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

[Alain Spineux]

On Wed, Oct 12, 2011 at 4:42 PM, JB <jb.1234abcd at gmail.com> wrote:
> 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

ps was freezing, I had to grep /proc/*/stat

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


The problem is not solved but if I disable debugging, the terminal is
not "flooded" and application finish without blocking.

Thanks for answering.

>
> JB
>
>
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