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tracing: add format file to describe event struct fields

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This patch adds the "format" file to the trace point event directory.
This is based off of work by Tom Zanussi, in which a file is exported
to be tread from user land such that a user space app may read the
binary record stored in the ring buffer.

 # cat /debug/tracing/events/sched/sched_switch/format
        field:pid_t prev_pid;   offset:12;      size:4;
        field:int prev_prio;    offset:16;      size:4;
        field special:char next_comm[TASK_COMM_LEN];    offset:20;      size:16;
        field:pid_t next_pid;   offset:36;      size:4;
        field:int next_prio;    offset:40;      size:4;

Idea-from: Tom Zanussi <tzanussi@gmail.com>
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
This commit is contained in:
Steven Rostedt
2009-03-02 13:53:59 -05:00
parent f9520750c4
commit 981d081ec8
4 changed files with 110 additions and 1 deletions
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kernel/trace/trace.h
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@@ -754,6 +754,7 @@ struct ftrace_event_call {
int (*raw_init)(void);
int (*raw_reg)(void);
void (*raw_unreg)(void);
int (*show_format)(struct trace_seq *s);
};
void event_trace_printk(unsigned long ip, const char *fmt, ...);