arduino ide error msg

Binary sketch size: 24,138 bytes (of a 258,048 byte maximum)
processing.app.SerialException: Error opening serial port '/dev/ttyACM0'.
	at processing.app.Serial.<init>(Serial.java:178)
	at processing.app.Serial.<init>(Serial.java:77)
	at processing.app.debug.Uploader.flushSerialBuffer(Uploader.java:77)
	at processing.app.debug.AvrdudeUploader.uploadViaBootloader(AvrdudeUploader.java:174)
	at processing.app.debug.AvrdudeUploader.uploadUsingPreferences(AvrdudeUploader.java:67)
	at processing.app.Sketch.upload(Sketch.java:1671)
	at processing.app.Sketch.exportApplet(Sketch.java:1627)
	at processing.app.Sketch.exportApplet(Sketch.java:1599)
	at processing.app.Editor$DefaultExportHandler.run(Editor.java:2380)
	at java.lang.Thread.run(Thread.java:722)
Caused by: gnu.io.UnsupportedCommOperationException: Invalid Parameter
	at gnu.io.RXTXPort.setSerialPortParams(RXTXPort.java:171)
	at processing.app.Serial.<init>(Serial.java:163)
	... 9 more
processing.app.debug.RunnerException: Error opening serial port '/dev/ttyACM0'.
	at processing.app.debug.Uploader.flushSerialBuffer(Uploader.java:101)
	at processing.app.debug.AvrdudeUploader.uploadViaBootloader(AvrdudeUploader.java:174)
	at processing.app.debug.AvrdudeUploader.uploadUsingPreferences(AvrdudeUploader.java:67)
	at processing.app.Sketch.upload(Sketch.java:1671)
	at processing.app.Sketch.exportApplet(Sketch.java:1627)
	at processing.app.Sketch.exportApplet(Sketch.java:1599)
	at processing.app.Editor$DefaultExportHandler.run(Editor.java:2380)
	at java.lang.Thread.run(Thread.java:722)