Re: [RFC V2 12/21] rv/reactor: Add the printk reactor

[John Ogness <john.ogness@xxxxxxxxxxxxx>]

On 2022-02-14, Daniel Bristot de Oliveira <bristot@xxxxxxxxxx> wrote:
> On 2/14/22 18:25, Shuah Khan wrote:
>> On 2/14/22 3:45 AM, Daniel Bristot de Oliveira wrote:
>>> Note: do not use this reactor with rq_lock taken, it will lock the
>>> system until printk can handle that.
>> 
>> Please give more details on "lock the system" and how locking
>> would impact users and system operation
>
> It is a deadlock on the rq_lock. Hopefully the new printk
> implementation handles that better.

I suggest using printk_deferred() for this reactor for now. With
printk_deferred() the message and timestamp are immediately and
locklessly stored in the buffer, and the printing is performed in a
separate context. printk_deferred() is safe for all contexts.

John