4.14-stable review patch. If anyone has any objections, please let me know.
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From: Dexuan Cui decui@microsoft.com
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 decui@microsoft.com Signed-off-by: Lorenzo Pieralisi lorenzo.pieralisi@arm.com Signed-off-by: Bjorn Helgaas bhelgaas@google.com Reviewed-by: Haiyang Zhang haiyangz@microsoft.com Cc: stable@vger.kernel.org Cc: Stephen Hemminger sthemmin@microsoft.com Cc: K. Y. Srinivasan kys@microsoft.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- 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 @@ -1091,6 +1091,7 @@ 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 { @@ -1182,14 +1183,15 @@ 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,