netdev - Re: [PATCH v2 bpf-next] bpf: fix raw

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Date:   Wed, 30 Sep 2020 08:35:54 -0700
From:   Alexei Starovoitov <ast@...com>
To:     Song Liu <songliubraving@...com>,
        Alexei Starovoitov <alexei.starovoitov@...il.com>
CC:     Network Development <netdev@...r.kernel.org>,
        bpf <bpf@...r.kernel.org>, Kernel Team <Kernel-team@...com>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...omium.org>
Subject: Re: [PATCH v2 bpf-next] bpf: fix raw_tp test run in preempt kernel

On 9/29/20 11:45 PM, Song Liu wrote:
> 
> 
>> On Sep 29, 2020, at 8:23 PM, Alexei Starovoitov <alexei.starovoitov@...il.com> wrote:
>>
>> On Tue, Sep 29, 2020 at 5:20 PM Song Liu <songliubraving@...com> wrote:
>>>
>>> In preempt kernel, BPF_PROG_TEST_RUN on raw_tp triggers:
>>>
>>> [   35.874974] BUG: using smp_processor_id() in preemptible [00000000]
>>> code: new_name/87
>>> [   35.893983] caller is bpf_prog_test_run_raw_tp+0xd4/0x1b0
>>> [   35.900124] CPU: 1 PID: 87 Comm: new_name Not tainted 5.9.0-rc6-g615bd02bf #1
>>> [   35.907358] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996),
>>> BIOS 1.10.2-1ubuntu1 04/01/2014
>>> [   35.916941] Call Trace:
>>> [   35.919660]  dump_stack+0x77/0x9b
>>> [   35.923273]  check_preemption_disabled+0xb4/0xc0
>>> [   35.928376]  bpf_prog_test_run_raw_tp+0xd4/0x1b0
>>> [   35.933872]  ? selinux_bpf+0xd/0x70
>>> [   35.937532]  __do_sys_bpf+0x6bb/0x21e0
>>> [   35.941570]  ? find_held_lock+0x2d/0x90
>>> [   35.945687]  ? vfs_write+0x150/0x220
>>> [   35.949586]  do_syscall_64+0x2d/0x40
>>> [   35.953443]  entry_SYSCALL_64_after_hwframe+0x44/0xa9
>>>
>>> Fix this by calling migrate_disable() before smp_processor_id().
>>>
>>> Fixes: 1b4d60ec162f ("bpf: Enable BPF_PROG_TEST_RUN for raw_tracepoint")
>>> Reported-by: Alexei Starovoitov <ast@...nel.org>
>>> Signed-off-by: Song Liu <songliubraving@...com>
>>>
>>> ---
>>> Changes v1 => v2:
>>> 1. Keep rcu_read_lock/unlock() in original places. (Alexei)
>>> 2. Use get_cpu() instead of smp_processor_id(). (Alexei)
>>
>> Applying: bpf: fix raw_tp test run in preempt kernel
>> Using index info to reconstruct a base tree...
>> error: patch failed: net/bpf/test_run.c:293
>> error: net/bpf/test_run.c: patch does not apply
>> error: Did you hand edit your patch?
> 
> This is so weird. I cannot apply it myself. :(
> 
> [localhost] g co -b bpf-next-temp
> Switched to a new branch 'bpf-next-temp'
> 
> [localhost] g format-patch -b HEAD~1 --subject-prefix "PATCH v3 bpf-next"
> 0001-bpf-fix-raw_tp-test-run-in-preempt-kernel.patch

could you try without -b ?

> [localhost] g reset --hard HEAD~1
> HEAD is now at b0efc216f5779 libbpf: Compile in PIC mode only for shared library case
> 
> [localhost] g am 0001-bpf-fix-raw_tp-test-run-in-preempt-kernel.patch
> Applying: bpf: fix raw_tp test run in preempt kernel
> error: patch failed: net/bpf/test_run.c:293
> error: net/bpf/test_run.c: patch does not apply
> Patch failed at 0001 bpf: fix raw_tp test run in preempt kernel
> hint: Use 'git am --show-current-patch' to see the failed patch
> When you have resolved this problem, run "git am --continue".
> If you prefer to skip this patch, run "git am --skip" instead.
> To restore the original branch and stop patching, run "git am --abort".

very odd indeed.

> Any hint on how to fix this? Alternatively, could you please pull the
> change from
> 
>     https://git.kernel.org/pub/scm/linux/kernel/git/song/linux.git  raw_tp_preempt_fix

pulled. thanks