This is a note to let you know that I've just added the patch titled
tracing / synthetic: Disable events after testing in synth_event_gen_test_init()
to the 6.6-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
tracing-synthetic-disable-events-after-testing-in-synth_event_gen_test_init.patch
and it can be found in the queue-6.6 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 88b30c7f5d27e1594d70dc2bd7199b18f2b57fa9 Mon Sep 17 00:00:00 2001
From: "Steven Rostedt (Google)" <rostedt@xxxxxxxxxxx>
Date: Wed, 20 Dec 2023 11:15:25 -0500
Subject: tracing / synthetic: Disable events after testing in synth_event_gen_test_init()
From: Steven Rostedt (Google) <rostedt@xxxxxxxxxxx>
commit 88b30c7f5d27e1594d70dc2bd7199b18f2b57fa9 upstream.
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.
Link: https://lore.kernel.org/linux-trace-kernel/20231220111525.2f0f49b0@xxxxxxxxxxxxxxxxxx
Cc: stable@xxxxxxxxxxxxxxx
Cc: Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxxxx>
Cc: Tom Zanussi <zanussi@xxxxxxxxxx>
Fixes: 9fe41efaca084 ("tracing: Add synth event generation test module")
Acked-by: Masami Hiramatsu (Google) <mhiramat@xxxxxxxxxx>
Reported-by: Alexander Graf <graf@xxxxxxxxxx>
Tested-by: Alexander Graf <graf@xxxxxxxxxx>
Signed-off-by: Steven Rostedt (Google) <rostedt@xxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
kernel/trace/synth_event_gen_test.c | 11 +++++++++++
1 file changed, 11 insertions(+)
--- a/kernel/trace/synth_event_gen_test.c
+++ b/kernel/trace/synth_event_gen_test.c
@@ -477,6 +477,17 @@ static int __init synth_event_gen_test_i
ret = test_trace_synth_event();
WARN_ON(ret);
+
+ /* Disable when done */
+ trace_array_set_clr_event(gen_synth_test->tr,
+ "synthetic",
+ "gen_synth_test", false);
+ trace_array_set_clr_event(empty_synth_test->tr,
+ "synthetic",
+ "empty_synth_test", false);
+ trace_array_set_clr_event(create_synth_test->tr,
+ "synthetic",
+ "create_synth_test", false);
out:
return ret;
}
Patches currently in stable-queue which might be from rostedt@xxxxxxxxxxx are
queue-6.6/ring-buffer-fix-32-bit-rb_time_read-race-with-rb_tim.patch
queue-6.6/ring-buffer-fix-slowpath-of-interrupted-event.patch
queue-6.6/ring-buffer-remove-useless-update-to-write_stamp-in-.patch
queue-6.6/tracing-synthetic-disable-events-after-testing-in-synth_event_gen_test_init.patch
