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SubjectRe: Duplicate fields in event format of `regcache_sync `
On Fri, 20 Nov 2020 12:50:33 -0500
Philippe Duplessis-Guindon <pduplessis@efficios.com> 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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