linux-kernel - [for-next][PATCH 03/12] tracing/boot: Add ftrace.instance.*.alloc

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Message-ID: <20201014173728.487767298@goodmis.org>
Date:   Wed, 14 Oct 2020 13:36:50 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     linux-kernel@...r.kernel.org
Cc:     Ingo Molnar <mingo@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Masami Hiramatsu <mhiramat@...nel.org>
Subject: [for-next][PATCH 03/12] tracing/boot: Add ftrace.instance.*.alloc_snapshot option

From: Masami Hiramatsu <mhiramat@...nel.org>

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@...nel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@...dmis.org>
---
 kernel/trace/trace_boot.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/kernel/trace/trace_boot.c b/kernel/trace/trace_boot.c
index 754e3cf2df3a..c22a152ef0b4 100644
--- 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
-- 
2.28.0