Messages in this thread | | | Date | Wed, 3 Oct 2007 11:06:10 -0700 | From | Randy Dunlap <> | Subject | Re: [PATCH 1/3] Introduce the dummy_pid |
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On Wed, 03 Oct 2007 18:19:01 +0400 Pavel Emelyanov wrote:
> This is a pid which is attached to tasks when they detach > their pids. This is done in detach_pid() and transfer_pid(). > The pid_alive() check is changed to reflect this fact. > > Signed-off-by: Pavel Emelyanov <xemul@openvz.org> > > --- > > diff --git a/include/linux/sched.h b/include/linux/sched.h > index 4f21af1..e17b8f8 100644 > --- a/include/linux/sched.h > +++ b/include/linux/sched.h > @@ -1286,9 +1286,11 @@ static inline pid_t task_ppid_nr_ns(stru > * If pid_alive fails, then pointers within the task structure > * can be stale and must not be dereferenced. > */ > +extern struct pid dummy_pid; > + > static inline int pid_alive(struct task_struct *p) > { > - return p->pids[PIDTYPE_PID].pid != NULL; > + return p->pids[PIDTYPE_PID].pid != &dummy_pid; > } > > /** > diff --git a/kernel/pid.c b/kernel/pid.c > index d7388d7..b7a11cf 100644 > --- a/kernel/pid.c > +++ b/kernel/pid.c > @@ -81,6 +81,17 @@ struct pid_namespace init_pid_ns = { > }; > EXPORT_SYMBOL_GPL(init_pid_ns); > > +struct pid dummy_pid = { > + .count = ATOMIC_INIT(1), > + .numbers = { { > + .nr = 0, /* this is what pid_nr will return > + * for tasks with no pids > + */ > + .ns = &init_pid_ns, > + }, } > +}; > +EXPORT_SYMBOL(dummy_pid);
Why is the EXPORT_SYMBOL() needed? IOW, is some loadable module going to use this?
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