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* [PATCH] PCI: hv: Fix a __local_bh_enable_ip warning in hv_compose_msi_msg()
@ 2018-05-23  0:18 Dexuan Cui
  2018-05-25 19:51 ` Haiyang Zhang
  0 siblings, 1 reply; 8+ messages in thread
From: Dexuan Cui @ 2018-05-23  0:18 UTC (permalink / raw)
  To: Lorenzo Pieralisi, Bjorn Helgaas, linux-pci, KY Srinivasan,
	Stephen Hemminger, olaf, apw, jasowang
  Cc: marcelo.cerri, vkuznets, Haiyang Zhang, driverdev-devel, linux-kernel

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.

With CONFIG_PROVE_LOCKING=y in the latest mainline, or
old kernels that don't have commit f71b74bca637 ("irq/softirqs: Use lockdep
to assert IRQs are disabled/enabled"), it turns out can we trigger a warning
at the beginning of __local_bh_enable_ip(), because the upper layer
irq code can call hv_compose_msi_msg() with local irqs disabled.

Let's fix the warning by switching to local_irq_save()/restore(). This
is not an issue because hv_pci_onchannelcallback() is not slow, and it
not a hot path.

Fixes: de0aa7b2f97d ("PCI: hv: Fix 2 hang issues in hv_compose_msi_msg()")
Signed-off-by: Dexuan Cui <>
Cc: <>
Cc: Stephen Hemminger <>
Cc: K. Y. Srinivasan <>

A trimmed version of the warning is:

  IRQs not enabled as expected
  WARNING: CPU: 0 PID: 408 at kernel/softirq.c:162 __local_bh_enable_ip+0xb0/0xe0
  Call Trace:
   hv_compose_msi_msg+0x209/0x462 [pci_hyperv]
  mlx4_init_eq_table+0x3c3/0x5f0 [mlx4_core]
  mlx4_setup_hca+0x1db/0x750 [mlx4_core]
  mlx4_load_one+0xad2/0x13b0 [mlx4_core]
  mlx4_init_one+0x578/0x710 [mlx4_core]

 drivers/pci/host/pci-hyperv.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/drivers/pci/host/pci-hyperv.c b/drivers/pci/host/pci-hyperv.c
index 50cdefe..ad6a64d 100644
--- a/drivers/pci/host/pci-hyperv.c
+++ b/drivers/pci/host/pci-hyperv.c
@@ -1051,6 +1051,7 @@ static u32 hv_compose_msi_req_v2(
 static void hv_compose_msi_msg(struct irq_data *data, struct msi_msg *msg)
+	unsigned long flags;
 	struct irq_cfg *cfg = irqd_cfg(data);
 	struct hv_pcibus_device *hbus;
 	struct hv_pci_dev *hpdev;
@@ -1148,14 +1149,14 @@ 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.
-		local_bh_disable();
+		local_irq_save(flags);
 		if (hbus->hdev->channel->target_cpu == smp_processor_id())
-		local_bh_enable();
+		local_irq_restore(flags);
 		if (hpdev->state == hv_pcichild_ejecting) {

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^ permalink raw reply	[flat|nested] 8+ messages in thread

end of thread, other threads:[~2018-06-30 18:13 UTC | newest]

Thread overview: 8+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2018-05-23  0:18 [PATCH] PCI: hv: Fix a __local_bh_enable_ip warning in hv_compose_msi_msg() Dexuan Cui
2018-05-25 19:51 ` Haiyang Zhang
2018-06-07  0:14   ` Dexuan Cui
2018-06-13 20:32     ` Dexuan Cui
2018-06-13 22:15       ` Bjorn Helgaas
2018-06-13 22:50         ` Dexuan Cui
2018-06-29  9:39           ` Lorenzo Pieralisi
2018-06-30 18:13             ` Dexuan Cui

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