On Fri, 14 Feb 2025, Vlastimil Babka wrote:
From: Sebastian Andrzej Siewior <bige...@linutronix.de>
In !PREEMPT_RT local_lock_irqsave() disables interrupts to protect
critical section, but it doesn't prevent NMI, so the fully reentrant
code cannot use local_lock_irqsave() for exclusive access.
Introduce localtry_lock_t and localtry_lock_irqsave() that
disables interrupts and sets acquired=1, so localtry_lock_irqsave()
from NMI attempting to acquire the same lock will return false.
In PREEMPT_RT local_lock_irqsave() maps to preemptible spin_lock().
Map localtry_lock_irqsave() to preemptible spin_trylock().
When in hard IRQ or NMI return false right away, since
spin_trylock() is not safe due to PI issues.
Note there is no need to use local_inc for acquired variable,
since it's a percpu variable with strict nesting scopes.
LGTM.
Acked-by: Davidlohr Bueso <d...@stgolabs.net>
