Patchwork [3.8.y.z,extended,stable] Patch "xen/events: Handle VIRQ_TIMER before any other hardirq in event loop." has been added to staging queue

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Submitter Kamal Mostafa
Date June 25, 2013, 10:19 p.m.
Message ID <1372198799-17872-1-git-send-email-kamal@canonical.com>
Download mbox | patch
Permalink /patch/254519/
State New
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Comments

Kamal Mostafa - June 25, 2013, 10:19 p.m.
This is a note to let you know that I have just added a patch titled

    xen/events: Handle VIRQ_TIMER before any other hardirq in event loop.

to the linux-3.8.y-queue branch of the 3.8.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.8.y-queue

This patch is scheduled to be released in version 3.8.13.4.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.8.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

------

From 3ab56a2ad53d95cd504668a6d7749a4273791cfc Mon Sep 17 00:00:00 2001
From: Keir Fraser <keir.fraser@citrix.com>
Date: Thu, 28 Mar 2013 10:03:36 -0400
Subject: xen/events: Handle VIRQ_TIMER before any other hardirq in event loop.

commit bee980d9e9642e96351fa3ca9077b853ecf62f57 upstream.

This avoids any other hardirq handler seeing a very stale jiffies
value immediately after wakeup from a long idle period. The one
observable symptom of this was a USB keyboard, with software keyboard
repeat, which would always repeat a key immediately that it was
pressed. This is due to the key press waking the guest, the key
handler immediately runs, sees an old jiffies value, and then that
jiffies value significantly updated, before the key is unpressed.

Reviewed-by: David Vrabel <david.vrabel@citrix.com>
Signed-off-by: Keir Fraser <keir.fraser@citrix.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
[ luis: backported to 3.5:
  - replaced xen_ulong_t by unsigned long ]
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
---
 drivers/xen/events.c | 19 +++++++++++++++----
 1 file changed, 15 insertions(+), 4 deletions(-)

--
1.8.1.2

Patch

diff --git a/drivers/xen/events.c b/drivers/xen/events.c
index 8aa3867..7ae3821 100644
--- a/drivers/xen/events.c
+++ b/drivers/xen/events.c
@@ -1298,7 +1298,7 @@  static void __xen_evtchn_do_upcall(void)
 {
 	int start_word_idx, start_bit_idx;
 	int word_idx, bit_idx;
-	int i;
+	int i, irq;
 	int cpu = get_cpu();
 	struct shared_info *s = HYPERVISOR_shared_info;
 	struct vcpu_info *vcpu_info = __this_cpu_read(xen_vcpu);
@@ -1306,6 +1306,8 @@  static void __xen_evtchn_do_upcall(void)

 	do {
 		unsigned long pending_words;
+		unsigned long pending_bits;
+		struct irq_desc *desc;

 		vcpu_info->evtchn_upcall_pending = 0;

@@ -1316,6 +1318,17 @@  static void __xen_evtchn_do_upcall(void)
 		/* Clear master flag /before/ clearing selector flag. */
 		wmb();
 #endif
+		if ((irq = per_cpu(virq_to_irq, cpu)[VIRQ_TIMER]) != -1) {
+			int evtchn = evtchn_from_irq(irq);
+			word_idx = evtchn / BITS_PER_LONG;
+			pending_bits = evtchn % BITS_PER_LONG;
+			if (active_evtchns(cpu, s, word_idx) & (1ULL << pending_bits)) {
+				desc = irq_to_desc(irq);
+				if (desc)
+					generic_handle_irq_desc(irq, desc);
+			}
+		}
+
 		pending_words = xchg(&vcpu_info->evtchn_pending_sel, 0);

 		start_word_idx = __this_cpu_read(current_word_idx);
@@ -1324,7 +1337,6 @@  static void __xen_evtchn_do_upcall(void)
 		word_idx = start_word_idx;

 		for (i = 0; pending_words != 0; i++) {
-			unsigned long pending_bits;
 			unsigned long words;

 			words = MASK_LSBS(pending_words, word_idx);
@@ -1353,8 +1365,7 @@  static void __xen_evtchn_do_upcall(void)

 			do {
 				unsigned long bits;
-				int port, irq;
-				struct irq_desc *desc;
+				int port;

 				bits = MASK_LSBS(pending_bits, bit_idx);