fpga_plugin: use time.Ticker instead of time.Sleep

Signed-off-by: Ed Bartosh <eduard.bartosh@intel.com>

Author: bart0sh

cmd/fpga_plugin/fpga_plugin.go

@@ -48,6 +48,9 @@ const (
 // When the device's firmware crashes the driver reports these values
 unhealthyAfuID = "ffffffffffffffffffffffffffffffff"
 unhealthyInterfaceID = "ffffffffffffffffffffffffffffffff"
+
+// Frequency of device scans
+scanFrequency = 5 * time.Second
 )
 
 type getDevTreeFunc func(devices []device) dpapi.DeviceTree
@@ -172,17 +175,33 @@ type devicePlugin struct {
 ignoreAfuIDs bool
 ignoreEmptyRegions bool
 annotationValue string
+
+scanTicker *time.Ticker
+scanDone chan bool
 }
 
 // newDevicePlugin returns new instance of devicePlugin
 func newDevicePlugin(mode string) (*devicePlugin, error) {
+var dp *devicePlugin
+var err error
+
 if _, err := os.Stat(sysfsDirectoryOPAE); os.IsNotExist(err) {
 if _, err = os.Stat(sysfsDirectoryDFL); os.IsNotExist(err) {
 return nil, fmt.Errorf("kernel driver is not loaded: neither %s nor %s sysfs entry exists", sysfsDirectoryOPAE, sysfsDirectoryDFL)
 }
-return newDevicePluginDFL(sysfsDirectoryDFL, devfsDirectory, mode)
+dp, err = newDevicePluginDFL(sysfsDirectoryDFL, devfsDirectory, mode)
+} else {
+dp, err = newDevicePluginOPAE(sysfsDirectoryOPAE, devfsDirectory, mode)
 }
-return newDevicePluginOPAE(sysfsDirectoryOPAE, devfsDirectory, mode)
+
+if err != nil {
+return nil, err
+}
+
+dp.scanTicker = time.NewTicker(scanFrequency)
+dp.scanDone = make(chan bool, 1) // buffered as we may send to it before Scan starts receiving from it
+
+return dp, nil
 }
 
 func (dp *devicePlugin) PostAllocate(response *pluginapi.AllocateResponse) error {
@@ -200,6 +219,7 @@ func (dp *devicePlugin) PostAllocate(response *pluginapi.AllocateResponse) error
 
 // Scan starts scanning FPGA devices on the host
 func (dp *devicePlugin) Scan(notifier dpapi.Notifier) error {
+defer dp.scanTicker.Stop()
 for {
 devTree, err := dp.scanFPGAs()
 if err != nil {
@@ -208,7 +228,11 @@ func (dp *devicePlugin) Scan(notifier dpapi.Notifier) error {
 
 notifier.Notify(devTree)
 
-time.Sleep(5 * time.Second)
+select {
+case <-dp.scanDone:
+return nil
+case <-dp.scanTicker.C:
+}
 }
 }