STRUCT TRACER(9)

🌸 NAME 🌸

struct tracer — it's the blueprint for one specific tracer, like, all the callbacks it uses to vibe with tracefs 🫶

✨ SYNOPSIS ✨

okay bestie, here's the whole struct, no notes, copy it exactly:

struct tracer {
    const char              *name;
    int (*init)(struct trace_array *tr);
    void (*reset)(struct trace_array *tr);
    void (*start)(struct trace_array *tr);
    void (*stop)(struct trace_array *tr);
    int (*update_thresh)(struct trace_array *tr);
    void (*open)(struct trace_iterator *iter);
    void (*pipe_open)(struct trace_iterator *iter);
    void (*close)(struct trace_iterator *iter);
    void (*pipe_close)(struct trace_iterator *iter);
    ssize_t (*read)(struct trace_iterator *iter, struct file *filp, char
__user *ubuf, size_t cnt, loff_t *ppos);
    ssize_t (*splice_read)(struct trace_iterator *iter, struct file
*filp, loff_t *ppos, struct pipe_inode_info *pipe, size_t len, unsigned
int flags);
  #ifdef CONFIG_FTRACE_STARTUP_TEST;
    int (*selftest)(struct tracer *trace, struct trace_array *tr);
  #endif;
    void (*print_header)(struct seq_file *m);
    enum print_line_t       (*print_line)(struct trace_iterator *iter);
    int (*set_flag)(struct trace_array *tr, u32 old_flags, u32 bit, int
set);
    int (*flag_changed)(struct trace_array *tr, u64 mask, int set);
    struct tracer           *next;
    struct tracer_flags     *flags;
    struct tracer_flags     *default_flags;
    int enabled;
    bool print_max;
    bool allow_instances;
  #ifdef CONFIG_TRACER_MAX_TRACE;
    bool use_max_tr;
  #endif;
    bool noboot;
 };

👑 Members

okay so here's the cast of characters, each one doing its little job 💅

• name — the name you chose for it, the one that shows up so you can select it from the available_tracers file
• init — gets called when you switch over to this tracer (echo name > current_tracer)
• reset — gets called when you switch to some other tracer, byee 👋
• start — gets called when tracing gets unpaused (echo 1 > tracing_on)
• stop — gets called when tracing gets paused (echo 0 > tracing_on)
• update_thresh — gets called whenever tracing_thresh gets updated
• open — gets called when the trace file is opened
• pipe_open — gets called when the trace_pipe file is opened
• close — gets called when the trace file is released
• pipe_close — gets called when the trace_pipe file is released
• read — overrides the default read callback on trace_pipe
• splice_read — overrides the default splice_read callback on trace_pipe
• selftest — the selftest that runs on boot (see trace_selftest.c)
• print_line — the callback that prints a trace, literally its whole moment ✨
• set_flag — signals that one of your private flags changed (the trace_options file)
• flags — your private flags, your lil collection 🎀

🌈 SEE ALSO 🌈

Kernel file ./kernel/trace/trace.h struct cond_snapshot(9), tracer_tracing_is_on_cpu(9), event_trigger_unlock_commit(9), struct event_command(9), enum event_command_flags(9) — go read those next, iykyk 🔥

ngl that's the whole page, bestie. go forth and tracer 💖

mwah, this one's from ./kernel/trace, dated October 2026, and it's struct tracer(9) — slay, periodt 👑