Messages in this thread | | | Date | Mon, 2 Feb 2009 19:50:21 -0800 | From | Andrew Morton <> | Subject | Re: [PATCH 2/3] trace: fix default boot up tracer |
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On Mon, 02 Feb 2009 21:38:32 -0500 Steven Rostedt <rostedt@goodmis.org> wrote:
> @@ -510,8 +520,25 @@ int register_tracer(struct tracer *type) > out: > tracing_selftest_running = false; > mutex_unlock(&trace_types_lock); > - lock_kernel(); > > + if (!ret && default_bootup_tracer) { > + if (!strncmp(default_bootup_tracer, type->name, > + BOOTUP_TRACER_SIZE)) { > + printk(KERN_INFO "Starting tracer '%s'\n", > + type->name); > + /* Do we want this tracer to start on bootup? */ > + tracing_set_tracer(type->name); > + default_bootup_tracer = NULL; > + /* disable other selftests, since this will break it. */ > + tracing_selftest_disabled = 1; > +#ifdef CONFIG_FTRACE_STARTUP_TEST > + printk(KERN_INFO "Disabling FTRACE selftests due" > + " to running tracer '%s'\n", type->name); > +#endif > + } > + } > + > + lock_kernel(); > return ret; > }
The fun and games which register_tracer() plays with lock_kernel() tell us that this function is only called at bootup time and hence could be __init. A quick whizz through callers confirms that.
And if register_tracer() is also only callable at bootup, one suspects that unregister_tracer() isn't useful. And lo, it has no callers.
This leads one to further surmise that trace_types_lock a) could be __initdata and b) could be removed (the list is only altered when we're running single-threaded). This appears to be the case.
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