* 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 ?
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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