#! /bin/sh

//bin/true && exec stap -g $0 ${1+"$@"}

# Override NPTL's "ulimit -s" based default stacksize for new pthreads.
# Invoke with   # stap -g threadstacks.stp -Gsize=NNNN
#    ... add "-x PID" or "-c CMD", unless you wish to target the entire system.
#    ... due to a possible stap bug, might need to add "-d BINARY" for relevant binaries
#
# NB: 'size' needs to be a sufficiently large multiple of the OS pagesize,
# else pthread_create(3) will fail.
#
# See also http://sourceware.org/ml/libc-alpha/2013-01/msg00572.html

global size = 0;

probe process("/lib*/libpthread.so.*").function("allocate_stack") {
    old_size = @choose_defined($__default_stacksize,
			       $__default_pthread_attr->stacksize)
    if ((size != 0) && (old_size != size)) {  /* requested but not yet changed */
	/* change it and report */
	if (@defined($__default_stacksize)) {
            $__default_stacksize = size
	    printf("%s[%d] overwrote __default_stacksize@%p (%d->%d)\n",
		   execname(), tid(), &$__default_stacksize, old_size, size)
	}
	else {
	    $__default_pthread_attr->stacksize = size
	    printf("%s[%d] overwrote __default_stacksize@%p (%d->%d)\n",
		   execname(), tid(), &$__default_pthread_attr->stacksize,
		   old_size, size)
	}
    }
}
