On Wed, 17 Mar 2021 18:25:28 +0800 Li Huafei <[email protected]> wrote:
> The unregistered ftrace_ops may be freed by the caller, so we should use > rcu_assign_pointer() in remove_ftrace_ops() to remove the ftrace_ops, > which ensures that no more users will reference the ftrace_ops after > synchronize_rcu() is called. The patch is fine, but we don't use synchronize_rcu() to protect the list. We use synchronize_rcu_tasks(). -- Steve > > Signed-off-by: Li Huafei <[email protected]> > --- > kernel/trace/ftrace.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c > index 4d8e35575549..2e315a145d20 100644 > --- a/kernel/trace/ftrace.c > +++ b/kernel/trace/ftrace.c > @@ -282,7 +282,7 @@ static int remove_ftrace_ops(struct ftrace_ops __rcu > **list, > lockdep_is_held(&ftrace_lock)) == ops && > rcu_dereference_protected(ops->next, > lockdep_is_held(&ftrace_lock)) == &ftrace_list_end) { > - *list = &ftrace_list_end; > + rcu_assign_pointer(*list, &ftrace_list_end); > return 0; > } > > @@ -293,7 +293,7 @@ static int remove_ftrace_ops(struct ftrace_ops __rcu > **list, > if (*p != ops) > return -1; > > - *p = (*p)->next; > + rcu_assign_pointer(*p, (*p)->next); > return 0; > } >
