tracing: Fix stack tracer sysctl handling (a32c7765) · Commits · 戴 / test

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:

Li 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:

Ingo Molnar <mingo@elte.hu>

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);

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