6.12-stable review patch. If anyone has any objections, please let me know.
------------------
From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
commit 815e07c8fe885a87751c2496a30ae0dcd4118210 upstream.
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 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.
Cc: <redacted>
Link: https://patch.msgid.link/20260911102152.YEtwkBj9@linutronix.de (local)
Fixes: 68282dd930ea3 ("ring-buffer: Fix resetting of shortest_full")
Reviewed-by: Vincent Donnefort <vdonnefort@google.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
kernel/trace/ring_buffer.c | 13 ++++++-------
1 file changed, 6 insertions(+), 7 deletions(-)
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -837,14 +837,13 @@ static void rb_wake_up_waiters(struct ir
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);
}