From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.linuxfoundation.org ([140.211.169.12]:34946 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750888AbcIINnL (ORCPT ); Fri, 9 Sep 2016 09:43:11 -0400 Subject: Patch "[PATCH 098/135] Drivers: hv: vmbus: avoid scheduling in interrupt" has been added to the 4.4-stable tree To: vkuznets@redhat.com, alexander.levin@verizon.com, gregkh@linuxfoundation.org, kys@microsoft.com Cc: , From: Date: Fri, 09 Sep 2016 15:38:30 +0200 Message-ID: <147342831076164@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org List-ID: This is a note to let you know that I've just added the patch titled [PATCH 098/135] Drivers: hv: vmbus: avoid scheduling in interrupt to the 4.4-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: 0098-Drivers-hv-vmbus-avoid-scheduling-in-interrupt-conte.patch and it can be found in the queue-4.4 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let know about it. >>From 04023b914cfb9c54dc70f1407086536218145729 Mon Sep 17 00:00:00 2001 From: Vitaly Kuznetsov Date: Wed, 27 Jan 2016 22:29:35 -0800 Subject: [PATCH 098/135] Drivers: hv: vmbus: avoid scheduling in interrupt context in vmbus_initiate_unload() [ Upstream commit 415719160de3fae3bb9cbc617664649919cd00d0 ] We have to call vmbus_initiate_unload() on crash to make kdump work but the crash can also be happening in interrupt (e.g. Sysrq + c results in such) where we can't schedule or the following will happen: [ 314.905786] bad: scheduling from the idle thread! Just skipping the wait (and even adding some random wait here) won't help: to make host-side magic working we're supposed to receive CHANNELMSG_UNLOAD (and actually confirm the fact that we received it) but we can't use interrupt-base path (vmbus_isr()-> vmbus_on_msg_dpc()). Implement a simple busy wait ignoring all the other messages and use it if we're in an interrupt context. Signed-off-by: Vitaly Kuznetsov Signed-off-by: K. Y. Srinivasan Signed-off-by: Greg Kroah-Hartman Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman --- drivers/hv/channel_mgmt.c | 44 +++++++++++++++++++++++++++++++++++++++++++- 1 file changed, 43 insertions(+), 1 deletion(-) --- a/drivers/hv/channel_mgmt.c +++ b/drivers/hv/channel_mgmt.c @@ -28,6 +28,7 @@ #include #include #include +#include #include #include "hyperv_vmbus.h" @@ -499,6 +500,40 @@ static void init_vp_index(struct vmbus_c channel->target_vp = hv_context.vp_index[cur_cpu]; } +static void vmbus_wait_for_unload(void) +{ + int cpu = smp_processor_id(); + void *page_addr = hv_context.synic_message_page[cpu]; + struct hv_message *msg = (struct hv_message *)page_addr + + VMBUS_MESSAGE_SINT; + struct vmbus_channel_message_header *hdr; + bool unloaded = false; + + while (1) { + if (msg->header.message_type == HVMSG_NONE) { + mdelay(10); + continue; + } + + hdr = (struct vmbus_channel_message_header *)msg->u.payload; + if (hdr->msgtype == CHANNELMSG_UNLOAD_RESPONSE) + unloaded = true; + + msg->header.message_type = HVMSG_NONE; + /* + * header.message_type needs to be written before we do + * wrmsrl() below. + */ + mb(); + + if (msg->header.message_flags.msg_pending) + wrmsrl(HV_X64_MSR_EOM, 0); + + if (unloaded) + break; + } +} + /* * vmbus_unload_response - Handler for the unload response. */ @@ -524,7 +559,14 @@ void vmbus_initiate_unload(void) hdr.msgtype = CHANNELMSG_UNLOAD; vmbus_post_msg(&hdr, sizeof(struct vmbus_channel_message_header)); - wait_for_completion(&vmbus_connection.unload_event); + /* + * 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()) + wait_for_completion(&vmbus_connection.unload_event); + else + vmbus_wait_for_unload(); } /* Patches currently in stable-queue which might be from vkuznets@redhat.com are queue-4.4/0038-drivers-hv-cleanup-synic-msrs-if-vmbus-connect-faile.patch queue-4.4/0097-Drivers-hv-vmbus-avoid-infinite-loop-in-init_vp_inde.patch queue-4.4/0118-clocksource-Allow-unregistering-the-watchdog.patch queue-4.4/0099-Drivers-hv-vmbus-don-t-manipulate-with-clocksources-.patch queue-4.4/0127-x86-hyperv-Avoid-reporting-bogus-NMI-status-for-Gen2.patch queue-4.4/0098-Drivers-hv-vmbus-avoid-scheduling-in-interrupt-conte.patch