iavf: do not override the adapter state in the watchdog task

The iavf watchdog task overrides adapter->state to __IAVF_RESETTING
when it detects a pending reset. Then schedules iavf_reset_task() which
takes care of the reset.

The reset task is capable of handling the reset without changing
adapter->state. In fact we lose the state information when the watchdog
task prematurely changes the adapter state. This may lead to a crash if
instead of the reset task the iavf_remove() function gets called before
the reset task.
In that case (if we were in state __IAVF_RUNNING previously) the
iavf_remove() function triggers iavf_close() which fails to close the
device because of the incorrect state information.

This may result in a crash due to pending interrupts.
kernel BUG at drivers/pci/msi.c:357!
[...]
Call Trace:
 [<ffffffffbddf24dd>] pci_disable_msix+0x3d/0x50
 [<ffffffffc08d2a63>] iavf_reset_interrupt_capability+0x23/0x40 [iavf]
 [<ffffffffc08d312a>] iavf_remove+0x10a/0x350 [iavf]
 [<ffffffffbddd3359>] pci_device_remove+0x39/0xc0
 [<ffffffffbdeb492f>] __device_release_driver+0x7f/0xf0
 [<ffffffffbdeb49c3>] device_release_driver+0x23/0x30
 [<ffffffffbddcabb4>] pci_stop_bus_device+0x84/0xa0
 [<ffffffffbddcacc2>] pci_stop_and_remove_bus_device+0x12/0x20
 [<ffffffffbddf361f>] pci_iov_remove_virtfn+0xaf/0x160
 [<ffffffffbddf3bcc>] sriov_disable+0x3c/0xf0
 [<ffffffffbddf3ca3>] pci_disable_sriov+0x23/0x30
 [<ffffffffc0667365>] i40e_free_vfs+0x265/0x2d0 [i40e]
 [<ffffffffc0667624>] i40e_pci_sriov_configure+0x144/0x1f0 [i40e]
 [<ffffffffbddd5307>] sriov_numvfs_store+0x177/0x1d0
Code: 00 00 e8 3c 25 e3 ff 49 c7 86 88 08 00 00 00 00 00 00 5b 41 5c 41 5d 41 5e 41 5f 5d c3 48 8b 7b 28 e8 0d 44
RIP  [<ffffffffbbbf1068>] free_msi_irqs+0x188/0x190

The solution is to not touch the adapter->state in iavf_watchdog_task()
and let the reset task handle the state transition.
Signed-off-by: Stefan Assmann <sassmann@kpanic.de>
Tested-by: Konrad Jankowski <konrad0.jankowski@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>

drivers/net/ethernet/intel/iavf/iavf_main.c

@@ -1988,7 +1988,6 @@ static void iavf_watchdog_task(struct work_struct *work)
 		/* check for hw reset */
 	reg_val = rd32(hw, IAVF_VF_ARQLEN1) & IAVF_VF_ARQLEN1_ARQENABLE_MASK;
 	if (!reg_val) {
-		adapter->state = __IAVF_RESETTING;
 		adapter->flags |= IAVF_FLAG_RESET_PENDING;
 		adapter->aq_required = 0;
 		adapter->current_op = VIRTCHNL_OP_UNKNOWN;