netdev - Re: [PATCH v2] PCI: lock each enable/disable num

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Date:   Mon, 9 Jan 2017 10:45:10 +1100
From:   Gavin Shan <gwshan@...ux.vnet.ibm.com>
To:     Emil Tantilov <emil.s.tantilov@...el.com>
Cc:     linux-pci@...r.kernel.org, intel-wired-lan@...ts.osuosl.org,
        alexander.h.duyck@...el.com, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] PCI: lock each enable/disable num_vfs operation in
 sysfs

On Fri, Jan 06, 2017 at 01:59:08PM -0800, Emil Tantilov wrote:
>Enabling/disabling SRIOV via sysfs by echo-ing multiple values
>simultaneously:
>
>echo 63 > /sys/class/net/ethX/device/sriov_numvfs&
>echo 63 > /sys/class/net/ethX/device/sriov_numvfs
>
>sleep 5
>
>echo 0 > /sys/class/net/ethX/device/sriov_numvfs&
>echo 0 > /sys/class/net/ethX/device/sriov_numvfs
>
>Results in the following bug:
>
>kernel BUG at drivers/pci/iov.c:495!
>invalid opcode: 0000 [#1] SMP
>CPU: 1 PID: 8050 Comm: bash Tainted: G   W   4.9.0-rc7-net-next #2092
>RIP: 0010:[<ffffffff813b1647>]
>	  [<ffffffff813b1647>] pci_iov_release+0x57/0x60
>
>Call Trace:
> [<ffffffff81391726>] pci_release_dev+0x26/0x70
> [<ffffffff8155be6e>] device_release+0x3e/0xb0
> [<ffffffff81365ee7>] kobject_cleanup+0x67/0x180
> [<ffffffff81365d9d>] kobject_put+0x2d/0x60
> [<ffffffff8155bc27>] put_device+0x17/0x20
> [<ffffffff8139c08a>] pci_dev_put+0x1a/0x20
> [<ffffffff8139cb6b>] pci_get_dev_by_id+0x5b/0x90
> [<ffffffff8139cca5>] pci_get_subsys+0x35/0x40
> [<ffffffff8139ccc8>] pci_get_device+0x18/0x20
> [<ffffffff8139ccfb>] pci_get_domain_bus_and_slot+0x2b/0x60
> [<ffffffff813b09e7>] pci_iov_remove_virtfn+0x57/0x180
> [<ffffffff813b0b95>] pci_disable_sriov+0x65/0x140
> [<ffffffffa00a1af7>] ixgbe_disable_sriov+0xc7/0x1d0 [ixgbe]
> [<ffffffffa00a1e9d>] ixgbe_pci_sriov_configure+0x3d/0x170 [ixgbe]
> [<ffffffff8139d28c>] sriov_numvfs_store+0xdc/0x130
>...
>RIP  [<ffffffff813b1647>] pci_iov_release+0x57/0x60
>
>Use the existing mutex lock to protect each enable/disable operation.
>
>-v2: move the existing lock from protecting the config of the IOV bus
>to protecting the writes to sriov_numvfs in sysfs without maintaining
>a "locked" version of pci_iov_add/remove_virtfn().
>As suggested by Gavin Shan <gwshan@...ux.vnet.ibm.com>
>
>CC: Alexander Duyck <alexander.h.duyck@...el.com>
>Signed-off-by: Emil Tantilov <emil.s.tantilov@...el.com>
>---

Reviewed-by: Gavin Shan <gwshan@...ux.vnet.ibm.com>