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author | Tom Zanussi <tom.zanussi@linux.intel.com> | 2018-12-18 14:33:26 -0600 |
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committer | Steven Rostedt (VMware) <rostedt@goodmis.org> | 2018-12-22 08:21:05 -0500 |
commit | 05ddb25cb31491b0901d057c40ad50d01b3db783 (patch) | |
tree | 03a1a4f004d9b848ac7c611ee044c75c83936bba /kernel | |
parent | 912201345f7c39e6b0ac283207be2b6641fa47b9 (diff) | |
download | linux-05ddb25cb31491b0901d057c40ad50d01b3db783.tar.bz2 |
tracing: Add hist trigger comments for variable-related fields
Add a few comments to help clarify how variable and variable reference
fields are used in the code.
Link: http://lkml.kernel.org/r/ea857ce948531d7bec712bbb0f38360aa1d378ec.1545161087.git.tom.zanussi@linux.intel.com
Acked-by: Namhyung Kim <namhyung@kernel.org>
Reviewed-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Diffstat (limited to 'kernel')
-rw-r--r-- | kernel/trace/trace_events_hist.c | 36 |
1 files changed, 36 insertions, 0 deletions
diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c index 1b1aee944588..c5448c103770 100644 --- a/kernel/trace/trace_events_hist.c +++ b/kernel/trace/trace_events_hist.c @@ -40,6 +40,16 @@ enum field_op_id { FIELD_OP_UNARY_MINUS, }; +/* + * A hist_var (histogram variable) contains variable information for + * hist_fields having the HIST_FIELD_FL_VAR or HIST_FIELD_FL_VAR_REF + * flag set. A hist_var has a variable name e.g. ts0, and is + * associated with a given histogram trigger, as specified by + * hist_data. The hist_var idx is the unique index assigned to the + * variable by the hist trigger's tracing_map. The idx is what is + * used to set a variable's value and, by a variable reference, to + * retrieve it. + */ struct hist_var { char *name; struct hist_trigger_data *hist_data; @@ -56,11 +66,29 @@ struct hist_field { const char *type; struct hist_field *operands[HIST_FIELD_OPERANDS_MAX]; struct hist_trigger_data *hist_data; + + /* + * Variable fields contain variable-specific info in var. + */ struct hist_var var; enum field_op_id operator; char *system; char *event_name; + + /* + * The name field is used for EXPR and VAR_REF fields. VAR + * fields contain the variable name in var.name. + */ char *name; + + /* + * When a histogram trigger is hit, if it has any references + * to variables, the values of those variables are collected + * into a var_ref_vals array by resolve_var_refs(). The + * current value of each variable is read from the tracing_map + * using the hist field's hist_var.idx and entered into the + * var_ref_idx entry i.e. var_ref_vals[var_ref_idx]. + */ unsigned int var_ref_idx; bool read_once; }; @@ -365,6 +393,14 @@ struct action_data { union { struct { + /* + * When a histogram trigger is hit, the values of any + * references to variables, including variables being passed + * as parameters to synthetic events, are collected into a + * var_ref_vals array. This var_ref_idx is the index of the + * first param in the array to be passed to the synthetic + * event invocation. + */ unsigned int var_ref_idx; char *match_event; char *match_event_system; |