On Fri, Sep 22, 2017 at 02:59:55PM -0500, Tom Zanussi wrote:
> Add support for simple addition, subtraction, and unary expressions
> (-(expr) and expr, where expr = b-a, a+b, a+b+c) to hist triggers, in
> order to support a minimal set of useful inter-event calculations.
>
> These operations are needed for calculating latencies between events
> (timestamp1-timestamp0) and for combined latencies (latencies over 3
> or more events).
>
> In the process, factor out some common code from key and value
> parsing.
>
> Signed-off-by: Tom Zanussi <tom.zanussi@xxxxxxxxxxxxxxx>
> ---
[SNIP]
> +static struct hist_field *parse_unary(struct hist_trigger_data *hist_data,
> + struct trace_event_file *file,
> + char *str, unsigned long flags,
> + char *var_name, unsigned int level)
> +{
> + struct hist_field *operand1, *expr = NULL;
> + unsigned long operand_flags;
> + int ret = 0;
> + char *s;
> +
> + // we support only -(xxx) i.e. explicit parens required
> +
> + if (level > 2) {
> + ret = -EINVAL;
> + goto free;
> + }
> +
> + str++; // skip leading '-'
> +
> + s = strchr(str, '(');
> + if (s)
> + str++;
> + else {
> + ret = -EINVAL;
> + goto free;
> + }
> +
> + s = strchr(str, ')');
> + if (s)
> + *s = '\0';
> + else {
> + ret = -EINVAL; // no closing ')'
> + goto free;
> + }
> +
> + strsep(&str, "(");
> + if (!str) {
> + ret = -EINVAL;
> + goto free;
> + }
> +
> + flags |= HIST_FIELD_FL_EXPR;
> + expr = create_hist_field(hist_data, NULL, flags, var_name);
> + if (!expr) {
> + ret = -ENOMEM;
> + goto free;
> + }
> +
> + operand_flags = 0;
> + operand1 = parse_expr(hist_data, file, str, operand_flags, NULL, ++level);
> + if (IS_ERR(operand1)) {
> + ret = PTR_ERR(operand1);
> + goto free;
> + }
> +
> + expr->fn = hist_field_unary_minus;
> + expr->operands[0] = operand1;
> + expr->operator = FIELD_OP_UNARY_MINUS;
> + expr->name = expr_str(expr, 0);
> +
> + return expr;
> + free:
Missing destroy_hist_field(expr, 0)?
Thanks,
Namhyung
> + return ERR_PTR(ret);
> +}
> +
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