Re: [PATCH v3] PCI: Data corruption happening due to race condition

[Hari Vyas <hari.vyas@broadcom.com>]

On Thu, Jul 19, 2018 at 11:11 PM, Bjorn Helgaas <helgaas@kernel.org> wrote:
> On Tue, Jul 03, 2018 at 02:35:41PM +0530, Hari Vyas wrote:
>> When a pci device is detected, a variable is_added is set to
>> 1 in pci device structure and proc, sys entries are created.
>>
>> When a pci device is removed, first is_added is checked for one
>> and then device is detached with clearing of proc and sys
>> entries and at end, is_added is set to 0.
>>
>> is_added and is_busmaster are bit fields in pci_dev structure
>> sharing same memory location.
>>
>> A strange issue was observed with multiple times removal and
>> rescan of a pcie nvme device using sysfs commands where is_added
>> flag was observed as zero instead of one while removing device
>> and proc,sys entries are not cleared.  This causes issue in
>> later device addition with warning message "proc_dir_entry"
>> already registered.
>>
>> Debugging revealed a race condition between pcie core driver
>> enabling is_added bit(pci_bus_add_device()) and nvme driver
>> reset work-queue enabling is_busmaster bit (by pci_set_master()).
>> As both fields are not handled in atomic manner and that clears
>> is_added bit.
>>
>> Fix moves device addition is_added bit to separate private flag
>> variable and use different atomic functions to set and retrieve
>> device addition state. As is_added shares different memory
>> location so race condition is avoided.
>
> If/when you post a v4 of this, can you include the bugzilla URL
> right here, i.e.,
>
> Link: https://bugzilla.kernel.org/show_bug.cgi?id=200283
>> Signed-off-by: Hari Vyas <hari.vyas@broadcom.com>
>
> That way we can connect the commit with the bugzilla, which contains
> more information that may be useful in the future.
>
> Bjorn
Bit confused.  Do I  need  to change commit message for including bugzila link ?
Believe v3 should be Okay from code perspective time-being. Please confirm