On Tue, Sep 01, 2020 at 12:16:17PM +0300, Adrian Hunter wrote: > Add synchronize_rcu() after list_del_rcu() in > ftrace_remove_trampoline_from_kallsyms() to protect readers of > ftrace_ops_trampoline_list (in ftrace_get_trampoline_kallsym) > which is used when kallsyms is read. > > Fixes: fc0ea795f53c8d ("ftrace: Add symbols for ftrace trampolines") > Signed-off-by: Adrian Hunter <adrian.hun...@intel.com> > --- > kernel/trace/ftrace.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c > index 275441254bb5..4e64367c9774 100644 > --- a/kernel/trace/ftrace.c > +++ b/kernel/trace/ftrace.c > @@ -2782,6 +2782,7 @@ static void > ftrace_remove_trampoline_from_kallsyms(struct ftrace_ops *ops) > { > lockdep_assert_held(&ftrace_lock); > list_del_rcu(&ops->list); > + synchronize_rcu(); > }
Hurmph, we've just done a ton of that: ftrace_shutdown() synchronize_rcu_tasks_rude() ftrace_trampoline_free() ftrace_remove_trampoline_from_kallsyms() So would it not be better to move that call before the existing synchronize_rcu_tasks stuff rather than adding another synchronize_rcu() call?