"echo hello > /dev/pts/2" is blocking

[JB]

Alain Spineux <aspineux <at> gmail.com> writes:

> 
> I have a FUSE program in debug mode displaying a lot of debug messages
> on the terminal.
> After hours the program "freeze" and the terminal looks blocked.
> The terminal don't react to key press, nor CTRL-C nor CTRL-Z
> 
> Using gdb, I get 31 threads, the 25 looks strange.
> It looks to be blocking on a write() system call while displaying a
> debug message to the terminal
> Then I tried
> # echo hello > /dev/pts/2
> and it's blocking too !
> Other pts on the same host don't block
> 
> How can a pts block ? Probably a problem with ssh or sshd. Using
> strace, I can see both waiting on a select()
> and not reacting to a key press or to the echo hello > /dev/pts/2. The
> ssh client is running on a fedora 11
> 
> What next ?
> 
> I'm running fedora 14 on x64, but get exactly the same on a f14 i386.
> I'm running the same test on centos-6 x64 just now
> 
> Regards

I would say take a look at pertinent info (from another terminal on that
machine):
$ w
$ ps aux |grep -i pts

Threads:
$ ps -eLf |grep -i pts
$ ps axms |grep -i pts
$ man ps         # signals: PENDING or BLOCKED or IGNORED or CAUGHT
$ man select

JB