Commit 3e1f60b8 authored Mar 22, 2009 by Frederic Weisbecker Committed by Ingo Molnar Mar 23, 2009

tracing/ftrace: check if debugfs is registered before creating files



Impact: fix a crash with ftrace={nop,boot} parameter

If the nop or initcall tracers are launched as boot tracers,
they will attempt to create their option directory and files.
But these tracers are registered very early and then assigned
as "boot tracers" very early if asked to.

Since they do this before debugfs has been registered (core initcall),
a crash is triggered.

Another early tracers could also come later. So we fix it by
checking if debugfs is initialized before creating the root
tracing directory.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Greg Kroah-Hartman <gregkh@suse.de>
Cc: Steven Rostedt <rostedt@goodmis.org>
LKML-Reference: <1237759847-21025-3-git-send-email-fweisbec@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

parent c0f92ba9

kernel/trace/trace.c

+3 −0

Original line number	Diff line number	Diff line
		@@ -3513,6 +3513,9 @@ struct dentry *tracing_init_dentry(void)
		if (d_tracer)
		return d_tracer;

		if (!debugfs_initialized())
		return NULL;

		d_tracer = debugfs_create_dir("tracing", NULL);

		if (!d_tracer && !once) {

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