I've got it! That's what will work:
struct task_struct {
...
struct beancounter *exec_bc;
struct beancounter *tmp_exec_bc; /* is set to NULL on
* tsk creation
*/
};
struct beancounter get_exec_bc(void)
{
if (current->tmp_exec_bc)
return current->tmp_exec_bc;
return rcu_dereference(current->exec_bc);
}
struct beancounter set_tmp_exec_bc(struct beancounter *new)
{
struct beancounter *old;
old = current->tmp_exec_bc;
current->tmp_exec_bc = new;
return old;
}
void reset_tmp_exec_bc(struct beancounter *expected_old)
{
BUG_ON(current->tmp_exec_bc != expected_old);
current->tmp_exec_bc = NULL;
}
void move_task(struct task_struct *tsk, struct beancounter *bc)
{
struct beancounter *old;
mutex_lock(&tsk_move_mutex);
old = tsk->exec_bc;
get_bc(bc);
rcu_assign_pointer(current->exec_bc, bc);
syncronize_rcu();
mutex_unlock(&tsk_move_mutex);
bc_put(old);
}
I will implement this in the next beancounter patches.
Thanks for discussion :)
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