From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Vrabel Subject: Re: [PATCH] xen/events/fifo: Consume unprocessed events when a CPU dies Date: Fri, 19 Jun 2015 17:06:17 +0100 Message-ID: <55843DF9.5090704@citrix.com> References: <1434726957-929-1-git-send-email-ross.lagerwall@citrix.com> <55843D1C.9070905@oracle.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from mail6.bemta3.messagelabs.com ([195.245.230.39]) by lists.xen.org with esmtp (Exim 4.72) (envelope-from ) id 1Z5yoE-0007FD-2t for xen-devel@lists.xenproject.org; Fri, 19 Jun 2015 16:06:26 +0000 In-Reply-To: <55843D1C.9070905@oracle.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Boris Ostrovsky , Ross Lagerwall , xen-devel@lists.xenproject.org List-Id: xen-devel@lists.xenproject.org On 19/06/15 17:02, Boris Ostrovsky wrote: > On 06/19/2015 11:15 AM, Ross Lagerwall wrote: >> When a CPU is offlined, there may be unprocessed events on a port for >> that CPU. If the port is subsequently reused on a different CPU, it >> could be in an unexpected state with the link bit set, resulting in >> interrupts being missed. Fix this by consuming any unprocessed events >> for a particular CPU when that CPU dies. >> >> Signed-off-by: Ross Lagerwall >> --- >> drivers/xen/events/events_fifo.c | 23 ++++++++++++++++++----- >> 1 file changed, 18 insertions(+), 5 deletions(-) >> >> diff --git a/drivers/xen/events/events_fifo.c >> b/drivers/xen/events/events_fifo.c >> index 417415d..1dd0ba12 100644 >> --- a/drivers/xen/events/events_fifo.c >> +++ b/drivers/xen/events/events_fifo.c >> @@ -281,7 +281,8 @@ static void handle_irq_for_port(unsigned port) >> static void consume_one_event(unsigned cpu, >> struct evtchn_fifo_control_block *control_block, >> - unsigned priority, unsigned long *ready) >> + unsigned priority, unsigned long *ready, >> + bool drop) >> { >> struct evtchn_fifo_queue *q = &per_cpu(cpu_queue, cpu); >> uint32_t head; >> @@ -313,13 +314,17 @@ static void consume_one_event(unsigned cpu, >> if (head == 0) >> clear_bit(priority, ready); >> - if (evtchn_fifo_is_pending(port) && !evtchn_fifo_is_masked(port)) >> - handle_irq_for_port(port); >> + if (evtchn_fifo_is_pending(port) && !evtchn_fifo_is_masked(port)) { >> + if (unlikely(drop)) >> + pr_warn("Dropping pending event for port %u\n", port); > > Maybe pr_info (or pr_notice)? We want a warning here because we think this shouldn't happen -- if it does we actually need to retrigger the event on its new CPU. > Also, why not do this (testing for unprocessed events) in > xen_evtchn_close()? We can't do anything about them when closing because they may be in the middle of a queue. David