From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-18.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 6E1F9C433E0 for ; Tue, 2 Feb 2021 18:44:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3DE6D64E34 for ; Tue, 2 Feb 2021 18:44:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238895AbhBBSoI (ORCPT ); Tue, 2 Feb 2021 13:44:08 -0500 Received: from mail.kernel.org ([198.145.29.99]:46314 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233717AbhBBOCv (ORCPT ); Tue, 2 Feb 2021 09:02:51 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id 8A5FA6500C; Tue, 2 Feb 2021 13:48:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1612273686; bh=TpZbbwr9wlvVCQwnktn8RnArixjRDNYTuiSMPBhjGlQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=W1hufQ0JW6bMyoxeyN0G0+pcSwRay0aB5jvSe8MUzgYE5vtb4uwakTg6cVBHI7WRk xNhDTN1QHTvoH47nDuMKonL4Fky8GvXI/PUkwR3Q0ieYoMmnqI7sSZ6tF1YAsjv+MV TIeKThsDHfsWvrUnjs46QRenDzgwSQ0aQVLEo22g= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Juergen Gross , David Woodhouse , Salvatore Bonaccorso , Jason Andryuk Subject: [PATCH 5.4 22/61] xen: Fix XenStore initialisation for XS_LOCAL Date: Tue, 2 Feb 2021 14:38:00 +0100 Message-Id: <20210202132947.395417514@linuxfoundation.org> X-Mailer: git-send-email 2.30.0 In-Reply-To: <20210202132946.480479453@linuxfoundation.org> References: <20210202132946.480479453@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: David Woodhouse commit 5f46400f7a6a4fad635d5a79e2aa5a04a30ffea1 upstream. In commit 3499ba8198ca ("xen: Fix event channel callback via INTX/GSI") I reworked the triggering of xenbus_probe(). I tried to simplify things by taking out the workqueue based startup triggered from wake_waiting(); the somewhat poorly named xenbus IRQ handler. I missed the fact that in the XS_LOCAL case (Dom0 starting its own xenstored or xenstore-stubdom, which happens after the kernel is booted completely), that IRQ-based trigger is still actually needed. So... put it back, except more cleanly. By just spawning a xenbus_probe thread which waits on xb_waitq and runs the probe the first time it gets woken, just as the workqueue-based hack did. This is actually a nicer approach for *all* the back ends with different interrupt methods, and we can switch them all over to that without the complex conditions for when to trigger it. But not in -rc6. This is the minimal fix for the regression, although it's a step in the right direction instead of doing a partial revert and actually putting the workqueue back. It's also simpler than the workqueue. Fixes: 3499ba8198ca ("xen: Fix event channel callback via INTX/GSI") Reported-by: Juergen Gross Signed-off-by: David Woodhouse Reviewed-by: Juergen Gross Link: https://lore.kernel.org/r/4c9af052a6e0f6485d1de43f2c38b1461996db99.camel@infradead.org Signed-off-by: Juergen Gross Cc: Salvatore Bonaccorso Cc: Jason Andryuk Signed-off-by: Greg Kroah-Hartman --- drivers/xen/xenbus/xenbus_probe.c | 31 +++++++++++++++++++++++++++++++ 1 file changed, 31 insertions(+) --- a/drivers/xen/xenbus/xenbus_probe.c +++ b/drivers/xen/xenbus/xenbus_probe.c @@ -714,6 +714,23 @@ static bool xs_hvm_defer_init_for_callba #endif } +static int xenbus_probe_thread(void *unused) +{ + DEFINE_WAIT(w); + + /* + * We actually just want to wait for *any* trigger of xb_waitq, + * and run xenbus_probe() the moment it occurs. + */ + prepare_to_wait(&xb_waitq, &w, TASK_INTERRUPTIBLE); + schedule(); + finish_wait(&xb_waitq, &w); + + DPRINTK("probing"); + xenbus_probe(); + return 0; +} + static int __init xenbus_probe_initcall(void) { /* @@ -725,6 +742,20 @@ static int __init xenbus_probe_initcall( !xs_hvm_defer_init_for_callback())) xenbus_probe(); + /* + * For XS_LOCAL, spawn a thread which will wait for xenstored + * or a xenstore-stubdom to be started, then probe. It will be + * triggered when communication starts happening, by waiting + * on xb_waitq. + */ + if (xen_store_domain_type == XS_LOCAL) { + struct task_struct *probe_task; + + probe_task = kthread_run(xenbus_probe_thread, NULL, + "xenbus_probe"); + if (IS_ERR(probe_task)) + return PTR_ERR(probe_task); + } return 0; } device_initcall(xenbus_probe_initcall);