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Message-ID: <CAADnVQJvzYn3Yw4-exrvUUTFijq0yEJruLkxfzutEgJUVtUj3g@mail.gmail.com> Date: Wed, 30 Mar 2022 08:09:59 -0700 From: Alexei Starovoitov <alexei.starovoitov@...il.com> To: Masami Hiramatsu <mhiramat@...nel.org> Cc: Jakub Kicinski <kuba@...nel.org>, "David S. Miller" <davem@...emloft.net>, Daniel Borkmann <daniel@...earbox.net>, Peter Zijlstra <peterz@...radead.org>, Andrii Nakryiko <andrii@...nel.org>, Network Development <netdev@...r.kernel.org>, bpf <bpf@...r.kernel.org>, Kernel Team <kernel-team@...com> Subject: Re: pull-request: bpf 2022-03-29 On Wed, Mar 30, 2022 at 2:15 AM Masami Hiramatsu <mhiramat@...nel.org> wrote: > > On Wed, 30 Mar 2022 13:52:17 +0900 > Masami Hiramatsu <mhiramat@...nel.org> wrote: > > > On Tue, 29 Mar 2022 18:51:22 -0700 > > Alexei Starovoitov <alexei.starovoitov@...il.com> wrote: > > > > > On Tue, Mar 29, 2022 at 6:41 PM Jakub Kicinski <kuba@...nel.org> wrote: > > > > > > > > On Tue, 29 Mar 2022 16:49:24 -0700 Alexei Starovoitov wrote: > > > > > Hi David, hi Jakub, > > > > > > > > > > The following pull-request contains BPF updates for your *net* tree. > > > > > > > > > > We've added 16 non-merge commits during the last 1 day(s) which contain > > > > > a total of 24 files changed, 354 insertions(+), 187 deletions(-). > > > > > > > > > > The main changes are: > > > > > > > > > > 1) x86 specific bits of fprobe/rethook, from Masami and Peter. > > > > > > > > > > 2) ice/xsk fixes, from Maciej and Magnus. > > > > > > > > > > 3) Various small fixes, from Andrii, Yonghong, Geliang and others. > > > > > > > > There are some new sparse warnings here that look semi-legit. > > > > As in harmless but not erroneous. > > > > > > Both are new warnings and not due to these patches, right? > > > > > > > kernel/trace/rethook.c:68:9: error: incompatible types in comparison expression (different address spaces): > > > > kernel/trace/rethook.c:68:9: void ( [noderef] __rcu * )( ... ) > > > > kernel/trace/rethook.c:68:9: void ( * )( ... ) > > > > > > > > 66 void rethook_free(struct rethook *rh) > > > > 67 { > > > > 68 rcu_assign_pointer(rh->handler, NULL); > > > > 69 > > > > 70 call_rcu(&rh->rcu, rethook_free_rcu); > > > > 71 } > > > > > > > > Looks like this should be a WRITE_ONCE() ? > > > > > > Masami, please take a look. > > > > Yeah, I think we should make this rcu pointer (and read side must use rcu_dereference()) > > because this rh->handler becomes the key to disable this rethook. > > Let me fix that. > > Sorry, please ignore this. Since the handler pointed by rh->handler never > be removed (unless removed by modules, but this will not happen while > the rethook is running), YES, WRITE_ONCE() is enough. > Please add below. > > From 92c9c784458f03900823360981812220ce3c7bf3 Mon Sep 17 00:00:00 2001 > From: Masami Hiramatsu <mhiramat@...nel.org> > Date: Wed, 30 Mar 2022 18:13:42 +0900 > Subject: [PATCH] rethook: Fix to use WRITE_ONCE() for rethook::handler > > Since the function pointered by rethook::handler never be removed when > the rethook is alive, it doesn't need to use rcu_assign_pointer() to > update it. Just use WRITE_ONCE(). > > Reported-by: Alexei Starovoitov <alexei.starovoitov@...il.com> > Signed-off-by: Masami Hiramatsu <mhiramat@...nel.org> Could you please send it as a proper patch so it registers in patchwork? > --- > kernel/trace/rethook.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/kernel/trace/rethook.c b/kernel/trace/rethook.c > index ab463a4d2b23..b56833700d23 100644 > --- a/kernel/trace/rethook.c > +++ b/kernel/trace/rethook.c > @@ -65,7 +65,7 @@ static void rethook_free_rcu(struct rcu_head *head) > */ > void rethook_free(struct rethook *rh) > { > - rcu_assign_pointer(rh->handler, NULL); > + WRITE_ONCE(rh->handler, NULL); > > call_rcu(&rh->rcu, rethook_free_rcu); > } > -- > 2.25.1 > -- > Masami Hiramatsu <mhiramat@...nel.org>
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