On Wed, Nov 17, 2021 at 10:50:43AM IST, Andrii Nakryiko wrote: > On Mon, Nov 15, 2021 at 11:18 AM Kumar Kartikeya Dwivedi > <memxor@xxxxxxxxx> wrote: > > > > resolve_btfids prints a warning when it finds an unresolved symbol, > > (id == 0) in id_patch. This can be the case for BTF sets that are empty > > (due to disabled config options), hence printing warnings for certain > > builds, most recently seen in [0]. Hence, demote the warning to debug > > log level to avoid build time noise. > > > > [0]: https://lore.kernel.org/all/1b99ae14-abb4-d18f-cc6a-d7e523b25542@xxxxxxxxx > > > > Fixes: 0e32dfc80bae ("bpf: Enable TCP congestion control kfunc from modules") > > Reported-by: Pavel Skripkin <paskripkin@xxxxxxxxx> > > Signed-off-by: Kumar Kartikeya Dwivedi <memxor@xxxxxxxxx> > > --- > > tools/bpf/resolve_btfids/main.c | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/tools/bpf/resolve_btfids/main.c b/tools/bpf/resolve_btfids/main.c > > index a59cb0ee609c..833bfcc9ccf6 100644 > > --- a/tools/bpf/resolve_btfids/main.c > > +++ b/tools/bpf/resolve_btfids/main.c > > @@ -569,7 +569,7 @@ static int id_patch(struct object *obj, struct btf_id *id) > > int i; > > > > if (!id->id) { > > - pr_err("WARN: resolve_btfids: unresolved symbol %s\n", id->name); > > + pr_debug("WARN: resolve_btfids: unresolved symbol %s\n", id->name); > > This is an important warning that helps detect some misconfiguration, > we cannot just hide it. If it really is happening for empty lists > (why?), we should handle empty lists better, but not hide the warning. > +Cc Jiri Sorry for the delay. The 'why' is because in case of empty BTF set, the id->cnt aliasing over id->id (for non-set __BTF_ID_*) is zero, so it trips over when it sees it as 0 for empty set in id_patch. So, what would be your opinion on how to handle this case? Ignore the warning case for empty sets specifically? (e.g. using string comparison in id_patch for id->name, or split id and cnt out of union and assign non-zero to id in case cnt == 0, otherwise copy (saving strncmp for all symbols in id_patch)) Also, if I'm respinning, any comments on the first two which are also fixes for bugs I introduced, so that we can avoid another round? -- Kartikeya
