Re: [uml-devel] making uml work with smp

[BlaisorBlade <bla...@ya...>]

Alle 13:21, gioved=EC 10 giugno 2004, Vincent Guffens ha scritto:
> Hi,

> The only changes that have to be made to compile with SMP is
>
> *add the folowing to  arch/um/config.in
>
>   define_bool CONFIG_SMP $CONFIG_UML_SMP
> +int 'Number of CPUs' CONFIG_NR_CPUS 1
>
> *change this line in arch/um/kernel/um_arch.c
> -int ncpus =3D 1;
> +int ncpus =3D 4;

No, please at least make CONFIG_NR_CPUS =3D=3D ncpus, PLEASE!

> *turn it on in the kernel config

Well, watch this code in the patch:

+void switch_mm_skas(int mm_fd)
+{
+       int err;
+
+#warning need cpu pid in switch_mm_skas
+       err =3D ptrace(PTRACE_SWITCH_MM, userspace_pid[0], 0, mm_fd);
+       if(err)
+               panic("switch_mm_skas - PTRACE_SWITCH_MM failed, errno =3D=
=20
%d\n",
+                     errno);
+}
+
+void kill_off_processes_skas(void)
+{
+#warning need to loop over userspace_pids in kill_off_processes_skas
+       os_kill_process(userspace_pid[0], 1);
+}

userspace_pid[] is the array of the pids of the "userspace threads" (the=20
threads in T state, i.e. ptraced, which run the actual code of the guest=20
userspace). The warning complain that they should act onto the whole array.

Here, instead, you must use smp_processor_id() to determine which CPU you r=
un=20
on and then use it as userspace_pid index.

+int external_pid_skas(struct task_struct *task)
+{
+#warning Need to look up userspace_pid by cpu
+       return(userspace_pid[0]);
+}
+
+int thread_pid_skas(struct thread_struct *thread)
+{
+#warning Need to look up userspace_pid by cpu
+       return(userspace_pid[0]);
+}

Check any other usage of userspace_pid (on the code, not by debugging) and=
=20
you've started solving the crashes. Then you can try again to see if there =
is=20
still something.

Bye
=2D-=20
Paolo Giarrusso, aka Blaisorblade
Linux registered user n. 292729