From: Keir Fraser <keir.fraser@citrix.com>
Date: Tue, 21 Oct 2008 09:04:40 +0000 (+0100)
Subject: pv-on-hvm: Avoid rwlock livelock on save/restore.
X-Git-Tag: archive/raspbian/4.8.0-1+rpi1~1^2~14066^2~8
X-Git-Url: https://dgit.raspbian.org/%22http://www.example.com/cgi/success//%22http:/www.example.com/cgi/success/?a=commitdiff_plain;h=d24bdba9b96d862afc0a5c26d8e46a13c37bf4b7;p=xen.git

pv-on-hvm: Avoid rwlock livelock on save/restore.
Signed-off-by: Keir Fraser <keir.fraser@citrix.com>
---

diff --git a/unmodified_drivers/linux-2.6/platform-pci/machine_reboot.c b/unmodified_drivers/linux-2.6/platform-pci/machine_reboot.c
index 92b64e2589..08bf645ef7 100644
--- a/unmodified_drivers/linux-2.6/platform-pci/machine_reboot.c
+++ b/unmodified_drivers/linux-2.6/platform-pci/machine_reboot.c
@@ -11,12 +11,6 @@ struct ap_suspend_info {
 	atomic_t nr_spinning;
 };
 
-/*
- * Use a rwlock to protect the hypercall page from being executed in AP context
- * while the BSP is re-initializing it after restore.
- */
-static DEFINE_RWLOCK(suspend_lock);
-
 #ifdef CONFIG_SMP
 
 /*
@@ -33,12 +27,8 @@ static void ap_suspend(void *_info)
 	atomic_inc(&info->nr_spinning);
 	mb();
 
-	while (info->do_spin) {
+	while (info->do_spin)
 		cpu_relax();
-		read_lock(&suspend_lock);
-		HYPERVISOR_yield();
-		read_unlock(&suspend_lock);
-	}
 
 	mb();
 	atomic_dec(&info->nr_spinning);
@@ -61,9 +51,7 @@ static int bp_suspend(void)
 	suspend_cancelled = HYPERVISOR_suspend(0);
 
 	if (!suspend_cancelled) {
-		write_lock(&suspend_lock);
 		platform_pci_resume();
-		write_unlock(&suspend_lock);
 		gnttab_resume();
 		irq_resume();
 	}