From: Lukas Wunner <lukas@wunner.de>
To: Sinan Kaya <okaya@kernel.org>
Cc: Ethan Zhao <haifeng.zhao@intel.com>,
bhelgaas@google.com, oohall@gmail.com, ruscur@russell.cc,
andriy.shevchenko@linux.intel.com, stuart.w.hayes@gmail.com,
mr.nuke.me@gmail.com, mika.westerberg@linux.intel.com,
Keith Busch <keith.busch@intel.com>,
linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org,
pei.p.jia@intel.com, ashok.raj@linux.intel.com,
sathyanarayanan.kuppuswamy@intel.com
Subject: Re: [PATCH 2/5 V2] PCI: pciehp: check and wait port status out of DPC before handling DLLSC and PDC
Date: Tue, 29 Sep 2020 10:18:00 +0200 [thread overview]
Message-ID: <20200929081800.GA15858@wunner.de> (raw)
In-Reply-To: <f2c9e3db-2027-f669-fcdd-fbc80888b934@kernel.org>
On Sun, Sep 27, 2020 at 11:27:46AM -0400, Sinan Kaya wrote:
> On 9/26/2020 11:28 PM, Ethan Zhao wrote:
> > --- a/drivers/pci/hotplug/pciehp_hpc.c
> > +++ b/drivers/pci/hotplug/pciehp_hpc.c
> > @@ -710,8 +710,10 @@ static irqreturn_t pciehp_ist(int irq, void *dev_id)
> > down_read(&ctrl->reset_lock);
> > if (events & DISABLE_SLOT)
> > pciehp_handle_disable_request(ctrl);
> > - else if (events & (PCI_EXP_SLTSTA_PDC | PCI_EXP_SLTSTA_DLLSC))
> > + else if (events & (PCI_EXP_SLTSTA_PDC | PCI_EXP_SLTSTA_DLLSC)) {
> > + pci_wait_port_outdpc(pdev);
> > pciehp_handle_presence_or_link_change(ctrl, events);
> > + }
> > up_read(&ctrl->reset_lock);
>
> This looks like a hack TBH.
>
> Lukas, Keith;
>
> What is your take on this?
> Why is device lock not protecting this situation?
>
> Is there a lock missing in hotplug driver?
According to Ethan's commit message, there are two issues here:
One, that pciehp may remove a device even though DPC recovered the error,
and two, that a null pointer deref occurs.
The latter is most certainly not a locking issue but failure of DPC
to hold a reference on the pci_dev.
Thanks,
Lukas
next prev parent reply other threads:[~2020-09-29 8:27 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-27 3:28 [PATCH 0/5 V2] Fix DPC hotplug race and enhance error handling Ethan Zhao
2020-09-27 3:28 ` [PATCH 1/5 V2] PCI: define a function to check and wait till port finish DPC handling Ethan Zhao
2020-09-27 6:23 ` Christoph Hellwig
2020-09-27 6:43 ` Zhao, Haifeng
2020-09-29 2:32 ` Ethan Zhao
2020-09-27 3:28 ` [PATCH 2/5 V2] PCI: pciehp: check and wait port status out of DPC before handling DLLSC and PDC Ethan Zhao
2020-09-27 15:27 ` Sinan Kaya
2020-09-28 2:01 ` Zhao, Haifeng
2020-09-28 11:10 ` Sinan Kaya
2020-09-28 16:43 ` Sinan Kaya
2020-09-28 16:44 ` Kuppuswamy, Sathyanarayanan
2020-09-29 2:28 ` Ethan Zhao
2020-09-29 2:50 ` Ethan Zhao
2020-09-29 8:18 ` Lukas Wunner [this message]
2020-09-29 9:46 ` Ethan Zhao
2020-09-29 10:07 ` Lukas Wunner
2020-09-30 2:20 ` Ethan Zhao
2020-09-27 3:28 ` [PATCH 3/5 V2] PCI/ERR: get device before call device driver to avoid NULL pointer reference Ethan Zhao
2020-09-27 3:28 ` [PATCH 4/5 V2] PCI: only return true when dev io state is really changed Ethan Zhao
2020-09-27 4:16 ` Joe Perches
2020-09-27 5:12 ` Zhao, Haifeng
2020-09-27 3:28 ` [PATCH 5/5 V2] PCI/ERR: don't mix io state not changed and no driver together Ethan Zhao
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