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    SubjectRe: [PATCH 6/7] module: add two missing synchronize_sched()
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    On Thu, 2012-03-15 at 22:49 +0800, Cong Wang wrote:
    > In RCU doc, it said synchronize_sched() is used to mark the end
    > of update, so two synchronize_sched() are missing after
    > module list add/del.
    >
    > Cc: Eric Dumazet <eric.dumazet@gmail.com>
    > Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
    > Cc: Rusty Russell <rusty@rustcorp.com.au>
    > Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
    > ---
    > kernel/module.c | 2 ++
    > 1 files changed, 2 insertions(+), 0 deletions(-)
    >
    > diff --git a/kernel/module.c b/kernel/module.c
    > index 06e7dc5..2e7a5c5 100644
    > --- a/kernel/module.c
    > +++ b/kernel/module.c
    > @@ -1775,6 +1775,7 @@ static void free_module(struct module *mod)
    > mutex_lock(&module_mutex);
    > stop_machine(__unlink_module, mod, NULL);
    > mutex_unlock(&module_mutex);
    > + synchronize_sched();
    > mod_sysfs_teardown(mod);
    >
    > /* Remove dynamic debug info */
    > @@ -2928,6 +2929,7 @@ static struct module *load_module(void __user *umod,
    > module_bug_finalize(info.hdr, info.sechdrs, mod);
    > list_add_rcu(&mod->list, &modules);
    > mutex_unlock(&module_mutex);
    > + synchronize_sched();
    >
    > /* Module is ready to execute: parsing args may do that. */
    > err = parse_args(mod->name, mod->args, mod->kp, mod->num_kp, NULL);

    Have a look at stop_machine() first

    after list_add_rcu(), there is absolutely no such requirement.





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