0x220/0x460 __common_interrupt+0xa2/0x1e0 common_interrupt+0xb0/0xd0 asm_common_interrupt+0x2b/0x40 _raw_spin_unlock_irqrestore+0x45/0x80 __setup_irq+0xc34/0x1a30 request_threaded_irq+0x214/0x2f0 hpet_time_init+0x3e/0x60 x86_late_time_init+0x5b/0xb0 start_kernel+0x308/0x410 x86_64_start_reservations+0x1c/0x30 x86_64_start_kernel+0x96/0xa0 common_startup_64+0x13e/0x148 other info that might help us debug this: Possible unsafe locking scenario: CPU0 ---- lock(&rq->__lock); <Interrupt> lock(&rq->__lock); *** DEADLOCK *** stack backtrace: CPU: 0 UID: 0 PID: 27 Comm: irq_work/0 Call Trace: <TASK> dump_stack_lvl+0x8c/0xd0 dump_stack+0x14/0x20 print_usage_bug+0x42e/0x690 mark_lock.part.44+0x867/0xa70 ? __pfx_mark_lock.part.44+0x10/0x10 ? string_nocheck+0x19c/0x310 ? number+0x739/0x9f0 ? __pfx_string_nocheck+0x10/0x10 ? __pfx_check_pointer+0x10/0x10 ? kvm_sched_clock_read+0x15/0x30 ? sched_clock_noinstr+0xd/0x20 ? local_clock_noinstr+0x1c/0xe0 __lock_acquire+0xc4b/0x62b0 ? __pfx_format_decode+0x10/0x10 ? __pfx_string+0x10/0x10 ? __pfx___lock_acquire+0x10/0x10 ? __pfx_vsnprintf+0x10/0x10 lock_acquire+0x1e1/0x510 ? raw_spin_rq_lock_nested+0x2b/0x40 ? __pfx_lock_acquire+0x10/0x10 ? dump_line+0x12e/0x270 ? raw_spin_rq_lock_nested+0x20/0x40 _raw_spin_lock_nested+0x42/0x80 ? raw_spin_rq_lock_nested+0x2b/0x40 raw_spin_rq_lock_nested+0x2b/0x40 scx_dump_state+0x3b3/0x1270 ? finish_task_switch+0x27e/0x840 scx_ops_error_irq_workfn+0x67/0x80 irq_work_single+0x113/0x260 irq_work_run_list.part.3+0x44/0x70 run_irq_workd+0x6b/0x90 ? __pfx_run_irq_workd+0x10/0x10 smpboot_thread_fn+0x529/0x870 ? __pfx_smpboot_thread_fn+0x10/0x10 kthread+0x305/0x3f0 ? __pfx_kthread+0x10/0x10 ret_from_fork+0x40/0x70 ? __pfx_kthread+0x10/0x10 ret_from_fork_asm+0x1a/0x30 </TASK> This commit therefore use rq_lock_irqsave/irqrestore() to replace rq_lock/unlock() in the scx_dump_state(). Fixes: 07814a9439a3 ("sched_ext: Print debug dump after an error exit") Signed-off-by: Zqiang <qiang.zhang@linux.dev> Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Sasha Levin <sashal@kernel.org> 
[ Upstream commit 5f02151c411dda46efcc5dc57b0845efcdcfc26d ]

For built with CONFIG_PREEMPT_RT=y kernels, the dump_lock will be converted
sleepable spinlock and not disable-irq, so the following scenarios occur:

inconsistent {IN-HARDIRQ-W} -> {HARDIRQ-ON-W} usage.
irq_work/0/27 [HC0[0]:SC0[0]:HE1:SE1] takes:
(&rq->__lock){?...}-{2:2}, at: raw_spin_rq_lock_nested+0x2b/0x40
{IN-HARDIRQ-W} state was registered at:
   lock_acquire+0x1e1/0x510
   _raw_spin_lock_nested+0x42/0x80
   raw_spin_rq_lock_nested+0x2b/0x40
   sched_tick+0xae/0x7b0
   update_process_times+0x14c/0x1b0
   tick_periodic+0x62/0x1f0
   tick_handle_periodic+0x48/0xf0
   timer_interrupt+0x55/0x80
   __handle_irq_event_percpu+0x20a/0x5c0
   handle_irq_event_percpu+0x18/0xc0
   handle_irq_event+0xb5/0x150
   handle_level_irq+0x220/0x460
   __common_interrupt+0xa2/0x1e0
   common_interrupt+0xb0/0xd0
   asm_common_interrupt+0x2b/0x40
   _raw_spin_unlock_irqrestore+0x45/0x80
   __setup_irq+0xc34/0x1a30
   request_threaded_irq+0x214/0x2f0
   hpet_time_init+0x3e/0x60
   x86_late_time_init+0x5b/0xb0
   start_kernel+0x308/0x410
   x86_64_start_reservations+0x1c/0x30
   x86_64_start_kernel+0x96/0xa0
   common_startup_64+0x13e/0x148

 other info that might help us debug this:
 Possible unsafe locking scenario:

        CPU0
        ----
   lock(&rq->__lock);
   <Interrupt>
     lock(&rq->__lock);

  *** DEADLOCK ***

 stack backtrace:
 CPU: 0 UID: 0 PID: 27 Comm: irq_work/0
 Call Trace:
  <TASK>
  dump_stack_lvl+0x8c/0xd0
  dump_stack+0x14/0x20
  print_usage_bug+0x42e/0x690
  mark_lock.part.44+0x867/0xa70
  ? __pfx_mark_lock.part.44+0x10/0x10
  ? string_nocheck+0x19c/0x310
  ? number+0x739/0x9f0
  ? __pfx_string_nocheck+0x10/0x10
  ? __pfx_check_pointer+0x10/0x10
  ? kvm_sched_clock_read+0x15/0x30
  ? sched_clock_noinstr+0xd/0x20
  ? local_clock_noinstr+0x1c/0xe0
  __lock_acquire+0xc4b/0x62b0
  ? __pfx_format_decode+0x10/0x10
  ? __pfx_string+0x10/0x10
  ? __pfx___lock_acquire+0x10/0x10
  ? __pfx_vsnprintf+0x10/0x10
  lock_acquire+0x1e1/0x510
  ? raw_spin_rq_lock_nested+0x2b/0x40
  ? __pfx_lock_acquire+0x10/0x10
  ? dump_line+0x12e/0x270
  ? raw_spin_rq_lock_nested+0x20/0x40
  _raw_spin_lock_nested+0x42/0x80
  ? raw_spin_rq_lock_nested+0x2b/0x40
  raw_spin_rq_lock_nested+0x2b/0x40
  scx_dump_state+0x3b3/0x1270
  ? finish_task_switch+0x27e/0x840
  scx_ops_error_irq_workfn+0x67/0x80
  irq_work_single+0x113/0x260
  irq_work_run_list.part.3+0x44/0x70
  run_irq_workd+0x6b/0x90
  ? __pfx_run_irq_workd+0x10/0x10
  smpboot_thread_fn+0x529/0x870
  ? __pfx_smpboot_thread_fn+0x10/0x10
  kthread+0x305/0x3f0
  ? __pfx_kthread+0x10/0x10
  ret_from_fork+0x40/0x70
  ? __pfx_kthread+0x10/0x10
  ret_from_fork_asm+0x1a/0x30
  </TASK>

This commit therefore use rq_lock_irqsave/irqrestore() to replace
rq_lock/unlock() in the scx_dump_state().

Fixes: 07814a9439a3 ("sched_ext: Print debug dump after an error exit")
Signed-off-by: Zqiang <qiang.zhang@linux.dev>
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
sched_ext: Mark scx_bpf_dsq_move_set_[slice|vtime]() with KF_RCU 2025-11-13T20:36:36+00:00 Tejun Heo tj@kernel.org 2025-10-07T01:35:36+00:00 ef215ad4081e8c74dd80895447037d3deac7edfb commit 54e96258a6930909b690fd7e8889749231ba8085 upstream. scx_bpf_dsq_move_set_slice() and scx_bpf_dsq_move_set_vtime() take a DSQ iterator argument which has to be valid. Mark them with KF_RCU. Fixes: 4c30f5ce4f7a ("sched_ext: Implement scx_bpf_dispatch[_vtime]_from_dsq()") Cc: stable@vger.kernel.org # v6.12+ Acked-by: Andrea Righi <arighi@nvidia.com> Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
commit 54e96258a6930909b690fd7e8889749231ba8085 upstream.

scx_bpf_dsq_move_set_slice() and scx_bpf_dsq_move_set_vtime() take a DSQ
iterator argument which has to be valid. Mark them with KF_RCU.

Fixes: 4c30f5ce4f7a ("sched_ext: Implement scx_bpf_dispatch[_vtime]_from_dsq()")
Cc: stable@vger.kernel.org # v6.12+
Acked-by: Andrea Righi <arighi@nvidia.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
sched_ext: Keep bypass on between enable failure and scx_disable_workfn() 2025-11-02T13:18:03+00:00 Tejun Heo tj@kernel.org 2025-09-03T21:33:28+00:00 09a75f371298a7142ad2eb0af04a571d4cf57e50 [ Upstream commit 4a1d9d73aabc8f97f48c4f84f936de3b265ffd6f ] scx_enable() turns on the bypass mode while enable is in progress. If enabling fails, it turns off the bypass mode and then triggers scx_error(). scx_error() will trigger scx_disable_workfn() which will turn on the bypass mode again and unload the failed scheduler. This moves the system out of bypass mode between the enable error path and the disable path, which is unnecessary and can be brittle - e.g. the thread running scx_enable() may already be on the failed scheduler and can be switched out before it triggers scx_error() leading to a stall. The watchdog would eventually kick in, so the situation isn't critical but is still suboptimal. There is nothing to be gained by turning off the bypass mode between scx_enable() failure and scx_disable_workfn(). Keep bypass on. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Andrea Righi <arighi@nvidia.com> Signed-off-by: Sasha Levin <sashal@kernel.org> 
[ Upstream commit 4a1d9d73aabc8f97f48c4f84f936de3b265ffd6f ]

scx_enable() turns on the bypass mode while enable is in progress. If
enabling fails, it turns off the bypass mode and then triggers scx_error().
scx_error() will trigger scx_disable_workfn() which will turn on the bypass
mode again and unload the failed scheduler.

This moves the system out of bypass mode between the enable error path and
the disable path, which is unnecessary and can be brittle - e.g. the thread
running scx_enable() may already be on the failed scheduler and can be
switched out before it triggers scx_error() leading to a stall. The watchdog
would eventually kick in, so the situation isn't critical but is still
suboptimal.

There is nothing to be gained by turning off the bypass mode between
scx_enable() failure and scx_disable_workfn(). Keep bypass on.

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Andrea Righi <arighi@nvidia.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>