Re: Is it possible to implement interrupt time printk's reliably?

[Andrew Morton]

Jon Smirl <jonsmirl@xxxxxxxxx> wrote:
>
> 
> --- Andrew Morton <akpm@xxxxxxxx> wrote:
> > Jon Smirl <jonsmirl@xxxxxxxxx> wrote:
> > >
> > > > If you're in process context you can use acquire_console_sem(), which will
> > > > serialise against printk.
> > > > 
> > > 
> > > Won't I deadlock if I have acquire_console_sem(), take an interrupt, and
> > then a
> > > printk is issued from the interrupt handelr?
> > > 
> > 
> > Nope.  If printk finds the semaphore to be held it queues up the characters
> > and returns without printing them.  The console_sem-holding process will
> > print the newly buffered characters before releasing the semaphore.
> 
> Is this solution sufficient for kernel developers wanting to use printk from
> interrupt handlers? I've gotten negative feedback from Linus when I suggested
> queuing them before.
> 

It has been this way for several years.
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