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

[Daniel Bristot de Oliveira <bristot@xxxxxxxxxx>]

On 2/15/22 11:03, John Ogness wrote:
> 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.

Question: Does it always postpone or only postpone when in a particular
contexts, like, with irqs disabled?

-- Daniel

> John