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Message-ID: <CANn89iK7Mm4aPpr1-VM5OgicuHrHjo9nm9P9bYgOKKH9yczFzg@mail.gmail.com> Date: Fri, 2 Sep 2022 08:43:07 -0700 From: Eric Dumazet <edumazet@...gle.com> To: Menglong Dong <menglong8.dong@...il.com> Cc: Jakub Kicinski <kuba@...nel.org>, David Miller <davem@...emloft.net>, Paolo Abeni <pabeni@...hat.com>, Steven Rostedt <rostedt@...dmis.org>, Ingo Molnar <mingo@...hat.com>, Menglong Dong <imagedong@...cent.com>, David Ahern <dsahern@...nel.org>, Hao Peng <flyingpeng@...cent.com>, Dongli Zhang <dongli.zhang@...cle.com>, robh@...nel.org, Pavel Begunkov <asml.silence@...il.com>, Luiz Augusto von Dentz <luiz.von.dentz@...el.com>, Vasily Averin <vasily.averin@...ux.dev>, LKML <linux-kernel@...r.kernel.org>, netdev <netdev@...r.kernel.org> Subject: Re: [PATCH net-next v2] net: skb: export skb drop reaons to user by TRACE_DEFINE_ENUM On Fri, Sep 2, 2022 at 7:18 AM <menglong8.dong@...il.com> wrote: > > From: Menglong Dong <imagedong@...cent.com> > > As Eric reported, the 'reason' field is not presented when trace the > kfree_skb event by perf: > > $ perf record -e skb:kfree_skb -a sleep 10 > $ perf script > ip_defrag 14605 [021] 221.614303: skb:kfree_skb: > skbaddr=0xffff9d2851242700 protocol=34525 location=0xffffffffa39346b1 > reason: > > The cause seems to be passing kernel address directly to TP_printk(), > which is not right. As the enum 'skb_drop_reason' is not exported to > user space through TRACE_DEFINE_ENUM(), perf can't get the drop reason > string from the 'reason' field, which is a number. > > Therefore, we introduce the macro DEFINE_DROP_REASON(), which is used > to define the trace enum by TRACE_DEFINE_ENUM(). With the help of > DEFINE_DROP_REASON(), now we can remove the auto-generate that we > introduced in the commit ec43908dd556 > ("net: skb: use auto-generation to convert skb drop reason to string"), > and define the string array 'drop_reasons'. > > Hmmmm...now we come back to the situation that have to maintain drop > reasons in both enum skb_drop_reason and DEFINE_DROP_REASON. But they > are both in dropreason.h, which makes it easier. > > After this commit, now the format of kfree_skb is like this: > > $ cat /tracing/events/skb/kfree_skb/format > name: kfree_skb > ID: 1524 > format: > field:unsigned short common_type; offset:0; size:2; signed:0; > field:unsigned char common_flags; offset:2; size:1; signed:0; > field:unsigned char common_preempt_count; offset:3; size:1; signed:0; > field:int common_pid; offset:4; size:4; signed:1; > > field:void * skbaddr; offset:8; size:8; signed:0; > field:void * location; offset:16; size:8; signed:0; > field:unsigned short protocol; offset:24; size:2; signed:0; > field:enum skb_drop_reason reason; offset:28; size:4; signed:0; > > print fmt: "skbaddr=%p protocol=%u location=%p reason: %s", REC->skbaddr, REC->protocol, REC->location, __print_symbolic(REC->reason, { 1, "NOT_SPECIFIED" }, { 2, "NO_SOCKET" } ...... > > Reported-by: Eric Dumazet <edumazet@...gle.com> Note that I also provided the sha1 of the faulty patch. You should add a corresponding Fixes: tag, to help both humans and bots. This would also hint that this patch should target net tree, not net-next ? > Signed-off-by: Menglong Dong <imagedong@...cent.com> > --- > v2: > - undef FN/FNe after use it (Jakub Kicinski) I would love some feedback from Steven :)
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