diff mbox series

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

Message ID 20200930002011.521337-1-songliubraving@fb.com (mailing list archive)
State Accepted
Headers show
Series [v2,bpf-next] bpf: fix raw_tp test run in preempt kernel | expand

Commit Message

Song Liu Sept. 30, 2020, 12:20 a.m. UTC 
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)
---
 net/bpf/test_run.c | 19 ++++++++-----------
 1 file changed, 8 insertions(+), 11 deletions(-)

Comments

Alexei Starovoitov Sept. 30, 2020, 3:23 a.m. UTC | #1 
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?
Song Liu Sept. 30, 2020, 6:45 a.m. UTC | #2 
> 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
Alexei Starovoitov Sept. 30, 2020, 3:35 p.m. UTC | #3 
On 9/29/20 11:45 PM, Song Liu wrote:
> 
> 
>> 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

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
Song Liu Sept. 30, 2020, 3:48 p.m. UTC | #4 
> On Sep 30, 2020, at 8:35 AM, Alexei Starovoitov <ast@fb.com> wrote:
> 
> On 9/29/20 11:45 PM, Song Liu wrote:
>>> 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
> 
> could you try without -b ?

Yes! -b is the problem here. 

I think the right way to format-patch is to use --ignore-space-at-eol 
instead of -b. 

Thanks,
Song
diff mbox series

Patch

diff --git a/net/bpf/test_run.c b/net/bpf/test_run.c
index fde5db93507c4..c1c30a9f76f34 100644
--- a/net/bpf/test_run.c
+++ b/net/bpf/test_run.c
@@ -252,9 +252,7 @@  __bpf_prog_test_run_raw_tp(void *data)
 	struct bpf_raw_tp_test_run_info *info = data;
 
 	rcu_read_lock();
-	migrate_disable();
 	info->retval = BPF_PROG_RUN(info->prog, info->ctx);
-	migrate_enable();
 	rcu_read_unlock();
 }
 
@@ -266,6 +264,7 @@  int bpf_prog_test_run_raw_tp(struct bpf_prog *prog,
 	__u32 ctx_size_in = kattr->test.ctx_size_in;
 	struct bpf_raw_tp_test_run_info info;
 	int cpu = kattr->test.cpu, err = 0;
+	int current_cpu;
 
 	/* doesn't support data_in/out, ctx_out, duration, or repeat */
 	if (kattr->test.data_in || kattr->test.data_out ||
@@ -293,27 +292,25 @@  int bpf_prog_test_run_raw_tp(struct bpf_prog *prog,
 
 	info.prog = prog;
 
+	current_cpu = get_cpu();
 	if ((kattr->test.flags & BPF_F_TEST_RUN_ON_CPU) == 0 ||
-	    cpu == smp_processor_id()) {
+	    cpu == current_cpu) {
 		__bpf_prog_test_run_raw_tp(&info);
-	} else {
+	} else if (cpu >= nr_cpu_ids || !cpu_online(cpu)) {
 		/* smp_call_function_single() also checks cpu_online()
 		 * after csd_lock(). However, since cpu is from user
 		 * space, let's do an extra quick check to filter out
 		 * invalid value before smp_call_function_single().
 		 */
-		if (cpu >= nr_cpu_ids || !cpu_online(cpu)) {
 		err = -ENXIO;
-			goto out;
-		}
-
+	} else {
 		err = smp_call_function_single(cpu, __bpf_prog_test_run_raw_tp,
 					       &info, 1);
-		if (err)
-			goto out;
 	}
+	put_cpu();
 
-	if (copy_to_user(&uattr->test.retval, &info.retval, sizeof(u32)))
+	if (!err &&
+	    copy_to_user(&uattr->test.retval, &info.retval, sizeof(u32)))
 		err = -EFAULT;
 
 out: