When I debug process with GDB I saw logs like:
[Detaching after fork from child process XXXX]
How can I stop print those log in gdb script?
Related
I have a program running on a remote machine which expects to receive SIGINT from the parent. That program needs to receive that signal to function correctly. Unfortunately, if I run that process remotely over SSH and send SIGINT, the ssh process itself traps and interrupts rather than forwarding the signal.
Here's an example of this behavior using GDB:
Running locally:
$ gdb
GNU gdb 6.3.50-20050815 (Apple version gdb-1344) (Fri Jul 3 01:19:56 UTC 2009)
...
This GDB was configured as "x86_64-apple-darwin".
^C
(gdb) Quit
^C
(gdb) Quit
^C
(gdb) Quit
Running remotely:
$ ssh foo.bar.com gdb
GNU gdb Red Hat Linux (6.3.0.0-1.159.el4rh)
...
This GDB was configured as "i386-redhat-linux-gnu".
(gdb) ^C
Killed by signal 2.
$
Can anybody suggest a way of working around this problem? The local ssh client is OpenSSH_5.2p1.
$ ssh -t foo.bar.com gdb
...
(gdb) ^C
Quit
Try signal SIGINT at the gdb prompt.
It looks like you're doing ctrl+c. The problem is that your terminal window is sending SIGINT to the ssh process running locally, not to the process on the remote system.
You'll have to specify a signal manually using the kill command or system call on the remote system.
or more conveniently using killall
$killall -INT gdb
Can you run a terminal on the remote machine and use kill -INT to send it the signal?
I have a simple C program that forks a process and then runs an executable.
I want to attach the child process to gdb.
I run the main program in a console and open another console to find the pid of the child process, then I start gdb with the following command:
gdb attach 12271
where 12271 is the child process id, but the attach fails with:
No such file or directory.
Any idea why?
Try one of these:
gdb -p 12271
gdb /path/to/exe 12271
gdb /path/to/exe
(gdb) attach 12271
The first argument should be the path to the executable program. So
gdb progname 12271
With a running instance of myExecutableName having a PID 15073:
hitting Tab twice after $ gdb myExecu in the command line, will automagically autocompletes to:
$ gdb myExecutableName 15073
and will attach gdb to this process. That's nice!
I execute the following strace command with the intention of getting data about PID 13221
strace -fF -tT -all -o abc.txt -p 13221
However when the command executes and finishes I get output like below :
Process 13221 attached with 12 threads - interrupt to quit
Process 13252 attached
Process 13253 attached (waiting for parent)
Process 13253 resumed (parent 13252 ready)
Process 13252 suspended
Process 13252 resumed
Process 13253 detached
Process 13252 detached
Process 13232 detached
Process 13228 detached
Process 13225 detached
Process 13222 detached
Process 13221 detached
What are these extra PID's ? Are these the children of 13221 ? Who is creating them ?
Thanks.
What are these extra PID's ? Are these the children of 13221 ?
It must have been threads of your program. You have used "-f" in strace and this is why threads are also monitored.
How to know which of these are threads
If you run ls /proc/<PID>/task for your process you will get PIDs of all threads in your process (including a PID of the main thread).
It is simpler to do when you need to get thread PIDs comparing with running pstack for the same process. pstack is actually a gdb script, it stops a process when attaches. So it is simpler just to run ls /proc/<PID>/task
I am writing one shell script in which I have parent process and it has child processes which are created by sleep & command. Now I wish to kill the parent process so that the child process will be also killed. I was able to do that this with below command:
trap "kill $$" SIGINT
trap 'kill -HUP 0' EXIT
trap 'kill $(jobs -p)' EXIT
These commands are working with kill [parent_process_ID] commands but if I use kill -9 [parent_process_ID] then only the parent process will be killed.
Please guide me further to achieve this functionality so that when I kill parent process with any command then child process should be also killed.
When you kill a process alone, it will not kill the children.
You have to send the signal to the process group if you want all processes for a given group to receive the signal.
kill -9 -parentpid
Otherwise, orphans will be linked to init.
Child can ask kernel to deliver SIGHUP (or other signal) when parent dies by specifying option PR_SET_PDEATHSIG in prctl() syscall like this:
prctl(PR_SET_PDEATHSIG, SIGHUP);
See man 2 prctl for details.
Sending the -9 signal (SIGKILL) to a program gives no chance for it to execute its own signal handlers (e.g., your trap statements). That is why the children don't get killed automatically. (In general, -9 gives no chance for the app to clean up after itself.) You have to use a weaker signal to kill it (such as SIGTERM.)
See man 7 signal for details.
I have used GAMESS for quantum computation in serial mode. I started to use it in parallel mode and it looks successful. But when I close my ssh terminal, the process is killed despite nohup command. In the log file, there is message "mpirun noticed that process rank 1 with PID 2254 on node * exited on signal 1 (Hangup)". How can I solve this problem? :(