From: Alexei Starovoitov <alexei.starovoitov@gmail.com>
To: Daniel Colascione <dancol@google.com>
Cc: Daniel Borkmann <daniel@iogearbox.net>,
Jakub Kicinski <jakub.kicinski@netronome.com>,
Joel Fernandes <joelaf@google.com>,
linux-kernel <linux-kernel@vger.kernel.org>,
Tim Murray <timmurray@google.com>,
netdev <netdev@vger.kernel.org>,
Lorenzo Colitti <lorenzo@google.com>,
Chenbo Feng <fengc@google.com>,
Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
Alexei Starovoitov <ast@fb.com>
Subject: Re: [PATCH v3] Add BPF_SYNCHRONIZE_MAP_TO_MAP_REFERENCES bpf(2) command
Date: Wed, 15 Aug 2018 21:01:47 -0700 [thread overview]
Message-ID: <20180816040145.gqzqicab4s6kcbye@ast-mbp.dhcp.thefacebook.com> (raw)
In-Reply-To: <CAKOZueuACjK0W4byW7omPvEJ-H-8MK1OU3ORrAfNtsEi8NxoPQ@mail.gmail.com>
On Tue, Aug 14, 2018 at 01:37:12PM -0700, Daniel Colascione wrote:
>
> > If we agree on that, should bpf_map_update handle it then?
> > Wouldn't it be much easier to understand and use from user pov?
> > No new commands to learn. map_update syscall replaced the map
> > and old map is no longer accessed by the program via this given map-in-map.
>
> Maybe with a new BPF_SYNCHRONIZE flag for BPF_MAP_UPDATE_ELEM and
> BPF_MAP_DELETE_ELEM. Otherwise, it seems wrong to make every user of
> these commands pay for synchronization that only a few will need.
I don't think extra flag is needed. Extra sync_rcu() for map-in-map
is useful for all users. I would consider it a bugfix,
since users that examine deleted map have this race today
and removing the race is always a good thing especially since the cost
is small.
next prev parent reply other threads:[~2018-08-16 4:01 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <CAKOZuesQ6GdNTGDFsNi4o8LYzxLBtYZ=Cz4=aZbqqCNia+QFnQ@mail.gmail.com>
2018-07-29 20:58 ` [PATCH v3] Add BPF_SYNCHRONIZE_MAP_TO_MAP_REFERENCES bpf(2) command Daniel Colascione
2018-07-30 10:04 ` Daniel Borkmann
2018-07-30 10:25 ` Daniel Colascione
2018-07-31 0:26 ` Jakub Kicinski
2018-07-31 0:33 ` Daniel Colascione
2018-07-31 0:45 ` Jakub Kicinski
2018-07-31 0:50 ` Daniel Colascione
2018-07-31 1:14 ` Jakub Kicinski
2018-07-31 8:34 ` Daniel Borkmann
2018-07-31 9:36 ` Daniel Colascione
2018-08-10 22:52 ` Alexei Starovoitov
2018-08-14 20:37 ` Daniel Colascione
2018-08-16 4:01 ` Alexei Starovoitov [this message]
2018-10-12 10:54 ` [PATCH v4] Wait for running BPF programs when updating map-in-map Daniel Colascione
2018-10-12 20:54 ` Joel Fernandes
2018-10-13 2:31 ` Alexei Starovoitov
2018-10-16 17:39 ` Joel Fernandes
2018-10-18 15:46 ` Alexei Starovoitov
2018-10-18 23:36 ` Joel Fernandes
2018-11-10 2:01 ` Chenbo Feng
2018-11-10 15:22 ` Greg KH
2018-11-10 18:58 ` Chenbo Feng
[not found] ` <CAKOZues6SE_c=ix7ap6QaJHqd1TmYpWWMJiu3=TtuqgKuqOUCA@mail.gmail.com>
2018-08-10 22:29 ` [PATCH v3] Add BPF_SYNCHRONIZE_MAP_TO_MAP_REFERENCES bpf(2) command Alexei Starovoitov
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