Kernel WARNING at lib/vsprintf.c:2721 while running ftrace kernel selftests

[Sachin Sant]

>> --- interrupt: c00
>> Code: f821ff91 2f890000 409e0034 7c0802a6 3c62fff0 39200001 3d420177 3863e310 992ad6db f8010080 4b209899 60000000 <0fe00000> e8010080 7c0803a6 2f9f0000 
>> ---[ end trace 0000000000000000 ]—
>> 
>> This warning is seen while running test that was added by
>> following commit:
>> 
>> commit 3bf7009251f0f41cdd0188ab7b3879df81810703
>>     tracing/selftests: Add test to test the trace_marker
> 
> This adds the user space selftest that triggered this warning, but it is
> not the cause of it. Could you run this test against kernel builds before
> this commit. Does this test cause this to trigger on older versions of the
> kernel?
> 

Running the mentioned test against an older kernel does not trigger this
warning.

# uname -r
6.7.0
#
#  ./ftracetest test.d/00basic/trace_marker.tc
=== Ftrace unit tests ===
[1] Basic tests on writing to trace_marker [PASS]
[2] (instance)  Basic tests on writing to trace_marker [PASS]


# of passed:  2
# of failed:  0
# of unresolved:  0
# of untested:  0
# of unsupported:  0
# of xfailed:  0
# of undefined(test bug):  0
#

I used this setup to again run bisect between 6.7.0 and 6.8-rc1.
Bisect points to following patch 

commit 8ec90be7f15fac42992ea821be929d3b06cd0fd9
    tracing: Allow for max buffer data size trace_marker writes


— Sachin