Re: [PATCH printk v3 19/19] printk: Avoid false positive lockdep report for legacy printing

[Petr Mladek <pmladek@suse.com>]

On Mon 2024-07-22 19:25:39, John Ogness wrote:
> Legacy console printing from printk() caller context may invoke
> the console driver from atomic context. This leads to a lockdep
> splat because the console driver will acquire a sleeping lock
> and the caller may already hold a spinning lock. This is noticed
> by lockdep on !PREEMPT_RT configurations because it will lead to
> a problem on PREEMPT_RT.
> 
> However, on PREEMPT_RT the printing path from atomic context is
> always avoided and the console driver is always invoked from a
> dedicated thread. Thus the lockdep splat on !PREEMPT_RT is a
> false positive.
> 
> For !PREEMPT_RT override the lock-context before invoking the
> console driver to avoid the false positive.
> 
> Do not override the lock-context for PREEMPT_RT in order to
> allow lockdep to catch any real locking context issues related
> to the write callback usage.
> 
> Signed-off-by: John Ogness <john.ogness@linutronix.de>

Makes sense:

Reviewed-by: Petr Mladek <pmladek@suse.com>

Best Regards,
Petr