igc: Fix infinite loop in release_swfw_sync

An infinite loop may occur if we fail to acquire the HW semaphore,
which is needed for resource release.
This will typically happen if the hardware is surprise-removed.
At this stage there is nothing to do, except log an error and quit.

Fixes: c0071c7a ("igc: Add HW initialization code")
Suggested-by: NDima Ruinskiy <dima.ruinskiy@intel.com>
Signed-off-by: NSasha Neftin <sasha.neftin@intel.com>
Tested-by: NNaama Meir <naamax.meir@linux.intel.com>
Signed-off-by: NTony Nguyen <anthony.l.nguyen@intel.com>

drivers/net/ethernet/intel/igc/igc_i225.c

@@ -156,8 +156,15 @@ void igc_release_swfw_sync_i225(struct igc_hw *hw, u16 mask)
 {
 	u32 swfw_sync;
 
-	while (igc_get_hw_semaphore_i225(hw))
-		; /* Empty */
+	/* Releasing the resource requires first getting the HW semaphore.
+	 * If we fail to get the semaphore, there is nothing we can do,
+	 * except log an error and quit. We are not allowed to hang here
+	 * indefinitely, as it may cause denial of service or system crash.
+	 */
+	if (igc_get_hw_semaphore_i225(hw)) {
+		hw_dbg("Failed to release SW_FW_SYNC.\n");
+		return;
+	}
 
 	swfw_sync = rd32(IGC_SW_FW_SYNC);
 	swfw_sync &= ~mask;