From a3063dbdddea3866145a3482400edf6ad2129a83 Mon Sep 17 00:00:00 2001 From: Dexuan Cui Date: Mon, 9 Jul 2018 13:16:07 -0500 Subject: [PATCH] PCI: hv: Disable/enable IRQs rather than BH in hv_compose_msi_msg() Commit b36ec9fc8d37 ("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 88b2a09c3dab ("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 b36ec9fc8d37: 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: b36ec9fc8d37 ("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 --- drivers/pci/controller/pci-hyperv.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) diff --git a/drivers/pci/controller/pci-hyperv.c b/drivers/pci/controller/pci-hyperv.c index 6cc5036ac83cf..f6325f1a89e87 100644 --- a/drivers/pci/controller/pci-hyperv.c +++ b/drivers/pci/controller/pci-hyperv.c @@ -1073,6 +1073,7 @@ static void hv_compose_msi_msg(struct irq_data *data, struct msi_msg *msg) 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 { @@ -1164,14 +1165,15 @@ static void hv_compose_msi_msg(struct irq_data *data, struct msi_msg *msg) * 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, -- 2.39.5