On Thu, Sep 29, 2011 at 01:59:12PM -0400, Mathieu Desnoyers wrote:
> * Paul E. McKenney ([email protected]) wrote:
> > On Wed, Sep 28, 2011 at 04:34:32PM +0800, Lai Jiangshan wrote:
> > > Signed-off-by: Lai Jiangshan <[email protected]>
> > > ---
> > > urcu-call-rcu-impl.h | 6 ++++++
> > > 1 files changed, 6 insertions(+), 0 deletions(-)
> > >
> > > diff --git a/urcu-call-rcu-impl.h b/urcu-call-rcu-impl.h
> > > index 65c1c7a..3c68ae7 100644
> > > --- a/urcu-call-rcu-impl.h
> > > +++ b/urcu-call-rcu-impl.h
> > > @@ -686,6 +686,12 @@ void call_rcu_after_fork_child(void)
> > > default_call_rcu_data = NULL;
> > > (void)get_default_call_rcu_data();
> > >
> > > + /* Cleanup call_rcu_data pointers before used */
> > > + maxcpus = 0;
> > > + free(per_cpu_call_rcu_data);
> > > + per_cpu_call_rcu_data = NULL;
> >
> > Good catch! I would expect that the number of CPUs would be the
> > same for the child as it was for the parent, but doesn't hurt to
> > make the child start over.
> >
> > > + thread_call_rcu_data = NULL;
> >
> > Isn't thread_call_rcu_data already NULL due to the child being a new
> > thread and the C initialization-to-zero rules?
>
> #include <unistd.h>
> #include <stdio.h>
>
> int __thread a;
>
> int main()
> {
> int pid;
>
> a = 1;
> pid = fork();
> if (pid > 0) {
> printf("parent val %d\n", a);
> return 0;
> } else {
> printf("child val %d\n", a);
> return 0;
> }
> }
>
> compudj@thinkos:/tmp$ gcc -o test test.c
> compudj@thinkos:/tmp$ ./test
> parent val 1
> child val 1
>
> AFAIK, the c initialization to zero rules apply to exec(), not fork.
> Here we are taking care of after-fork in the child, in cases where the
> child is not doing an exec.
>
> Does that make more sense ?
I would think that the forked child would be a new thread, but obviously
not! I stand corrected.
Thanx, Paul
> Thanks,
>
> Mathieu
>
>
> >
> > Thanx, Paul
> >
> > > +
> > > /* Dispose of all of the rest of the call_rcu_data structures. */
> > > cds_list_for_each_entry_safe(crdp, next, &call_rcu_data_list, list) {
> > > if (crdp == default_call_rcu_data)
> > > --
> > > 1.7.4.4
> > >
>
> --
> Mathieu Desnoyers
> Operating System Efficiency R&D Consultant
> EfficiOS Inc.
> http://www.efficios.com
>
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