linux-toradex.git/kernel/rcu, branch v6.16-rc6

rcu: Return early if callback is not specified

2025-06-20T19:31:48+00:00

Currently the call_rcu() API does not check whether a callback
pointer is NULL. If NULL is passed, rcu_core() will try to invoke
it, resulting in NULL pointer dereference and a kernel crash.

To prevent this and improve debuggability, this patch adds a check
for NULL and emits a kernel stack trace to help identify a faulty
caller.

Signed-off-by: Uladzislau Rezki (Sony) 
Reviewed-by: Joel Fernandes 
Signed-off-by: Joel Fernandes

treewide, timers: Rename from_timer() to timer_container_of()

2025-06-08T07:07:37+00:00

Move this API to the canonical timer_*() namespace.

[ tglx: Redone against pre rc1 ]

Signed-off-by: Ingo Molnar 
Signed-off-by: Thomas Gleixner 
Link: https://lore.kernel.org/all/aB2X0jCKQO56WdMt@gmail.com

kernel/rcu/tree_stall: add /sys/kernel/rcu_stall_count

2025-06-06T05:02:25+00:00

Expose a simple counter to userspace for monitoring tools.

(akpm: 2536c5c7d6ae added the documentation but the code changes were lost)

Link: https://lkml.kernel.org/r/20250504180831.4190860-3-max.kellermann@ionos.com
Fixes: 2536c5c7d6ae ("kernel/rcu/tree_stall: add /sys/kernel/rcu_stall_count")
Signed-off-by: Max Kellermann 
Cc: Core Minyard 
Cc: Doug Anderson 
Cc: Joel Granados 
Cc: Max Kellermann 
Cc: Song Liu 
Cc: Sourabh Jain 
Signed-off-by: Andrew Morton

Merge tag 'timers-cleanups-2025-05-25' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2025-05-27T15:31:21+00:00

Pull timer cleanups from Thomas Gleixner:
 "Another set of timer API cleanups:

    - Convert init_timer*(), try_to_del_timer_sync() and
      destroy_timer_on_stack() over to the canonical timer_*()
      namespace convention.

  There is another large conversion pending, which has not been included
  because it would have caused a gazillion of merge conflicts in next.
  The conversion scripts will be run towards the end of the merge window
  and a pull request sent once all conflict dependencies have been
  merged"

* tag 'timers-cleanups-2025-05-25' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  treewide, timers: Rename destroy_timer_on_stack() as timer_destroy_on_stack()
  treewide, timers: Rename try_to_del_timer_sync() as timer_delete_sync_try()
  timers: Rename init_timers() as timers_init()
  timers: Rename NEXT_TIMER_MAX_DELTA as TIMER_NEXT_MAX_DELTA
  timers: Rename __init_timer_on_stack() as __timer_init_on_stack()
  timers: Rename __init_timer() as __timer_init()
  timers: Rename init_timer_on_stack_key() as timer_init_key_on_stack()
  timers: Rename init_timer_key() as timer_init_key()

Merge branches 'rcu/misc-for-6.16', 'rcu/seq-counters-for-6.16' and 'rcu/torture-for-6.16' into rcu/for-next

2025-05-16T15:18:16+00:00

rcutorture: Perform more frequent testing of ->gpwrap

2025-05-16T15:13:27+00:00

Currently, the ->gpwrap is not tested (at all per my testing) due to the
requirement of a large delta between a CPU's rdp->gp_seq and its node's
rnp->gpseq.

This results in no testing of ->gpwrap being set. This patch by default
adds 5 minutes of testing with ->gpwrap forced by lowering the delta
between rdp->gp_seq and rnp->gp_seq to just 8 GPs. All of this is
configurable, including the active time for the setting and a full
testing cycle.

By default, the first 25 minutes of a test will have the _default_
behavior there is right now (ULONG_MAX / 4) delta. Then for 5 minutes,
we switch to a smaller delta causing 1-2 wraps in 5 minutes. I believe
this is reasonable since we at least add a little bit of testing for
usecases where ->gpwrap is set.

[ Apply fix for Dan Carpenter's bug report on init path cleanup. ]
[ Apply kernel doc warning fix from Akira Yokosawa. ]

Tested-by: Paul E. McKenney 
Signed-off-by: Joel Fernandes

rcutorture: Comment invocations of tick_dep_set_task()

2025-05-16T15:12:26+00:00

The rcu_torture_reader() and rcu_torture_fwd_prog_cr() functions
run CPU-bound for extended periods of time (tens or even
hundreds of milliseconds), so they invoke tick_dep_set_task() and
tick_dep_clear_task() to ensure that the scheduling-clock tick helps
move grace periods forward.

So why doesn't rcu_torture_fwd_prog_nr() also invoke tick_dep_set_task()
and tick_dep_clear_task()?  Because the point of this function is to test
RCU's ability to (eventually) force grace periods forward even when the
tick has been disabled during long CPU-bound kernel execution.

Signed-off-by: Paul E. McKenney 
Signed-off-by: Joel Fernandes

rcu/nocb: Add Safe checks for access offloaded rdp

2025-05-16T13:00:54+00:00

For built with CONFIG_PROVE_RCU=y and CONFIG_PREEMPT_RT=y kernels,
Disable BH does not change the SOFTIRQ corresponding bits in
preempt_count(), but change current->softirq_disable_cnt, this
resulted in the following splat:

WARNING: suspicious RCU usage
kernel/rcu/tree_plugin.h:36 Unsafe read of RCU_NOCB offloaded state!
stack backtrace:
CPU: 0 UID: 0 PID: 22 Comm: rcuc/0
Call Trace:
[    0.407907]  
[    0.407910]  dump_stack_lvl+0xbb/0xd0
[    0.407917]  dump_stack+0x14/0x20
[    0.407920]  lockdep_rcu_suspicious+0x133/0x210
[    0.407932]  rcu_rdp_is_offloaded+0x1c3/0x270
[    0.407939]  rcu_core+0x471/0x900
[    0.407942]  ? lockdep_hardirqs_on+0xd5/0x160
[    0.407954]  rcu_cpu_kthread+0x25f/0x870
[    0.407959]  ? __pfx_rcu_cpu_kthread+0x10/0x10
[    0.407966]  smpboot_thread_fn+0x34c/0xa50
[    0.407970]  ? trace_preempt_on+0x54/0x120
[    0.407977]  ? __pfx_smpboot_thread_fn+0x10/0x10
[    0.407982]  kthread+0x40e/0x840
[    0.407990]  ? __pfx_kthread+0x10/0x10
[    0.407994]  ? rt_spin_unlock+0x4e/0xb0
[    0.407997]  ? rt_spin_unlock+0x4e/0xb0
[    0.408000]  ? __pfx_kthread+0x10/0x10
[    0.408006]  ? __pfx_kthread+0x10/0x10
[    0.408011]  ret_from_fork+0x40/0x70
[    0.408013]  ? __pfx_kthread+0x10/0x10
[    0.408018]  ret_from_fork_asm+0x1a/0x30
[    0.408042]  

Currently, triggering an rdp offloaded state change need the
corresponding rdp's CPU goes offline, and at this time the rcuc
kthreads has already in parking state. this means the corresponding
rcuc kthreads can safely read offloaded state of rdp while it's
corresponding cpu is online.

This commit therefore add softirq_count() check for
Preempt-RT kernels.

Suggested-by: Joel Fernandes 
Reviewed-by: Frederic Weisbecker 
Signed-off-by: Zqiang 
Signed-off-by: Joel Fernandes

rcuscale: using kcalloc() to relpace kmalloc()

2025-05-16T13:00:54+00:00

It's safer to using kcalloc() because it can prevent overflow
problem.

Reviewed-by: Paul E. McKenney 
Signed-off-by: Su Hui 
Signed-off-by: Joel Fernandes

Revert "rcu/nocb: Fix rcuog wake-up from offline softirq"

2025-05-16T13:00:54+00:00

This reverts commit f7345ccc62a4b880cf76458db5f320725f28e400.

swake_up_one_online() has been removed because hrtimers can now assign
a proper online target to hrtimers queued from offline CPUs. Therefore
remove the related hackery.

Link: https://lore.kernel.org/all/20241231170712.149394-4-frederic@kernel.org/
Reviewed-by: Usama Arif 
Reviewed-by: Joel Fernandes 
Signed-off-by: Frederic Weisbecker 
Signed-off-by: Joel Fernandes