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Subject: Re: [PATCH v2] bpf: test_bpf: turn of preemption in function
 __run_once
To:     Anders Roxell <anders.roxell@linaro.org>, ast@kernel.org
Cc:     netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
        Arnd Bergmann <arnd@arndb.de>
References: <20190222084652.1326-1-anders.roxell@linaro.org>
From:   Daniel Borkmann <daniel@iogearbox.net>
Message-ID: <31dccc3f-3355-31b6-87c1-81d9ff35515b@iogearbox.net>
Date:   Mon, 25 Feb 2019 22:28:58 +0100
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On 02/22/2019 09:46 AM, Anders Roxell wrote:
> When running BPF test suite the following splat occurs:
> 
> [  415.930950] test_bpf: #0 TAX jited:0
> [  415.931067] BUG: assuming atomic context at lib/test_bpf.c:6674
> [  415.946169] in_atomic(): 0, irqs_disabled(): 0, pid: 11556, name: modprobe
> [  415.953176] INFO: lockdep is turned off.
> [  415.957207] CPU: 1 PID: 11556 Comm: modprobe Tainted: G        W         5.0.0-rc7-next-20190220 #1
> [  415.966328] Hardware name: HiKey Development Board (DT)
> [  415.971592] Call trace:
> [  415.974069]  dump_backtrace+0x0/0x160
> [  415.977761]  show_stack+0x24/0x30
> [  415.981104]  dump_stack+0xc8/0x114
> [  415.984534]  __cant_sleep+0xf0/0x108
> [  415.988145]  test_bpf_init+0x5e0/0x1000 [test_bpf]
> [  415.992971]  do_one_initcall+0x90/0x428
> [  415.996837]  do_init_module+0x60/0x1e4
> [  416.000614]  load_module+0x1de0/0x1f50
> [  416.004391]  __se_sys_finit_module+0xc8/0xe0
> [  416.008691]  __arm64_sys_finit_module+0x24/0x30
> [  416.013255]  el0_svc_common+0x78/0x130
> [  416.017031]  el0_svc_handler+0x38/0x78
> [  416.020806]  el0_svc+0x8/0xc
> 
> Rework so that preemption is disabled when we loop over function
> 'BPF_PROG_RUN(...)'.
> Commit 568f196756ad ("bpf: check that BPF programs run with preemption disabled")
> highlighted the issue.

(Technically not an issue in the test suite itself, but good to have same
 guarantees everywhere in BPF_PROG_RUN().)

> Suggested-by: Arnd Bergmann <arnd@arndb.de>
> Signed-off-by: Anders Roxell <anders.roxell@linaro.org>

Applied, thanks!