Re: [PATCH v2 bpf-next] bpf: fix raw_tp test run in preempt kernel

From: Song Liu <songliubraving@fb.com>
To: Alexei Starovoitov <alexei.starovoitov@gmail.com>
Cc: Network Development <netdev@vger.kernel.org>,
	bpf <bpf@vger.kernel.org>, Kernel Team <Kernel-team@fb.com>,
	Alexei Starovoitov <ast@kernel.org>,
	"Daniel Borkmann" <daniel@iogearbox.net>,
	John Fastabend <john.fastabend@gmail.com>,
	KP Singh <kpsingh@chromium.org>
Subject: Re: [PATCH v2 bpf-next] bpf: fix raw_tp test run in preempt kernel
Date: Wed, 30 Sep 2020 06:45:40 +0000	[thread overview]
Message-ID: <5684F41E-8748-4CBE-B37F-0E4AADC0A799@fb.com> (raw)
In-Reply-To: <CAADnVQ+jaUfJkD0POaRyrmrLueVP9x-rN8bcN5eEz4XPBk96bw@mail.gmail.com>

> On Sep 29, 2020, at 8:23 PM, Alexei Starovoitov <alexei.starovoitov@gmail.com> wrote:
> 
> On Tue, Sep 29, 2020 at 5:20 PM Song Liu <songliubraving@fb.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@kernel.org>
>> Signed-off-by: Song Liu <songliubraving@fb.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

[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".

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

Thanks,
Song