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From: Hao Luo <haoluo@google.com>
To: Yonghong Song <yhs@fb.com>
Cc: Andrii Nakryiko <andrii@kernel.org>, bpf <bpf@vger.kernel.org>,
	Networking <netdev@vger.kernel.org>,
	Alexei Starovoitov <ast@fb.com>,
	Daniel Borkmann <daniel@iogearbox.net>,
	Kernel Team <kernel-team@fb.com>,
	Alexei Starovoitov <ast@kernel.org>
Subject: Re: [PATCH v2 bpf-next 4/7] selftests/bpf: sync RCU before unloading bpf_testmod
Date: Mon, 11 Jan 2021 10:59:26 -0800	[thread overview]
Message-ID: <CA+khW7jcXf=qLQB1zcV9TQKNKb64onWicmrx3iH8FNj5broahA@mail.gmail.com> (raw)
In-Reply-To: <2e7a9040-6b16-bb9f-0cab-73161899e1f1@fb.com>

Acked-by: Hao Luo <haoluo@google.com>

On Sun, Jan 10, 2021 at 8:05 PM Yonghong Song <yhs@fb.com> wrote:
>
>
>
> On 1/8/21 2:09 PM, Andrii Nakryiko wrote:
> > If some of the subtests use module BTFs through ksyms, they will cause
> > bpf_prog to take a refcount on bpf_testmod module, which will prevent it from
> > successfully unloading. Module's refcnt is decremented when bpf_prog is freed,
> > which generally happens in RCU callback. So we need to trigger
> > syncronize_rcu() in the kernel, which can be achieved nicely with
> > membarrier(MEMBARRIER_CMD_GLOBAL) syscall. So do that in kernel_sync_rcu() and
> > make it available to other test inside the test_progs. This synchronize_rcu()
> > is called before attempting to unload bpf_testmod.
> >
> > Fixes: 9f7fa225894c ("selftests/bpf: Add bpf_testmod kernel module for testing")
> > Suggested-by: Alexei Starovoitov <ast@kernel.org>
> > Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
>
> Acked-by: Yonghong Song <yhs@fb.com>

  reply	other threads:[~2021-01-11 19:00 UTC|newest]

Thread overview: 27+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-01-08 22:09 [PATCH v2 bpf-next 0/7] Support kernel module ksym variables Andrii Nakryiko
2021-01-08 22:09 ` [PATCH v2 bpf-next 1/7] bpf: add bpf_patch_call_args prototype to include/linux/bpf.h Andrii Nakryiko
2021-01-11  4:02   ` Yonghong Song
2021-01-08 22:09 ` [PATCH v2 bpf-next 2/7] bpf: avoid warning when re-casting __bpf_call_base into __bpf_call_base_args Andrii Nakryiko
2021-01-11  4:03   ` Yonghong Song
2021-01-08 22:09 ` [PATCH v2 bpf-next 3/7] bpf: declare __bpf_free_used_maps() unconditionally Andrii Nakryiko
2021-01-11  4:03   ` Yonghong Song
2021-01-08 22:09 ` [PATCH v2 bpf-next 4/7] selftests/bpf: sync RCU before unloading bpf_testmod Andrii Nakryiko
2021-01-11  4:05   ` Yonghong Song
2021-01-11 18:59     ` Hao Luo [this message]
2021-01-08 22:09 ` [PATCH v2 bpf-next 5/7] bpf: support BPF ksym variables in kernel modules Andrii Nakryiko
2021-01-11  4:13   ` Yonghong Song
2021-01-11 21:29     ` Andrii Nakryiko
2021-01-12  1:25       ` Yonghong Song
2021-01-11 18:59   ` Hao Luo
2021-01-11 21:31     ` Andrii Nakryiko
2021-01-08 22:09 ` [PATCH v2 bpf-next 6/7] libbpf: support kernel module ksym externs Andrii Nakryiko
2021-01-11  4:15   ` Yonghong Song
2021-01-11 21:37     ` Andrii Nakryiko
2021-01-12  1:34       ` Yonghong Song
2021-01-12  6:45         ` Andrii Nakryiko
2021-01-11 19:00   ` Hao Luo
2021-01-11 21:39     ` Andrii Nakryiko
2021-01-08 22:09 ` [PATCH v2 bpf-next 7/7] selftests/bpf: test " Andrii Nakryiko
2021-01-11  4:18   ` Yonghong Song
2021-01-11 21:40     ` Andrii Nakryiko
2021-01-11 19:00   ` Hao Luo

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