From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.linuxfoundation.org ([140.211.169.12]:56570 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2389332AbeGTNeN (ORCPT ); Fri, 20 Jul 2018 09:34:13 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Dexuan Cui , Lorenzo Pieralisi , Bjorn Helgaas , Haiyang Zhang , Stephen Hemminger , "K. Y. Srinivasan" Subject: [PATCH 4.17 067/101] PCI: hv: Disable/enable IRQs rather than BH in hv_compose_msi_msg() Date: Fri, 20 Jul 2018 14:14:13 +0200 Message-Id: <20180720121426.160586921@linuxfoundation.org> In-Reply-To: <20180720121422.837870592@linuxfoundation.org> References: <20180720121422.837870592@linuxfoundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: stable-owner@vger.kernel.org List-ID: 4.17-stable review patch. If anyone has any objections, please let me know. ------------------ From: Dexuan Cui commit 35a88a18d7ea58600e11590405bc93b08e16e7f5 upstream. Commit de0aa7b2f97d ("PCI: hv: Fix 2 hang issues in hv_compose_msi_msg()") uses local_bh_disable()/enable(), because hv_pci_onchannelcallback() can also run in tasklet context as the channel event callback, so bottom halves should be disabled to prevent a race condition. With CONFIG_PROVE_LOCKING=y in the recent mainline, or old kernels that don't have commit f71b74bca637 ("irq/softirqs: Use lockdep to assert IRQs are disabled/enabled"), when the upper layer IRQ code calls hv_compose_msi_msg() with local IRQs disabled, we'll see a warning at the beginning of __local_bh_enable_ip(): IRQs not enabled as expected WARNING: CPU: 0 PID: 408 at kernel/softirq.c:162 __local_bh_enable_ip The warning exposes an issue in de0aa7b2f97d: local_bh_enable() can potentially call do_softirq(), which is not supposed to run when local IRQs are disabled. Let's fix this by using local_irq_save()/restore() instead. Note: hv_pci_onchannelcallback() is not a hot path because it's only called when the PCI device is hot added and removed, which is infrequent. Fixes: de0aa7b2f97d ("PCI: hv: Fix 2 hang issues in hv_compose_msi_msg()") Signed-off-by: Dexuan Cui Signed-off-by: Lorenzo Pieralisi Signed-off-by: Bjorn Helgaas Reviewed-by: Haiyang Zhang Cc: stable@vger.kernel.org Cc: Stephen Hemminger Cc: K. Y. Srinivasan Signed-off-by: Greg Kroah-Hartman --- drivers/pci/host/pci-hyperv.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) --- a/drivers/pci/host/pci-hyperv.c +++ b/drivers/pci/host/pci-hyperv.c @@ -1077,6 +1077,7 @@ static void hv_compose_msi_msg(struct ir struct pci_bus *pbus; struct pci_dev *pdev; struct cpumask *dest; + unsigned long flags; struct compose_comp_ctxt comp; struct tran_int_desc *int_desc; struct { @@ -1168,14 +1169,15 @@ static void hv_compose_msi_msg(struct ir * the channel callback directly when channel->target_cpu is * the current CPU. When the higher level interrupt code * calls us with interrupt enabled, let's add the - * local_bh_disable()/enable() to avoid race. + * local_irq_save()/restore() to avoid race: + * hv_pci_onchannelcallback() can also run in tasklet. */ - local_bh_disable(); + local_irq_save(flags); if (hbus->hdev->channel->target_cpu == smp_processor_id()) hv_pci_onchannelcallback(hbus); - local_bh_enable(); + local_irq_restore(flags); if (hpdev->state == hv_pcichild_ejecting) { dev_err_once(&hbus->hdev->device,