From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jeremy Fitzhardinge Subject: Re: [PATCH] xen: always handle VIRQ_TIMER first. Date: Fri, 15 Oct 2010 10:18:07 -0700 Message-ID: <4CB88CCF.3040305@goop.org> References: <1287139966-19391-1-git-send-email-ian.campbell@citrix.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-15 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1287139966-19391-1-git-send-email-ian.campbell@citrix.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xensource.com Errors-To: xen-devel-bounces@lists.xensource.com To: Ian Campbell Cc: xen-devel@lists.xensource.com, keir@xen.org List-Id: xen-devel@lists.xenproject.org On 10/15/2010 03:52 AM, Ian Campbell wrote: > This ensures that system is updated before calling any hard irq > handlers after a long period of ticklessness. If we do not do this > then hardirq will see a jiffies from before the period of ticklessness > and make intcorrect decisions regarding timer expiry etc. > > This resolves issues e.g. with USB keyboard timer repeats. > > Based on a patch by Keir Fraser. I talked about this with James, and it makes no sense to me at all. J > Signed-off-by: Ian Campbell > Cc: keir@xen.org > --- > drivers/xen/events.c | 22 +++++++++++++++++++++- > 1 files changed, 21 insertions(+), 1 deletions(-) > > diff --git a/drivers/xen/events.c b/drivers/xen/events.c > index c9d1d4a..1496ba5 100644 > --- a/drivers/xen/events.c > +++ b/drivers/xen/events.c > @@ -1052,6 +1052,7 @@ static void __xen_evtchn_do_upcall(struct pt_regs *regs) > > do { > unsigned long pending_words; > + int irq; > > vcpu_info->evtchn_upcall_pending = 0; > > @@ -1062,6 +1063,24 @@ static void __xen_evtchn_do_upcall(struct pt_regs *regs) > /* Clear master flag /before/ clearing selector flag. */ > wmb(); > #endif > + > + /* > + * Handle timer interrupts before all others, so that all > + * hardirq handlers see an up-to-date system time even if we > + * have just woken from a long idle period. > + */ > + irq = percpu_read(virq_to_irq[VIRQ_TIMER]); > + if (irq != -1) { > + int word_idx; > + int bit_idx; > + int port = evtchn_from_irq(irq); > + word_idx = port / BITS_PER_LONG; > + bit_idx = port % BITS_PER_LONG; > + if (VALID_EVTCHN(port) && > + (active_evtchns(cpu, s, word_idx) & (1UL< + (void)handle_irq(irq, regs); > + } > + > pending_words = xchg(&vcpu_info->evtchn_pending_sel, 0); > while (pending_words != 0) { > unsigned long pending_bits; > @@ -1071,9 +1090,10 @@ static void __xen_evtchn_do_upcall(struct pt_regs *regs) > while ((pending_bits = active_evtchns(cpu, s, word_idx)) != 0) { > int bit_idx = __ffs(pending_bits); > int port = (word_idx * BITS_PER_LONG) + bit_idx; > - int irq = evtchn_to_irq[port]; > struct irq_desc *desc; > > + irq = evtchn_to_irq[port]; > + > mask_evtchn(port); > clear_evtchn(port); >