On 2025-02-14 17:27:39 [+0100], Vlastimil Babka wrote: > From: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx> > > 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. spin_trylock() is not safe due to explicit locking in the underneath rt_spin_trylock() implementation. Removing this explicit locking and attempting only "trylock" is undesired due to PI implications. > Note there is no need to use local_inc for acquired variable, > since it's a percpu variable with strict nesting scopes. > > Signed-off-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx> > Signed-off-by: Alexei Starovoitov <ast@xxxxxxxxxx> > Signed-off-by: Vlastimil Babka <vbabka@xxxxxxx> Other than that, thank you two ;) Sebastian
