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Is there any way of setting the name of a thread in Linux?
My main purpose is it would be helpful while debugging, and also nice if that name was exposed through e.g. /proc/$PID/task/$TID/...
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The pthread_setname_np() function sets the name of the target thread. The buffer specified by name must contain a null-terminated string of 15 characters or less in length (not including the NULL).
You can give a name to a thread by using setName() method of Thread class. You can also retrieve the name of a thread using getName() method of a Thread class. These two methods are public and final.
With pthreads I would do: pthread_setname_np(pthread_self(), "thread_name");
The pthread_join() function provides a simple mechanism allowing an application to wait for a thread to terminate. After the thread terminates, the application may then choose to clean up resources that were used by the thread.
As of glibc v2.12, you can use pthread_setname_np and pthread_getname_np to set/get the thread name.
These interfaces are available on a few other POSIX systems (BSD, QNX, Mac) in various slightly different forms.
Setting the name will be something like this:
#include <pthread.h> // or maybe <pthread_np.h> for some OSes // Linux int pthread_setname_np(pthread_t thread, const char *name); // NetBSD: name + arg work like printf(name, arg) int pthread_setname_np(pthread_t thread, const char *name, void *arg); // FreeBSD & OpenBSD: function name is slightly different, and has no return value void pthread_set_name_np(pthread_t tid, const char *name); // Mac OS X: must be set from within the thread (can't specify thread ID) int pthread_setname_np(const char*); And you can get the name back:
#include <pthread.h> // or <pthread_np.h> ? // Linux, NetBSD: int pthread_getname_np(pthread_t th, char *buf, size_t len); // some implementations don't have a safe buffer (see MKS/IBM below) int pthread_getname_np(pthread_t thread, const char **name); int pthread_getname_np(pthread_t thread, char *name); // FreeBSD & OpenBSD: dont' seem to have getname/get_name equivalent? // but I'd imagine there's some other mechanism to read it directly for say gdb // Mac OS X: int pthread_getname_np(pthread_t, char*, size_t); As you can see it's not completely portable between POSIX systems, but as far as I can tell across linux it should be consistent. Apart from Mac OS X (where you can only do it from within the thread), the others are at least simple to adapt for cross-platform code.
Sources:
/Developer/SDKs/MacOSX10.7.sdk/usr/include/pthread.h
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Use the prctl(2) function with the option PR_SET_NAME (see the docs).
Note that old versions of the docs are a bit confusing. They say
Set the process name for the calling process
but since threads are light weight processes (LWP) on Linux, one thread is one process in this case.
You can see the thread name with ps -o cmd or with:
cat /proc/$PID/task/$TID/comm or in between the () of cat /proc/$PID/task/$TID/stat:
4223 (kjournald) S 1 1 1 0... or from GDB info threads between double quotes:
* 1 Thread 0x7ffff7fc7700 (LWP 6575) "kjournald" 0x00007ffff78bc30d in nanosleep () at ../sysdeps/unix/syscall-template.S:84 If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
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