Hello Steven Rostedt,
Commit 5abb6ccb58f0 ("tracing: Have function graph tracer option
sleep-time be per instance") from Nov 14, 2025 (linux-next), leads to
the following Smatch static checker warning:
kernel/trace/trace_functions_graph.c:1649 func_graph_set_flag()
warn: unsigned 'fgraph_no_sleep_time' is never less than zero.
kernel/trace/trace_functions_graph.c:1671 func_graph_set_flag()
warn: unsigned 'fgraph_no_sleep_time' is never less than zero.
kernel/trace/trace_functions_graph.c
1637 static int
1638 func_graph_set_flag(struct trace_array *tr, u32 old_flags, u32 bit,
int set)
1639 {
1640 /*
1641 * The function profiler gets updated even if function graph
1642 * isn't the current tracer. Handle it separately.
1643 */
1644 #ifdef CONFIG_FUNCTION_PROFILER
1645 if (bit == TRACE_GRAPH_SLEEP_TIME && (tr->flags &
TRACE_ARRAY_FL_GLOBAL) &&
1646 !!set == fprofile_no_sleep_time) {
1647 if (set) {
1648 fgraph_no_sleep_time--;
--> 1649 if (WARN_ON_ONCE(fgraph_no_sleep_time < 0))
^^^^^^^^^^^^^^^^^^^^^^^^
Impossible. Unsigned.
1650 fgraph_no_sleep_time = 0;
1651 fprofile_no_sleep_time = false;
1652 } else {
1653 fgraph_no_sleep_time++;
1654 fprofile_no_sleep_time = true;
1655 }
1656 }
1657 #endif
1658
1659 /* Do nothing if the current tracer is not this tracer */
1660 if (tr->current_trace != &graph_trace)
1661 return 0;
1662
1663 /* Do nothing if already set. */
1664 if (!!set == !!(tr->current_trace_flags->val & bit))
1665 return 0;
1666
1667 switch (bit) {
1668 case TRACE_GRAPH_SLEEP_TIME:
1669 if (set) {
1670 fgraph_no_sleep_time--;
1671 if (WARN_ON_ONCE(fgraph_no_sleep_time < 0))
^^^^^^^^^^^^^^^^^^^^^^^^
Same.
1672 fgraph_no_sleep_time = 0;
1673 } else {
1674 fgraph_no_sleep_time++;
1675 }
1676 break;
1677
1678 case TRACE_GRAPH_PRINT_IRQS:
1679 if (set)
1680 ftrace_graph_skip_irqs--;
1681 else
1682 ftrace_graph_skip_irqs++;
1683 if (WARN_ON_ONCE(ftrace_graph_skip_irqs < 0))
1684 ftrace_graph_skip_irqs = 0;
1685 break;
1686
1687 case TRACE_GRAPH_ARGS:
1688 return ftrace_graph_trace_args(tr, set);
1689 }
1690
1691 return 0;
1692 }
regards,
dan carpenter
