On Wed, 8 Feb 2023 21:33:43 -0500
Steven Rostedt <rostedt@xxxxxxxxxxx> wrote:
> OK, so it doesn't break perf, trace-cmd and rasdaemon, because the enum is
> only needed in the print_fmt part. It can handle it in the field portion.
>
> That is:
>
>
> system: sched
> name: sched_switch
> ID: 285
> 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:char prev_comm[TASK_COMM_LEN]; offset:8; size:16; signed:0;
> ^^^^^^^^^^^^^^ ^^
> is ignored is used
>
>
> field:pid_t prev_pid; offset:24; size:4; signed:1;
> field:int prev_prio; offset:28; size:4; signed:1;
> field:long prev_state; offset:32; size:8; signed:1;
> field:char next_comm[TASK_COMM_LEN]; offset:40; size:16; signed:0;
> field:pid_t next_pid; offset:56; size:4; signed:1;
> field:int next_prio; offset:60; size:4; signed:1;
>
> print fmt: "prev_comm=%s prev_pid=%d prev_prio=%d prev_state=%s%s ==> next_comm=%s next_pid=%d next_prio=%d", REC->prev_comm, REC->prev_pid, REC->prev_prio, (REC->prev_state & ((((0x00000000 | 0x00000001 | 0x00000002 | 0x00000004 | 0x00000008 | 0x00000010 | 0x00000020 | 0x00000040) + 1) << 1) - 1)) ? __print_flags(REC->prev_state & ((((0x00000000 | 0x00000001 | 0x00000002 | 0x00000004 | 0x00000008 | 0x00000010 | 0x00000020 | 0x00000040) + 1) << 1) - 1), "|", { 0x00000001, "S" }, { 0x00000002, "D" }, { 0x00000004, "T" }, { 0x00000008, "t" }, { 0x00000010, "X" }, { 0x00000020, "Z" }, { 0x00000040, "P" }, { 0x00000080, "I" }) : "R", REC->prev_state & (((0x00000000 | 0x00000001 | 0x00000002 | 0x00000004 | 0x00000008 | 0x00000010 | 0x00000020 | 0x00000040) + 1) << 1) ? "+" : "", REC->next_comm, REC->next_pid, REC->next_prio
>
> ^^^^^^^
>
> Is what requires the conversions. So I take that back. It only breaks
> perfetto, and that's because it writes its own parser and doesn't use
> libtraceevent.
Actually, there are cases that this needs to be a number, as b3bc8547d3be6
("tracing: Have TRACE_DEFINE_ENUM affect trace event types as well") made
it update fields as well as the printk fmt.
I think because libtraceevent noticed that it was a "char" array, it just
defaults to "size". But this does have meaning for all other types, and I
can see other parsers requiring that.
-- Steve
