Message-ID: <e2655687-38ba-4e5b-9573-32eb12fb0583@amazon.com>
Date: Thu, 21 Dec 2023 11:06:38 +0100
From: Alexander Graf <graf@...zon.com>
To: Steven Rostedt <rostedt@...dmis.org>, LKML <linux-kernel@...r.kernel.org>,
	Linux Trace Kernel <linux-trace-kernel@...r.kernel.org>
CC: Masami Hiramatsu <mhiramat@...nel.org>, Mathieu Desnoyers
	<mathieu.desnoyers@...icios.com>, Tom Zanussi <zanussi@...nel.org>
Subject: Re: [PATCH] tracing / synthetic: Disable events after testing in
 synth_event_gen_test_init()

Hi Steve,

On 20.12.23 17:15, Steven Rostedt wrote:
>
> From: "Steven Rostedt (Google)" <rostedt@...dmis.org>
>
> The synth_event_gen_test module can be built in, if someone wants to run
> the tests at boot up and not have to load them.
>
> The synth_event_gen_test_init() function creates and enables the synthetic
> events and runs its tests.
>
> The synth_event_gen_test_exit() disables the events it created and
> destroys the events.
>
> If the module is builtin, the events are never disabled. The issue is, the
> events should be disable after the tests are run. This could be an issue
> if the rest of the boot up tests are enabled, as they expect the events to
> be in a known state before testing. That known state happens to be
> disabled.
>
> When CONFIG_SYNTH_EVENT_GEN_TEST=y and CONFIG_EVENT_TRACE_STARTUP_TEST=y
> a warning will trigger:
>
>   Running tests on trace events:
>   Testing event create_synth_test:
>   Enabled event during self test!
>   ------------[ cut here ]------------
>   WARNING: CPU: 2 PID: 1 at kernel/trace/trace_events.c:4150 event_trace_self_tests+0x1c2/0x480
>   Modules linked in:
>   CPU: 2 PID: 1 Comm: swapper/0 Not tainted 6.7.0-rc2-test-00031-gb803d7c664d5-dirty #276
>   Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
>   RIP: 0010:event_trace_self_tests+0x1c2/0x480
>   Code: bb e8 a2 ab 5d fc 48 8d 7b 48 e8 f9 3d 99 fc 48 8b 73 48 40 f6 c6 01 0f 84 d6 fe ff ff 48 c7 c7 20 b6 ad bb e8 7f ab 5d fc 90 <0f> 0b 90 48 89 df e8 d3 3d 99 fc 48 8b 1b 4c 39 f3 0f 85 2c ff ff
>   RSP: 0000:ffffc9000001fdc0 EFLAGS: 00010246
>   RAX: 0000000000000029 RBX: ffff88810399ca80 RCX: 0000000000000000
>   RDX: 0000000000000000 RSI: ffffffffb9f19478 RDI: ffff88823c734e64
>   RBP: ffff88810399f300 R08: 0000000000000000 R09: fffffbfff79eb32a
>   R10: ffffffffbcf59957 R11: 0000000000000001 R12: ffff888104068090
>   R13: ffffffffbc89f0a0 R14: ffffffffbc8a0f08 R15: 0000000000000078
>   FS:  0000000000000000(0000) GS:ffff88823c700000(0000) knlGS:0000000000000000
>   CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>   CR2: 0000000000000000 CR3: 00000001f6282001 CR4: 0000000000170ef0
>   Call Trace:
>    <TASK>
>    ? __warn+0xa5/0x200
>    ? event_trace_self_tests+0x1c2/0x480
>    ? report_bug+0x1f6/0x220
>    ? handle_bug+0x6f/0x90
>    ? exc_invalid_op+0x17/0x50
>    ? asm_exc_invalid_op+0x1a/0x20
>    ? tracer_preempt_on+0x78/0x1c0
>    ? event_trace_self_tests+0x1c2/0x480
>    ? __pfx_event_trace_self_tests_init+0x10/0x10
>    event_trace_self_tests_init+0x27/0xe0
>    do_one_initcall+0xd6/0x3c0
>    ? __pfx_do_one_initcall+0x10/0x10
>    ? kasan_set_track+0x25/0x30
>    ? rcu_is_watching+0x38/0x60
>    kernel_init_freeable+0x324/0x450
>    ? __pfx_kernel_init+0x10/0x10
>    kernel_init+0x1f/0x1e0
>    ? _raw_spin_unlock_irq+0x33/0x50
>    ret_from_fork+0x34/0x60
>    ? __pfx_kernel_init+0x10/0x10
>    ret_from_fork_asm+0x1b/0x30
>    </TASK>
>
> This is because the synth_event_gen_test_init() left the synthetic events
> that it created enabled. By having it disable them after testing, the
> other selftests will run fine.
>
> Cc: stable@...r.kernel.org
> Fixes: 9fe41efaca084 ("tracing: Add synth event generation test module")
> Reported-by: Alexander Graf <graf@...zon.com>
> Signed-off-by: Steven Rostedt (Google) <rostedt@...dmis.org>


Thanks a bunch for the super quick turnaround time for the fix! I can 
confirm that I'm no longer seeing the warning :)

Tested-by: Alexander Graf <graf@...zon.com>


Do we need another similar patch for the kprobe self tests? The below is 
with 55cb5f43689d7 plus an unrelated initrd patch plus this patch and 
the following .config: http://csgraf.de/tmp2/config-ftrace.xz

[  919.717134] Testing all events: OK
[  924.418194] Testing ftrace filter: OK
[  924.418887] trace_kprobe: Testing kprobe tracing:
[  924.424244] ------------[ cut here ]------------
[  924.424952] WARNING: CPU: 2 PID: 1 at 
kernel/trace/trace_kprobe.c:2073 kprobe_trace_self_tests_init+0x192/0x540
[  924.425659] Modules linked in:
[  924.425886] CPU: 2 PID: 1 Comm: swapper/0 Not tainted 
6.7.0-rc6-00024-gc10698ad3c9a #298
[  924.426448] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 
rel-1.16.2-0-gea1b7a073390-prebuilt.qemu.org 04/01/2014
[  924.427230] RIP: 0010:kprobe_trace_self_tests_init+0x192/0x540
[  924.427639] Code: 7e 10 74 3b 48 8b 36 48 39 d6 75 f2 0f 0b 48 c7 c7 
58 71 79 a5 e8 ee 3e 5a fe 48 c7 c7 20 38 b7 a5 e8 a2 51 68 fe 85 c0 74 
33 <0f> 0b 48 c7 c7 38 73 79 a5 e8 d0 3e 5a fe e8 4b 64 62 fe eb 23 48
[  924.428922] RSP: 0000:ffffab508001be58 EFLAGS: 00010286
[  924.429288] RAX: 00000000fffffff0 RBX: 000000000000005a RCX: 
0000000000000202
[  924.429800] RDX: 0000000000000000 RSI: 000000000002e970 RDI: 
ffffffffa5b708a0
[  924.430295] RBP: 0000000000000000 R08: 0000000000000001 R09: 
ffffffffa4855a90
[  924.430794] R10: 0000000000000007 R11: 000000000000028a R12: 
0000000000000001
[  924.431286] R13: ffffffffa5cc9a00 R14: ffff8cec81bebe00 R15: 
ffffffffa619f0f0
[  924.431785] FS:  0000000000000000(0000) GS:ffff8cecf9100000(0000) 
knlGS:0000000000000000
[  924.432346] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[  924.432748] CR2: 0000000000000000 CR3: 000000004883e001 CR4: 
00000000003706f0
[  924.433246] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 
0000000000000000
[  924.433739] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 
0000000000000400
[  924.434233] Call Trace:
[  924.434418]  <TASK>
[  924.434569]  ? __warn+0x7d/0x140
[  924.434807]  ? kprobe_trace_self_tests_init+0x192/0x540
[  924.435172]  ? report_bug+0xf8/0x1e0
[  924.435430]  ? handle_bug+0x3f/0x70
[  924.435677]  ? exc_invalid_op+0x13/0x60
[  924.435954]  ? asm_exc_invalid_op+0x16/0x20
[  924.436249]  ? rdinit_setup+0x40/0x40
[  924.436509]  ? trace_kprobe_release+0x70/0xb0
[  924.436822]  ? kprobe_trace_self_tests_init+0x192/0x540
[  924.437189]  ? kprobe_trace_self_tests_init+0x421/0x540
[  924.437551]  ? init_kprobe_trace+0x1b0/0x1b0
[  924.437855]  do_one_initcall+0x44/0x200
[  924.438131]  kernel_init_freeable+0x1e8/0x330
[  924.438439]  ? rest_init+0xd0/0xd0
[  924.438682]  kernel_init+0x16/0x130
[  924.438943]  ret_from_fork+0x30/0x50
[  924.439202]  ? rest_init+0xd0/0xd0
[  924.439445]  ret_from_fork_asm+0x11/0x20
[  924.439734]  </TASK>
[  924.439893] ---[ end trace 0000000000000000 ]---
[  924.440217] trace_kprobe: error on cleaning up probes.
[  924.440575] NG: Some tests are failed. Please check them.


Alex




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