linux-kernel - RE: bug seen with dynticks from CONFIG_HARDIRQS_SW

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Date:	Fri, 18 May 2007 09:49:27 +0200
From:	Thomas Gleixner <tglx@...utronix.de>
To:	"Woodruff, Richard" <r-woodruff2@...com>
Cc:	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...e.hu>
Subject: RE: bug seen with dynticks from CONFIG_HARDIRQS_SW_RESEND

On Thu, 2007-05-17 at 17:24 -0500, Woodruff, Richard wrote:
> > This is the original ARM dyntick stuff, right ?
> 
> Yes this is a version is not using clocksource.
> 
> > The dyntick support on your architecture is broken. Why does it fiddle
> > with the timer, when the system is not idle ?
> 
> I can't yet run the test sequence on the latest kernel so I'll have to
> wait to experiment.  A brief look at the new code seems to show a
> similar path but I need to actually run though it to understand better.
> 
> 
> On the irq_resend() path handle_dynamic_tick() is still called as
> before. 

No. NOHZ makes handle_dynamic_tick() a NOP. handle_dynamic_tick()
depends on CONFIG_NO_IDLE_HZ, which is not used when NOHZ is active.

The problem could only arise, when something would disable/enable the
timer interrupt.

	tglx


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