Re: [PATCH 1/2] lockdep: Don't disable interrupts on RT in disable_irq_nosync_lockdep.*()

[Guenter Roeck]

On Wed, Feb 12, 2025 at 11:36:18AM +0100, Sebastian Andrzej Siewior wrote:
> disable_irq_nosync_lockdep() disables interrupts with lockdep enabled to
> avoid false positive reports by lockdep that a certain lock has not been
> acquired with disabled interrupts. The user of this macros expects that
> a lock can be acquried without disabling interrupts because the IRQ line
> triggering the interrupt is disabled.
> 
> This triggers a warning on PREEMPT_RT because after
> disable_irq_nosync_lockdep.*() the following spinlock_t now is acquired
> with disabled interrupts.
> 
> On PREEMPT_RT there is no difference between spin_lock() and
> spin_lock_irq() so avoiding disabling interrupts in this case works for
> the two remaining callers as of today.
> 
> Don't disable interrupts on PREEMPT_RT in disable_irq_nosync_lockdep.*().
> 
> Reported-by: Guenter Roeck <linux@xxxxxxxxxxxx>
> Closes: https://lore.kernel.org/760e34f9-6034-40e0-82a5-ee9becd24438@xxxxxxxxxxxx
> Fixes: e8106b941ceab ("[PATCH] lockdep: core, add enable/disable_irq_irqsave/irqrestore() APIs")
> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>

Tested-by: Guenter Roeck <linux@xxxxxxxxxxxx>