Re: [Xen-devel] [PATCH] xen: Add comment for missing FROZEN notifier transitions

From: Julien Grall
Date: Mon Apr 04 2016 - 12:21:53 EST


(CC Stefano new e-mail address)

Hello Anna-Maria,

On 04/04/2016 13:32, Anna-Maria Gleixner wrote:
Xen guests do not offline/online CPUs during suspend/resume and
therefore FROZEN notifier transitions are not required. Add this
explanation as a comment in the code to get not confused why
CPU_TASKS_FROZEN masked transitions are not considered.

Cc: David Vrabel <david.vrabel@xxxxxxxxxx>
Cc: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>
Cc: xen-devel@xxxxxxxxxxxxxxxxxxxx
Signed-off-by: Anna-Maria Gleixner <anna-maria@xxxxxxxxxxxxx>
---
arch/arm/xen/enlighten.c | 6 ++++++
arch/x86/xen/enlighten.c | 7 +++++++
drivers/xen/events/events_fifo.c | 6 ++++++
3 files changed, 19 insertions(+)

--- a/arch/arm/xen/enlighten.c
+++ b/arch/arm/xen/enlighten.c
@@ -213,6 +213,12 @@ static int xen_cpu_notification(struct n
unsigned long action,
void *hcpu)
{
+ /*
+ * Xen guests do not offline/online CPUs during
+ * suspend/resume, thus CPU_TASKS_FROZEN masked transitions
+ * are not considered.
+ */
+
switch (action) {
case CPU_STARTING:
xen_percpu_init();
--- a/arch/x86/xen/enlighten.c
+++ b/arch/x86/xen/enlighten.c
@@ -1788,6 +1788,13 @@ static int xen_hvm_cpu_notify(struct not
void *hcpu)
{
int cpu = (long)hcpu;
+
+ /*
+ * Xen guests do not offline/online CPUs during
+ * suspend/resume, thus CPU_TASKS_FROZEN masked transitions
+ * are not considered.
+ */
+
switch (action) {
case CPU_UP_PREPARE:
xen_vcpu_setup(cpu);
--- a/drivers/xen/events/events_fifo.c
+++ b/drivers/xen/events/events_fifo.c
@@ -425,6 +425,12 @@ static int evtchn_fifo_cpu_notification(
int cpu = (long)hcpu;
int ret = 0;

+ /*
+ * Xen guests do not offline/online CPUs during
+ * suspend/resume, thus CPU_TASKS_FROZEN masked transitions
+ * are not considered.
+ */

NIT: The '*' is not aligned with the others.

+
switch (action) {
case CPU_UP_PREPARE:
if (!per_cpu(cpu_control_block, cpu))


Regards,

--
Julien Grall