tracing/boot: Add ftrace.instance.*.alloc_snapshot option

mhiramat · rostedt · commit c16340971949 · 2020-10-15T12:01:13.000-04:00
Add ftrace.instance.*.alloc_snapshot option. This option has been described in Documentation/trace/boottime-trace.rst but not implemented yet. ftrace.[instance.INSTANCE.]alloc_snapshot Allocate snapshot buffer. The difference from kernel.alloc_snapshot is that the kernel.alloc_snapshot will allocate the buffer only for the main instance, but this can allocate buffer for any new instances. Link: https://lkml.kernel.org/r/160234368948.400560.15313384470765915015.stgit@devnote2 Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org> Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
diff --git a/kernel/trace/trace_boot.c b/kernel/trace/trace_boot.c
@@ -284,6 +284,12 @@ trace_boot_enable_tracer(struct trace_array *tr, struct xbc_node *node)
 		if (tracing_set_tracer(tr, p) < 0)
 			pr_err("Failed to set given tracer: %s\n", p);
 	}
+
+	/* Since tracer can free snapshot buffer, allocate snapshot here.*/
+	if (xbc_node_find_value(node, "alloc_snapshot", NULL)) {
+		if (tracing_alloc_snapshot_instance(tr) < 0)
+			pr_err("Failed to allocate snapshot buffer\n");
+	}
 }
 
 static void __init

Original file line number	Diff line number	Diff line change
`@@ -284,6 +284,12 @@ trace_boot_enable_tracer(struct trace_array tr, struct xbc_node node)`
`284`	`284`	`if (tracing_set_tracer(tr, p) < 0)`
`285`	`285`	`pr_err("Failed to set given tracer: %s\n", p);`
`286`	`286`	`}`
	`287`	`+`
	`288`	`+ /* Since tracer can free snapshot buffer, allocate snapshot here.*/`
	`289`	`+ if (xbc_node_find_value(node, "alloc_snapshot", NULL)) {`
	`290`	`+ if (tracing_alloc_snapshot_instance(tr) < 0)`
	`291`	`+ pr_err("Failed to allocate snapshot buffer\n");`
	`292`	`+ }`
`287`	`293`	`}`
`288`	`294`
`289`	`295`	`static void __init`