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=-6.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, 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 1CA6AC2BB85 for ; Thu, 16 Apr 2020 15:16:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id F0732214D8 for ; Thu, 16 Apr 2020 15:16:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1587050198; bh=3ScBCzDGVqDqZeQ7247CTqy5NBsjjC2WXKUdOEqo8bM=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=OlLle2D1BDcv8/eEGw+P3qt3aPd20e7wjyezTg7kl6SHC/O4/tKlukG2T04groaZs 48F4A0VD6oa/j1rxrcXXwzQwwqaX6mpTxusnmEr8M/kR0qFSekuM+DBAW9NNc5dZG2 FcCfzsK20Wzg21sPs/WRK3BiE7fCKS+JELAEotKQ= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729381AbgDPNuB (ORCPT ); Thu, 16 Apr 2020 09:50:01 -0400 Received: from mail.kernel.org ([198.145.29.99]:48578 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2897328AbgDPNg0 (ORCPT ); Thu, 16 Apr 2020 09:36:26 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 0041A208E4; Thu, 16 Apr 2020 13:36:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1587044185; bh=3ScBCzDGVqDqZeQ7247CTqy5NBsjjC2WXKUdOEqo8bM=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=GkP4ISPjtOc5QS1734EDSdymCN0AK5USmXH1zzd8xZOA/zgE30NcNWZt/HtSBKVpv AM+ymR8HTOz7z3lPhpHtWgxkxBe6e1CAICCTZ+yrgYeZZ4/3DjPouuGRCCwlXDm/yg EAZCUIPxBqSnWxd4dooUS+UiP+uJz8bHkS9+nXu8= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, David Hoyer , Lukas Wunner , Bjorn Helgaas , Keith Busch Subject: [PATCH 5.5 113/257] PCI: pciehp: Fix indefinite wait on sysfs requests Date: Thu, 16 Apr 2020 15:22:44 +0200 Message-Id: <20200416131340.380324440@linuxfoundation.org> X-Mailer: git-send-email 2.26.1 In-Reply-To: <20200416131325.891903893@linuxfoundation.org> References: <20200416131325.891903893@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Lukas Wunner commit 3e487d2e4aa466decd226353755c9d423e8fbacc upstream. David Hoyer reports that powering pciehp slots up or down via sysfs may hang: The call to wait_event() in pciehp_sysfs_enable_slot() and _disable_slot() does not return because ctrl->ist_running remains true. This flag, which was introduced by commit 157c1062fcd8 ("PCI: pciehp: Avoid returning prematurely from sysfs requests"), signifies that the IRQ thread pciehp_ist() is running. It is set to true at the top of pciehp_ist() and reset to false at the end. However there are two additional return statements in pciehp_ist() before which the commit neglected to reset the flag to false and wake up waiters for the flag. That omission opens up the following race when powering up the slot: * pciehp_ist() runs because a PCI_EXP_SLTSTA_PDC event was requested by pciehp_sysfs_enable_slot() * pciehp_ist() turns on slot power via the following call stack: pciehp_handle_presence_or_link_change() -> pciehp_enable_slot() -> __pciehp_enable_slot() -> board_added() -> pciehp_power_on_slot() * after slot power is turned on, the link comes up, resulting in a PCI_EXP_SLTSTA_DLLSC event * the IRQ handler pciehp_isr() stores the event in ctrl->pending_events and returns IRQ_WAKE_THREAD * the IRQ thread is already woken (it's bringing up the slot), but the genirq code remembers to re-run the IRQ thread after it has finished (such that it can deal with the new event) by setting IRQTF_RUNTHREAD via __handle_irq_event_percpu() -> __irq_wake_thread() * the IRQ thread removes PCI_EXP_SLTSTA_DLLSC from ctrl->pending_events via board_added() -> pciehp_check_link_status() in order to deal with presence and link flaps per commit 6c35a1ac3da6 ("PCI: pciehp: Tolerate initially unstable link") * after pciehp_ist() has successfully brought up the slot, it resets ctrl->ist_running to false and wakes up the sysfs requester * the genirq code re-runs pciehp_ist(), which sets ctrl->ist_running to true but then returns with IRQ_NONE because ctrl->pending_events is empty * pciehp_sysfs_enable_slot() is finally woken but notices that ctrl->ist_running is true, hence continues waiting The only way to get the hung task going again is to trigger a hotplug event which brings down the slot, e.g. by yanking out the card. The same race exists when powering down the slot because remove_board() likewise clears link or presence changes in ctrl->pending_events per commit 3943af9d01e9 ("PCI: pciehp: Ignore Link State Changes after powering off a slot") and thereby may cause a re-run of pciehp_ist() which returns with IRQ_NONE without resetting ctrl->ist_running to false. Fix by adding a goto label before the teardown steps at the end of pciehp_ist() and jumping to that label from the two return statements which currently neglect to reset the ctrl->ist_running flag. Fixes: 157c1062fcd8 ("PCI: pciehp: Avoid returning prematurely from sysfs requests") Link: https://lore.kernel.org/r/cca1effa488065cb055120aa01b65719094bdcb5.1584530321.git.lukas@wunner.de Reported-by: David Hoyer Signed-off-by: Lukas Wunner Signed-off-by: Bjorn Helgaas Reviewed-by: Keith Busch Cc: stable@vger.kernel.org # v4.19+ Signed-off-by: Greg Kroah-Hartman --- drivers/pci/hotplug/pciehp_hpc.c | 14 +++++++------- 1 file changed, 7 insertions(+), 7 deletions(-) --- a/drivers/pci/hotplug/pciehp_hpc.c +++ b/drivers/pci/hotplug/pciehp_hpc.c @@ -625,17 +625,15 @@ static irqreturn_t pciehp_ist(int irq, v if (atomic_fetch_and(~RERUN_ISR, &ctrl->pending_events) & RERUN_ISR) { ret = pciehp_isr(irq, dev_id); enable_irq(irq); - if (ret != IRQ_WAKE_THREAD) { - pci_config_pm_runtime_put(pdev); - return ret; - } + if (ret != IRQ_WAKE_THREAD) + goto out; } synchronize_hardirq(irq); events = atomic_xchg(&ctrl->pending_events, 0); if (!events) { - pci_config_pm_runtime_put(pdev); - return IRQ_NONE; + ret = IRQ_NONE; + goto out; } /* Check Attention Button Pressed */ @@ -664,10 +662,12 @@ static irqreturn_t pciehp_ist(int irq, v pciehp_handle_presence_or_link_change(ctrl, events); up_read(&ctrl->reset_lock); + ret = IRQ_HANDLED; +out: pci_config_pm_runtime_put(pdev); ctrl->ist_running = false; wake_up(&ctrl->requester); - return IRQ_HANDLED; + return ret; } static int pciehp_poll(void *data)