* [PATCH] xen/events: reset active flag for lateeoi events later
@ 2021-06-23 13:09 Juergen Gross
2021-06-23 23:18 ` Boris Ostrovsky
2021-07-05 9:00 ` Ross Lagerwall
0 siblings, 2 replies; 4+ messages in thread
From: Juergen Gross @ 2021-06-23 13:09 UTC (permalink / raw)
To: xen-devel, linux-kernel
Cc: Juergen Gross, Boris Ostrovsky, Stefano Stabellini, Julien Grall
In order to avoid a race condition for user events when changing
cpu affinity reset the active flag only when EOI-ing the event.
This is working fine as all user events are lateeoi events. Note that
lateeoi_ack_mask_dynirq() is not modified as there is no explicit call
to xen_irq_lateeoi() expected later.
Reported-by: Julien Grall <julien@xen.org>
Fixes: b6622798bc50b62 ("xen/events: avoid handling the same event on two cpus at the same time")
Tested-by: Julien Grall <julien@xen.org>
Signed-off-by: Juergen Gross <jgross@suse.com>
---
drivers/xen/events/events_base.c | 11 ++++++++++-
1 file changed, 10 insertions(+), 1 deletion(-)
diff --git a/drivers/xen/events/events_base.c b/drivers/xen/events/events_base.c
index 7bbfd58958bc..d7e361fb0548 100644
--- a/drivers/xen/events/events_base.c
+++ b/drivers/xen/events/events_base.c
@@ -642,6 +642,9 @@ static void xen_irq_lateeoi_locked(struct irq_info *info, bool spurious)
}
info->eoi_time = 0;
+
+ /* is_active hasn't been reset yet, do it now. */
+ smp_store_release(&info->is_active, 0);
do_unmask(info, EVT_MASK_REASON_EOI_PENDING);
}
@@ -811,6 +814,7 @@ static void xen_evtchn_close(evtchn_port_t port)
BUG();
}
+/* Not called for lateeoi events. */
static void event_handler_exit(struct irq_info *info)
{
smp_store_release(&info->is_active, 0);
@@ -1883,7 +1887,12 @@ static void lateeoi_ack_dynirq(struct irq_data *data)
if (VALID_EVTCHN(evtchn)) {
do_mask(info, EVT_MASK_REASON_EOI_PENDING);
- event_handler_exit(info);
+ /*
+ * Don't call event_handler_exit().
+ * Need to keep is_active non-zero in order to ignore re-raised
+ * events after cpu affinity changes while a lateeoi is pending.
+ */
+ clear_evtchn(evtchn);
}
}
--
2.26.2
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH] xen/events: reset active flag for lateeoi events later
2021-06-23 13:09 [PATCH] xen/events: reset active flag for lateeoi events later Juergen Gross
@ 2021-06-23 23:18 ` Boris Ostrovsky
2021-07-05 9:00 ` Ross Lagerwall
1 sibling, 0 replies; 4+ messages in thread
From: Boris Ostrovsky @ 2021-06-23 23:18 UTC (permalink / raw)
To: Juergen Gross, xen-devel, linux-kernel; +Cc: Stefano Stabellini, Julien Grall
On 6/23/21 9:09 AM, Juergen Gross wrote:
> In order to avoid a race condition for user events when changing
> cpu affinity reset the active flag only when EOI-ing the event.
>
> This is working fine as all user events are lateeoi events. Note that
> lateeoi_ack_mask_dynirq() is not modified as there is no explicit call
> to xen_irq_lateeoi() expected later.
>
> Reported-by: Julien Grall <julien@xen.org>
> Fixes: b6622798bc50b62 ("xen/events: avoid handling the same event on two cpus at the same time")
> Tested-by: Julien Grall <julien@xen.org>
> Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Boris Ostrovsky <boris.ostrvsky@oracle.com>
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] xen/events: reset active flag for lateeoi events later
2021-06-23 13:09 [PATCH] xen/events: reset active flag for lateeoi events later Juergen Gross
2021-06-23 23:18 ` Boris Ostrovsky
@ 2021-07-05 9:00 ` Ross Lagerwall
2021-07-05 9:16 ` Juergen Gross
1 sibling, 1 reply; 4+ messages in thread
From: Ross Lagerwall @ 2021-07-05 9:00 UTC (permalink / raw)
To: Juergen Gross, xen-devel, linux-kernel
Cc: Boris Ostrovsky, Stefano Stabellini, Julien Grall
On 2021-06-23 14:09, Juergen Gross wrote:
> In order to avoid a race condition for user events when changing
> cpu affinity reset the active flag only when EOI-ing the event.
>
> This is working fine as all user events are lateeoi events. Note that
> lateeoi_ack_mask_dynirq() is not modified as there is no explicit call
> to xen_irq_lateeoi() expected later.
>
> Reported-by: Julien Grall <julien@xen.org>
> Fixes: b6622798bc50b62 ("xen/events: avoid handling the same event on two cpus at the same time")
> Tested-by: Julien Grall <julien@xen.org>
> Signed-off-by: Juergen Gross <jgross@suse.com>
> ---
Hi Juergen,
Are you planning on backporting this fix to releases <= 5.10?
I think the fix may need some minor adjustment to make it work after
"xen/events: fix setting irq affinity" since both lateeoi_ack_dynirq()
and lateeoi_mask_ack_dynirq() were adjusted to call ack_dynirq().
Thanks,
Ross
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] xen/events: reset active flag for lateeoi events later
2021-07-05 9:00 ` Ross Lagerwall
@ 2021-07-05 9:16 ` Juergen Gross
0 siblings, 0 replies; 4+ messages in thread
From: Juergen Gross @ 2021-07-05 9:16 UTC (permalink / raw)
To: Ross Lagerwall, xen-devel, linux-kernel
Cc: Boris Ostrovsky, Stefano Stabellini, Julien Grall
[-- Attachment #1.1.1: Type: text/plain, Size: 806 bytes --]
On 05.07.21 11:00, Ross Lagerwall wrote:
> On 2021-06-23 14:09, Juergen Gross wrote:
>> In order to avoid a race condition for user events when changing
>> cpu affinity reset the active flag only when EOI-ing the event.
>>
>> This is working fine as all user events are lateeoi events. Note that
>> lateeoi_ack_mask_dynirq() is not modified as there is no explicit call
>> to xen_irq_lateeoi() expected later.
>>
>> Reported-by: Julien Grall <julien@xen.org>
>> Fixes: b6622798bc50b62 ("xen/events: avoid handling the same event on two cpus at the same time")
>> Tested-by: Julien Grall <julien@xen.org>
>> Signed-off-by: Juergen Gross <jgross@suse.com>
>> ---
>
> Hi Juergen,
>
> Are you planning on backporting this fix to releases <= 5.10?
It is on my todo list. :-)
Juergen
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^ permalink raw reply [flat|nested] 4+ messages in thread
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2021-06-23 13:09 [PATCH] xen/events: reset active flag for lateeoi events later Juergen Gross
2021-06-23 23:18 ` Boris Ostrovsky
2021-07-05 9:00 ` Ross Lagerwall
2021-07-05 9:16 ` Juergen Gross
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