Recently, whenever I run jackd, it gives me the following message

$ jackd -d alsa -d hw:0
no message buffer overruns
jackd 0.116.1
Copyright 2001-2005 Paul Davis and others.
jackd comes with ABSOLUTELY NO WARRANTY
This is free software, and you are welcome to redistribute it
under certain conditions; see the file COPYING for details

JACK compiled with System V SHM support.
loading driver ..
creating alsa driver ... hw:0|hw:0|1024|2|48000|0|0|nomon|swmeter|-|32bit
control device hw:0
ALSA: Cannot open PCM device alsa_pcm for playback. Falling back to capture-only mode
cannot load driver module alsa

That is strange that I can use it normally for a while. After a hard and deeply research I cannot even find answers!

But I just succeed with the following command:

$ jackd -d alsa -d hw:2
no message buffer overruns
jackd 0.116.1
Copyright 2001-2005 Paul Davis and others.
jackd comes with ABSOLUTELY NO WARRANTY
This is free software, and you are welcome to redistribute it
under certain conditions; see the file COPYING for details

JACK compiled with System V SHM support.
loading driver ..
creating alsa driver ... hw:2|hw:2|1024|2|48000|0|0|nomon|swmeter|-|32bit
control device hw:2
configuring for 48000Hz, period = 1024 frames (21.3 ms), buffer = 2 periods
ALSA: final selected sample format for capture: 16bit little-endian
ALSA: use 2 periods for capture
ALSA: final selected sample format for playback: 16bit little-endian
ALSA: use 2 periods for playback

WTF! is this problem so stupid?