[Xen-devel] [PATCH] xen: always handle VIRQ_TIMER first.

[Ian Campbell <ian.campbell@xxxxxxxxxx>]

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.

Signed-off-by: Ian Campbell <ian.campbell@xxxxxxxxxx>
Cc: keir@xxxxxxx
---
 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<<bit_idx)))
+                               (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);
 
-- 
1.5.6.5


_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-devel