Messages in this thread | | | Date | Mon, 31 Jul 2023 20:58:53 -0700 | From | John Fastabend <> | Subject | Re: [PATCH net] bpf: sockmap: Remove preempt_disable in sock_map_sk_acquire |
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Jakub Sitnicki wrote: > > On Fri, Jul 28, 2023 at 08:44 AM +02, tglozar@redhat.com wrote: > > From: Tomas Glozar <tglozar@redhat.com> > > > > Disabling preemption in sock_map_sk_acquire conflicts with GFP_ATOMIC > > allocation later in sk_psock_init_link on PREEMPT_RT kernels, since > > GFP_ATOMIC might sleep on RT (see bpf: Make BPF and PREEMPT_RT co-exist > > patchset notes for details). > > > > This causes calling bpf_map_update_elem on BPF_MAP_TYPE_SOCKMAP maps to > > BUG (sleeping function called from invalid context) on RT kernels. > > > > preempt_disable was introduced together with lock_sk and rcu_read_lock > > in commit 99ba2b5aba24e ("bpf: sockhash, disallow bpf_tcp_close and update > > in parallel"), probably to match disabled migration of BPF programs, and > > is no longer necessary. > > > > Remove preempt_disable to fix BUG in sock_map_update_common on RT. > > > > Signed-off-by: Tomas Glozar <tglozar@redhat.com> > > --- > > We disable softirq and hold a spin lock when modifying the map/hash in > sock_{map,hash}_update_common so this LGTM: >
Agree.
> Reviewed-by: Jakub Sitnicki <jakub@cloudflare.com>
Reviewed-by: John Fastabend <john.fastabend@gmail.com>
> > You might want some extra tags: > > Link: https://lore.kernel.org/all/20200224140131.461979697@linutronix.de/ > Fixes: 99ba2b5aba24 ("bpf: sockhash, disallow bpf_tcp_close and update in parallel")
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