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Subject[PATCH] xen/events: reset active flag for lateeoi events later
Date
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
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