linux-kernel - RE: [PATCH] PCI: hv: Fix a __local_bh_enable_ip warning in hv_compose_msi

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Date:   Thu, 7 Jun 2018 00:14:39 +0000
From:   Dexuan Cui <decui@...rosoft.com>
To:     Haiyang Zhang <haiyangz@...rosoft.com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
        KY Srinivasan <kys@...rosoft.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        "olaf@...fle.de" <olaf@...fle.de>,
        "apw@...onical.com" <apw@...onical.com>,
        "jasowang@...hat.com" <jasowang@...hat.com>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "driverdev-devel@...uxdriverproject.org" 
        <driverdev-devel@...uxdriverproject.org>,
        "vkuznets@...hat.com" <vkuznets@...hat.com>,
        "marcelo.cerri@...onical.com" <marcelo.cerri@...onical.com>
Subject: RE: [PATCH] PCI: hv: Fix a __local_bh_enable_ip warning in
 hv_compose_msi_msg()

> From: Haiyang Zhang
> Sent: Friday, May 25, 2018 12:52
> To: Dexuan Cui <decui@...rosoft.com>; Lorenzo Pieralisi
> <lorenzo.pieralisi@....com>; Bjorn Helgaas <bhelgaas@...gle.com>;
> linux-pci@...r.kernel.org; KY Srinivasan <kys@...rosoft.com>; Stephen
> Hemminger <sthemmin@...rosoft.com>; olaf@...fle.de;
> apw@...onical.com; jasowang@...hat.com
> Cc: linux-kernel@...r.kernel.org; driverdev-devel@...uxdriverproject.org;
> vkuznets@...hat.com; marcelo.cerri@...onical.com
> Subject: RE: [PATCH] PCI: hv: Fix a __local_bh_enable_ip warning in
> hv_compose_msi_msg()
> 
> > From: Dexuan Cui
> > Sent: Tuesday, May 22, 2018 8:18 PM
> > To: Lorenzo Pieralisi <lorenzo.pieralisi@....com>; Bjorn Helgaas
> > <bhelgaas@...gle.com>; linux-pci@...r.kernel.org; KY Srinivasan
> > <kys@...rosoft.com>; Stephen Hemminger <sthemmin@...rosoft.com>;
> > olaf@...fle.de; apw@...onical.com; jasowang@...hat.com
> > Cc: linux-kernel@...r.kernel.org; driverdev-devel@...uxdriverproject.org;
> > Haiyang Zhang <haiyangz@...rosoft.com>; vkuznets@...hat.com;
> > marcelo.cerri@...onical.com
> > 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@...rosoft.com>
> > Cc: <stable@...r.kernel.org>
> > Cc: Stephen Hemminger <sthemmin@...rosoft.com>
> > Cc: K. Y. Srinivasan <kys@...rosoft.com>
> > ---
> 
> Reviewed-by: Haiyang Zhang <haiyangz@...rosoft.com>
> 
> Thanks you.

Hi Lorenzo,

Can I have your reply to this patch?

-- Dexuan