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Subject[PATCH 0/5] hvc_console updates was Re: [BUG] hvc_console WARN() on current upstream
Date
Alan Cox wrote:
> Benjamin Herrenschmidt wrote:
>> Seems that we are in interrupt, doing hvc_poll, which does
>> tty_flip_buffer_push
>
>Which means that someone has tty->low_latency set and is calling
>tty_flip_buffer_push in an IRQ. That has never been allowed or safe, and
>now it hurts ;)
>
>/**
> * tty_flip_buffer_push - terminal
> * @tty: tty to push
> *
> * Queue a push of the terminal flip buffers to the line discipline.
>This
> * function must not be called from IRQ context if tty->low_latency
>is set *
> * In the event of the queue being busy for flipping the work will be
> * held off and retried later.
> *
> * Locking: tty buffer lock. Driver locks in low latency mode.
> */
>
>
>That comment has been there for some years in varying formats
>

I actually was preparing a patch for this problem after I had encountered
the a deadlock due to this. That is in the first patch. I then found
and made a few more cleanups, although I might have reordered the rest.

The history for setting low_latency is in the changelog of the first patch..

milton


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