Re: [PATCH v8 06/21] printk: nbcon: Synchronise console unregistration against atomic flushers

[Petr Mladek]

On Fri 2025-11-28 03:43:32, Chris Down wrote:
> The nbcon atomic flush path in __nbcon_atomic_flush_pending_con() calls
> nbcon_emit_next_record(), which uses console_srcu_read_flags() to read
> the console flags. console_srcu_read_flags() expects to be called under
> console_srcu_read_lock(), but the atomic flush path does not hold this
> lock.

__nbcon_atomic_flush_pending_con() seems to be called in the following
code paths:

  + __nbcon_atomic_flush_pending()
    + nbcon_atomic_flush_pending_con()
      + __nbcon_atomic_flush_pending_con()

 + nbcon_device_release()
   + __nbcon_atomic_flush_pending_con()

 + kdb_msg_write()		# new in 6.19-rc1
   + nbcon_kdb_release()
     + __nbcon_atomic_flush_pending_con()

And all three callers take console_srcu_read_lock() because
they need it for other reasons. So, we should be on the safe
side and do not need this change.

Or do I miss some code path, please?

Best Regards,
Petr