linux-kernel - Re: [PATCH] blk-iocost: Fix systemtap error on iocost_ioc_vrate

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Message-ID: <20200421152321.GB5462@mtj.thefacebook.com>
Date:   Tue, 21 Apr 2020 11:23:21 -0400
From:   Tejun Heo <tj@...nel.org>
To:     Waiman Long <longman@...hat.com>
Cc:     Jens Axboe <axboe@...nel.dk>, Steven Rostedt <rostedt@...dmis.org>,
        Ingo Molnar <mingo@...hat.com>,
        Stephen Rothwell <sfr@...b.auug.org.au>,
        linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
        Ming Lei <ming.lei@...hat.com>
Subject: Re: [PATCH] blk-iocost: Fix systemtap error on iocost_ioc_vrate_adj

On Tue, Apr 21, 2020 at 09:07:55AM -0400, Waiman Long wrote:
> Systemtap 4.2 is unable to correctly interpret the "u32 (*missed_ppm)[2]"
> argument of the iocost_ioc_vrate_adj trace entry defined in
> include/trace/events/iocost.h leading to the following error:
> 
>   /tmp/stapAcz0G0/stap_c89c58b83cea1724e26395efa9ed4939_6321_aux_6.c:78:8:
>   error: expected ‘;’, ‘,’ or ‘)’ before ‘*’ token
>    , u32[]* __tracepoint_arg_missed_ppm
> 
> That argument type is indeed rather complex and hard to read. Looking
> at block/blk-iocost.c. It is just a 2-entry u32 array. By simplifying
> the argument to a simple "u32 *missed_ppm" and adjusting the trace
> entry accordingly, the compilation error was gone.
> 
> Fixes: 7caa47151ab2 ("blkcg: implement blk-iocost")
> Signed-off-by: Waiman Long <longman@...hat.com>

Acked-by: Tejun Heo <tj@...nel.org>

Thanks.

-- 
tejun