On Fri, Sep 11, 2026 at 12:21:52PM +0200, Sebastian Andrzej Siewior wrote:
> rb_wake_up_waiters() is a irq_work callback which is initialized with
> init_irq_work(). As such it will be invoked in thread context on
> PREEMPT_RT. Invoking the callback in IRQ context on PREEMPT_RT is not an
> option due its usage of wake_up_all().
> Since this callback may run in thread context, it needs to acqurie
nit: typo "acquire"
> ring_buffer_per_cpu::reader_lock with disabling interrupts and may not
> assume that they are disabled.
>
> Use raw_spinlock_irqsave() to acquire ring_buffer_per_cpu::reader_lock.
>
> Fixes: 68282dd930ea3 ("ring-buffer: Fix resetting of shortest_full")
> Signed-off-by: Sebastian Andrzej Siewior <[email protected]>
> ---
> kernel/trace/ring_buffer.c | 13 ++++++-------
> 1 file changed, 6 insertions(+), 7 deletions(-)
>
> diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
> index 9c03a555a6ba2..681f9daf6fabb 100644
> --- a/kernel/trace/ring_buffer.c
> +++ b/kernel/trace/ring_buffer.c
> @@ -904,14 +904,13 @@ static void rb_wake_up_waiters(struct irq_work *work)
> struct ring_buffer_per_cpu *cpu_buffer =
> container_of(rbwork, struct ring_buffer_per_cpu,
> irq_work);
>
> - /* Called from interrupt context */
> - raw_spin_lock(&cpu_buffer->reader_lock);
> - rbwork->wakeup_full = false;
> - rbwork->full_waiters_pending = false;
> + scoped_guard(raw_spinlock_irqsave, &cpu_buffer->reader_lock) {
> + rbwork->wakeup_full = false;
> + rbwork->full_waiters_pending = false;
>
> - /* Waking up all waiters, they will reset the shortest full */
> - cpu_buffer->shortest_full = 0;
> - raw_spin_unlock(&cpu_buffer->reader_lock);
> + /* Waking up all waiters, they will reset the shortest
> full */
> + cpu_buffer->shortest_full = 0;
> + }
>
> wake_up_all(&rbwork->full_waiters);
> }
> --
> 2.55.0
>
>
Reviewed-by: Vincent Donnefort <[email protected]>
