Dear Valgrind Developers:
My name is Rui Gu, a student from Columbia University. Thanks for building and
maintaining such great tool!
Right now, we’re trying to enable Helgrind on UserModeLinux(UML).
We’ve encountered a problem and want to get a clue about the best way of
solving it.
Let me put our basic understanding of Valgrind and the problems we encountered
here.
Helgrind:
For a thread that is created by pthread_create(). Valgrind first intercept
pthread_create() in hg_intercept.c for some threading info registration. Then,
coregrind will intercept clone() in syswrap-x86-linux.c to monitor and control
the thread creation and execution. Valgrind also supports some self-implemented
synchronization primitives by using ANNOTATION.
Question:
In short, we want to ask what’s the most legitimate way of supporting user
level thread scheduling system?
The detailed question goes from here:
The problem is that UML will have its own user level threading systems. They
use kernel_thread() to create threads and scheduling them on the user level.
The code is like this.
int kernel_thread(int (*fn)(void* ), void * arg, unsigned long flags)
{
int pid;
current->thread.request.u.thread.proc = fn;
current->thread.request.u.thread.arg = arg;
pid = do_fork(CLONE_VM | CLONE_UNTRACED | flags, 0,
¤t->thread.regs, 0, NULL, NULL);
return pid;
}
So, our guess is, in order to let Valgrind detect, monitor and control these
threads. We need to first intercept kernel_thread() in hg_intercept.c and then
intercept do_fork() in coregrind. Instead of letting coregrind calls clone
internally, we’ll have to let Valgrind call do_fork() of UML.
The problem is right now, it’s kind of hard and strange to let coregrind to
call a function within UML. Because coregrind is not supposed to see any guest
program APIs and thus there isn’t any related API of doing it. So we’re
wondering r we doing it in the right way?
Thanks in advance for your kind support.
Rui------------------------------------------------------------------------------
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