Re: gprof cannot profile multi-threaded programs

[Kurt Roeckx]

On Tue, Jan 30, 2001 at 11:31:13PM -0600, Mohit Aron wrote:
> I analyzed the problem to be the following. Linux uses periodic SIGPROF signals
> for profiling (Linux doesn't use the profil system call used in other OS's like
> Solaris where the kernel does the profiling on behalf of the process). All
> profile information is collected in the context of the signal handler for the
> SIGPROF signal in Linux. Unfortunately, any thread that's created using
> pthread_create() does not get these periodic SIGPROF signals. Hence any thread
> other than the first thread is not profiled. The fix is to use setitimer()
> system call immediately in the thread startup function for any new thread to
> make the SIGPROF signal to be delivered at the designated interrupt frequency
> (every 10ms). With this fix, the profile produced by gprof reflects the overall
> computation done by all threads in the process. A more general fix would be
> to fix the kernel to make any new threads inherit the setitimer() settings
> for the parent thread.

You have the same problem when doing fork().  Only the parent
will get cpu usage info.  I have to call setitimer() too, to make
it work properly.

I complained about it a few days ago, but didn't get a reply yet.

Kurt