Re: Duplicate fields in event format of `regcache_sync `

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Sorry Steven I forgot to reply all.
This is the original message:
Perfect,

I can prepare a patch, I think this would be a good learning opportunity for me.


Thank you,

Philippe

On 2020-11-20 1:47 p.m., Steven Rostedt wrote:
On Fri, 20 Nov 2020 12:50:33 -0500
Philippe Duplessis-Guindon <pduplessis@xxxxxxxxxxxx> wrote:

Hi,

I am doing an ftrace plugin for Babeltrace 2 [1], and while I was
parsing the event fields I had an error saying that `regcache_sync` has
2 fields named `type`. The problem seems to come from the
drivers/base/regmap/trace.h file [2]. This is the patch where this was
added: [3]. The `int field` type is not assigned, so I was wondering if
it is normal that the field is there.

This is the format of this event:

$ sudo cat /sys/kernel/debug/tracing/events/regmap/regcache_sync/format
name: regcache_sync
ID: 1216
format:
    field:unsigned short common_type;    offset:0;    size:2;    signed:0;
    field:unsigned char common_flags;    offset:2;    size:1;    signed:0;
    field:unsigned char common_preempt_count; offset:3; size:1;signed:0;
    field:int common_pid;    offset:4;    size:4;    signed:1;

    field:__data_loc char[] name;    offset:8;    size:4;    signed:1;
    field:__data_loc char[] status;    offset:12;    size:4;    signed:1;
    field:__data_loc char[] type;    offset:16;    size:4;    signed:1;
    field:int type;    offset:20;    size:4;    signed:1;

    print fmt: "%s type=%s status=%s", __get_str(name), __get_str(type),
__get_str(status)


It looks like dumb luck that this ever worked. :-/

The correct fix is to nuke that "int type" field. It's not even assigned.

Thanks for pointing this out.

-- Steve


Thank you,

Philippe


[1] https://babeltrace.org/

[2]
https://github.com/torvalds/linux/blob/master/drivers/base/regmap/trace.h#L129

[3]
https://github.com/torvalds/linux/commit/593600890110c02eb471cf844649dee213870416




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