RE: [PATCH] PCI: hv: Fix a __local_bh_enable_ip warning in hv_compose_msi_msg()

[Haiyang Zhang]

> -----Original Message-----
> From: Dexuan Cui
> Sent: Tuesday, May 22, 2018 8:18 PM
> To: Lorenzo Pieralisi <lorenzo.pieralisi@xxxxxxx>; Bjorn Helgaas
> <bhelgaas@xxxxxxxxxx>; linux-pci@xxxxxxxxxxxxxxx; KY Srinivasan
> <kys@xxxxxxxxxxxxx>; Stephen Hemminger <sthemmin@xxxxxxxxxxxxx>;
> olaf@xxxxxxxxx; apw@xxxxxxxxxxxxx; jasowang@xxxxxxxxxx
> Cc: linux-kernel@xxxxxxxxxxxxxxx; driverdev-devel@xxxxxxxxxxxxxxxxxxxxxx;
> Haiyang Zhang <haiyangz@xxxxxxxxxxxxx>; vkuznets@xxxxxxxxxx;
> marcelo.cerri@xxxxxxxxxxxxx
> Subject: [PATCH] PCI: hv: Fix a __local_bh_enable_ip warning in
> hv_compose_msi_msg()
> 
> 
> 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 <decui@xxxxxxxxxxxxx>
> Cc: <stable@xxxxxxxxxxxxxxx>
> Cc: Stephen Hemminger <sthemmin@xxxxxxxxxxxxx>
> Cc: K. Y. Srinivasan <kys@xxxxxxxxxxxxx>
> ---

Reviewed-by: Haiyang Zhang <haiyangz@xxxxxxxxxxxxx>

Thanks you.