linux-kernel - Re: [blktrace] c055908abe: WARNING:at_kernel/trace/trace.c:#create_trace_option

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Date:   Sat, 27 Feb 2021 09:49:16 -0500
From:   Steven Rostedt <rostedt@...dmis.org>
To:     kernel test robot <oliver.sang@...el.com>
Cc:     Chaitanya Kulkarni <chaitanya.kulkarni@....com>,
        0day robot <lkp@...el.com>,
        LKML <linux-kernel@...r.kernel.org>, lkp@...ts.01.org,
        axboe@...nel.dk, viro@...iv.linux.org.uk, mingo@...hat.com,
        johannes.thumshirn@....com, damien.lemoal@....com,
        bvanassche@....org, dongli.zhang@...cle.com,
        aravind.ramesh@....com, joshi.k@...sung.com, niklas.cassel@....com,
        hch@....de, osandov@...com, martin.petersen@...cle.com,
        linux-block@...r.kernel.org, linux-fsdevel@...r.kernel.org
Subject: Re: [blktrace]  c055908abe:
 WARNING:at_kernel/trace/trace.c:#create_trace_option_files

On Sat, 27 Feb 2021 19:44:40 +0800
kernel test robot <oliver.sang@...el.com> wrote:

> [   20.216017] WARNING: CPU: 0 PID: 1 at kernel/trace/trace.c:8370 create_trace_option_files (kbuild/src/consumer/kernel/trace/trace.c:8370 (discriminator 1)) 
> [   20.218480] Modules linked in:
> [   20.219395] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.11.0-09341-gc055908abe0d #1
> [   20.221182] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.12.0-1 04/01/2014
> [   20.224540] EIP: create_trace_option_files (kbuild/src/consumer/kernel/trace/trace.c:8370 (discriminator 1)) 
> [ 20.225816] Code: d5 01 83 15 2c b7 08 d5 00 83 c0 01 39 c8 0f 84 c7 00 00 00 8b 14 c7 39 72 44 75 df 83 05 10 b7 08 d5 01 83 15 14 b7 08 d5 00 <0f> 0b 83 05 18 b7 08 d5 01 83 15 1c b7 08 d5 00 83 05 20 b7 08 d5

Looks to be from this:

> +static struct tracer blk_tracer_ext __read_mostly = {
> +	.name		= "blkext",
> +	.init		= blk_tracer_init,
> +	.reset		= blk_tracer_reset,
> +	.start		= blk_tracer_start,
> +	.stop		= blk_tracer_stop,
> +	.print_header	= blk_tracer_print_header,
> +	.print_line	= blk_tracer_print_line_ext,
> +	.flags		= &blk_tracer_flags,

                          ^^^

As blk_tracer already registers those flags, when it gets registered as
a tracer, and flag names can not be duplicated.

I could fix the infrastructure to detect the same set of flags being
registered by two different tracers, but in the mean time, it may still
work to use the blk_trace_flags from blk_tracer, and keep .flags NULL
here.

-- Steve


> +	.set_flag	= blk_tracer_set_flag,
> +};
> +