Re: [PATCH] Xen: Force non-irq keyhandler to be run in tasklet when receive a debugkey from serial port

[Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>]

On Mon, Oct 24, 2016 at 09:29:53PM +0800, Lan, Tianyu wrote:
> On 10/24/2016 8:19 AM, Konrad Rzeszutek Wilk wrote:
> > On Sat, Oct 22, 2016 at 07:23:03PM +0800, Lan Tianyu wrote:
> > > __serial_rx() runs in either irq handler or timer handler and non-irq
> > > keyhandler should not run in these contexts. So always force non-irq
> > > keyhandler to run in tasklet when receive a debugkey from serial port
> > 
> > If the machine is hung with an IRQ handler being stuck, and
> > one does 'Ctrl-Ax3` followed by 'C' .. which would not be invoked
> > (as it is not an IRQ handler??
> 
> If serial port's interrupt still works in this case, the 'C'
> keyhandler kexec_crash() will be invoked in a tasklet. This behavior was
> changed by my patches if includes this patch.

Right, but the tasklet won't get to run at that point - as for example
the IRQ handler is stuck - so tasklets never get run? Or maybe
they do on another CPU?


> 
> 
> > 
> > 
> > > 
> > > Signed-off-by: Lan Tianyu <tianyu.lan@intel.com>
> > > ---
> > >  xen/drivers/char/console.c | 2 +-
> > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > > 
> > > diff --git a/xen/drivers/char/console.c b/xen/drivers/char/console.c
> > > index b0f74ce..184b523 100644
> > > --- a/xen/drivers/char/console.c
> > > +++ b/xen/drivers/char/console.c
> > > @@ -347,7 +347,7 @@ static void switch_serial_input(void)
> > >  static void __serial_rx(char c, struct cpu_user_regs *regs)
> > >  {
> > >      if ( xen_rx )
> > > -        return handle_keypress(c, regs, !in_irq());
> > > +        return handle_keypress(c, regs, true);
> > > 
> > >      /* Deliver input to guest buffer, unless it is already full. */
> > >      if ( (serial_rx_prod-serial_rx_cons) != SERIAL_RX_SIZE )
> > > --
> > > 2.9.3
> > > 

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