linux-kernel - [PATCH 2/4] Drivers: hv: vmbus: avoid wait_for

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Message-Id: <1455291770-15672-3-git-send-email-vkuznets@redhat.com>
Date:	Fri, 12 Feb 2016 16:42:48 +0100
From:	Vitaly Kuznetsov <vkuznets@...hat.com>
To:	devel@...uxdriverproject.org
Cc:	linux-kernel@...r.kernel.org,
	"K. Y. Srinivasan" <kys@...rosoft.com>,
	Haiyang Zhang <haiyangz@...rosoft.com>,
	Radim Krcmar <rkrcmar@...hat.com>,
	Cathy Avery <cavery@...hat.com>
Subject: [PATCH 2/4] Drivers: hv: vmbus: avoid wait_for_completion() on crash

wait_for_completion() may sleep, it enables interrupts and this
is something we really want to avoid on crashes because interrupt
handlers can cause other crashes. Switch to the recently introduced
vmbus_wait_for_unload() doing busy wait instead.

Reported-by: Radim Krcmar <rkrcmar@...hat.com>
Signed-off-by: Vitaly Kuznetsov <vkuznets@...hat.com>
---
 drivers/hv/channel_mgmt.c | 4 ++--
 drivers/hv/connection.c   | 2 +-
 drivers/hv/hyperv_vmbus.h | 2 +-
 drivers/hv/vmbus_drv.c    | 4 ++--
 4 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/drivers/hv/channel_mgmt.c b/drivers/hv/channel_mgmt.c
index 763d0c1..bd60207 100644
--- a/drivers/hv/channel_mgmt.c
+++ b/drivers/hv/channel_mgmt.c
@@ -556,7 +556,7 @@ static void vmbus_unload_response(struct vmbus_channel_message_header *hdr)
 	complete(&vmbus_connection.unload_event);
 }
 
-void vmbus_initiate_unload(void)
+void vmbus_initiate_unload(bool crash)
 {
 	struct vmbus_channel_message_header hdr;
 
@@ -573,7 +573,7 @@ void vmbus_initiate_unload(void)
 	 * vmbus_initiate_unload() is also called on crash and the crash can be
 	 * happening in an interrupt context, where scheduling is impossible.
 	 */
-	if (!in_interrupt())
+	if (!crash)
 		wait_for_completion(&vmbus_connection.unload_event);
 	else
 		vmbus_wait_for_unload();
diff --git a/drivers/hv/connection.c b/drivers/hv/connection.c
index 3dc5a9c..fb63d30 100644
--- a/drivers/hv/connection.c
+++ b/drivers/hv/connection.c
@@ -236,7 +236,7 @@ void vmbus_disconnect(void)
 	/*
 	 * First send the unload request to the host.
 	 */
-	vmbus_initiate_unload();
+	vmbus_initiate_unload(false);
 
 	if (vmbus_connection.work_queue) {
 		drain_workqueue(vmbus_connection.work_queue);
diff --git a/drivers/hv/hyperv_vmbus.h b/drivers/hv/hyperv_vmbus.h
index 4ebc796..e6160a0 100644
--- a/drivers/hv/hyperv_vmbus.h
+++ b/drivers/hv/hyperv_vmbus.h
@@ -665,7 +665,7 @@ void hv_vss_onchannelcallback(void *);
 int hv_fcopy_init(struct hv_util_service *);
 void hv_fcopy_deinit(void);
 void hv_fcopy_onchannelcallback(void *);
-void vmbus_initiate_unload(void);
+void vmbus_initiate_unload(bool crash);
 
 static inline void hv_poll_channel(struct vmbus_channel *channel,
 				   void (*cb)(void *))
diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c
index 895eeed..08f98a1 100644
--- a/drivers/hv/vmbus_drv.c
+++ b/drivers/hv/vmbus_drv.c
@@ -1266,7 +1266,7 @@ static void hv_kexec_handler(void)
 	int cpu;
 
 	hv_synic_clockevents_cleanup();
-	vmbus_initiate_unload();
+	vmbus_initiate_unload(false);
 	for_each_online_cpu(cpu)
 		smp_call_function_single(cpu, hv_synic_cleanup, NULL, 1);
 	hv_cleanup();
@@ -1274,7 +1274,7 @@ static void hv_kexec_handler(void)
 
 static void hv_crash_handler(struct pt_regs *regs)
 {
-	vmbus_initiate_unload();
+	vmbus_initiate_unload(true);
 	/*
 	 * In crash handler we can't schedule synic cleanup for all CPUs,
 	 * doing the cleanup for current CPU only. This should be sufficient
-- 
2.5.0