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Commit a32c7765 authored by Li Zefan's avatar Li Zefan Committed by Ingo Molnar
Browse files

tracing: Fix stack tracer sysctl handling 



This made my machine completely frozen:

  # echo 1 > /proc/sys/kernel/stack_tracer_enabled
  # echo 2 > /proc/sys/kernel/stack_tracer_enabled

The cause is register_ftrace_function() was called twice.

Also fix ftrace_enabled sysctl, though seems nothing bad happened
as I tested it.

Signed-off-by: default avatarLi Zefan <lizf@cn.fujitsu.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
LKML-Reference: <4A448D17.9010305@cn.fujitsu.com>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 0296e425

kernel/trace/ftrace.c

+2 −2
Original line number Diff line number Diff line
@@ -3160,10 +3160,10 @@ ftrace_enable_sysctl(struct ctl_table *table, int write, 


	ret  = proc_dointvec(table, write, file, buffer, lenp, ppos);



	if (ret || !write || (last_ftrace_enabled == ftrace_enabled))

	if (ret || !write || (last_ftrace_enabled == !!ftrace_enabled))

		goto out;



	last_ftrace_enabled = ftrace_enabled;

	last_ftrace_enabled = !!ftrace_enabled;



	if (ftrace_enabled) {

kernel/trace/trace_stack.c

+2 −2
Original line number Diff line number Diff line
@@ -326,10 +326,10 @@ stack_trace_sysctl(struct ctl_table *table, int write, 
	ret = proc_dointvec(table, write, file, buffer, lenp, ppos);



	if (ret || !write ||

	    (last_stack_tracer_enabled == stack_tracer_enabled))

	    (last_stack_tracer_enabled == !!stack_tracer_enabled))

		goto out;



	last_stack_tracer_enabled = stack_tracer_enabled;

	last_stack_tracer_enabled = !!stack_tracer_enabled;



	if (stack_tracer_enabled)

		register_ftrace_function(&trace_ops);