[PATCH] xen: Resume PMU from non-atomic context

[PATCH] xen: Resume PMU from non-atomic context

[Boris Ostrovsky]

Resuming PMU currently triggers a warning from ___might_sleep() (assuming
CONFIG_DEBUG_ATOMIC_SLEEP is set) when xen_pmu_init() allocates GFP_KERNEL
page because we are in state resembling atomic context.

Move resuming PMU to xen_arch_resume() which is called in regular context.
For symmetry move suspending PMU to xen_arch_suspend() as well.

Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Reported-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: <stable@vger.kernel.org> # 4.3
---
 arch/x86/xen/suspend.c | 20 ++++++++++----------
 1 file changed, 10 insertions(+), 10 deletions(-)

diff --git a/arch/x86/xen/suspend.c b/arch/x86/xen/suspend.c
index feddabd..3705eab 100644
--- a/arch/x86/xen/suspend.c
+++ b/arch/x86/xen/suspend.c
@@ -68,26 +68,16 @@ static void xen_pv_post_suspend(int suspend_cancelled)
 
 void xen_arch_pre_suspend(void)
 {
-	int cpu;
-
-	for_each_online_cpu(cpu)
-		xen_pmu_finish(cpu);
-
 	if (xen_pv_domain())
 		xen_pv_pre_suspend();
 }
 
 void xen_arch_post_suspend(int cancelled)
 {
-	int cpu;
-
 	if (xen_pv_domain())
 		xen_pv_post_suspend(cancelled);
 	else
 		xen_hvm_post_suspend(cancelled);
-
-	for_each_online_cpu(cpu)
-		xen_pmu_init(cpu);
 }
 
 static void xen_vcpu_notify_restore(void *data)
@@ -106,10 +96,20 @@ static void xen_vcpu_notify_suspend(void *data)
 
 void xen_arch_resume(void)
 {
+	int cpu;
+
 	on_each_cpu(xen_vcpu_notify_restore, NULL, 1);
+
+	for_each_online_cpu(cpu)
+		xen_pmu_init(cpu);
 }
 
 void xen_arch_suspend(void)
 {
+	int cpu;
+
+	for_each_online_cpu(cpu)
+		xen_pmu_finish(cpu);
+
 	on_each_cpu(xen_vcpu_notify_suspend, NULL, 1);
 }
-- 
1.8.1.4

Re: [Xen-devel] [PATCH] xen: Resume PMU from non-atomic context

[David Vrabel]

On 02/12/15 17:10, Boris Ostrovsky wrote:
> Resuming PMU currently triggers a warning from ___might_sleep() (assuming
> CONFIG_DEBUG_ATOMIC_SLEEP is set) when xen_pmu_init() allocates GFP_KERNEL
> page because we are in state resembling atomic context.
> 
> Move resuming PMU to xen_arch_resume() which is called in regular context.
> For symmetry move suspending PMU to xen_arch_suspend() as well.

Applied to for-linus-4.4, thanks.

David