linux-kernel - Re: [PATCH 3/7] blktrace: remove blk_probe

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Date:	Fri, 20 Mar 2009 10:03:09 -0300
From:	Arnaldo Carvalho de Melo <acme@...hat.com>
To:	Li Zefan <lizf@...fujitsu.com>
Cc:	Ingo Molnar <mingo@...e.hu>, Jens Axboe <jens.axboe@...cle.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 3/7] blktrace: remove blk_probe_mutex

Em Fri, Mar 20, 2009 at 09:48:26AM +0800, Li Zefan escreveu:
> blk_register_tracepoints() always returns 0, so make it return void, thus
> we don't need to use blk_probe_mutex to protect blk_probes_ref.
> 
> Signed-off-by: Li Zefan <lizf@...fujitsu.com>

Historic reasons, when I first worked on this I found all those WARN_ONs
in blk_register_tracepoints a bogosity that should be later fixed, but
to reduce the patch size I never got around to submit the proper patch,
so I don't think that the fix is what you suggests, here it is what I
had before I removed the non-essential parts of the patch:

+static void blk_tracer_error(const char *name)
+{
+	pr_info("blk trace: Couldn't activate tracepoint "
+		"probe to block_%s\n", name);
+}
+
+#define register_trace_block(tpoint)				     \
+	ret = register_trace_block_##tpoint(blk_add_trace_##tpoint); \
+	if (ret) { 						     \
+		blk_tracer_error(#tpoint);			     \
+		goto *exit_point;		  		     \
+	} else							     \
+		exit_point = &&fail_deprobe_##tpoint;
+	
+
+#define fail_trace_block(tpoint)	\
+	fail_deprobe_##tpoint:		\
+		unregister_trace_block_##tpoint(blk_add_trace_##tpoint)
+
+static int tracing_blk_register(void)
+{
+	int ret;
+	void *exit_point = &&error;
+
+	register_trace_block(rq_abort);
+	register_trace_block(rq_insert);
+	register_trace_block(rq_issue);
+	register_trace_block(rq_requeue);
+	register_trace_block(rq_complete);
+	register_trace_block(bio_bounce);
+	register_trace_block(bio_backmerge);
+	register_trace_block(bio_frontmerge);
+	register_trace_block(bio_queue);
+	register_trace_block(getrq);
+	register_trace_block(sleeprq);
+	register_trace_block(plug);
+	register_trace_block(unplug_timer);
+	register_trace_block(unplug_io);
+	register_trace_block(split);
+	register_trace_block(remap);
+
+	return 0;
+
+	fail_trace_block(remap);
+	fail_trace_block(split);
+	fail_trace_block(unplug_io);
+	fail_trace_block(unplug_timer);
+	fail_trace_block(plug);
+	fail_trace_block(sleeprq);
+	fail_trace_block(getrq);
+	fail_trace_block(bio_queue);
+	fail_trace_block(bio_frontmerge);
+	fail_trace_block(bio_backmerge);
+	fail_trace_block(bio_bounce);
+	fail_trace_block(rq_complete);
+	fail_trace_block(rq_requeue);
+	fail_trace_block(rq_issue);
+	fail_trace_block(rq_insert);
+	fail_trace_block(rq_abort);
+error:
+	return ret;
+}
+
+static void tracing_blk_unregister(void)
+{
+	unregister_trace_block_remap(blk_add_trace_remap);
+	unregister_trace_block_split(blk_add_trace_split);
+	unregister_trace_block_unplug_io(blk_add_trace_unplug_io);
+	unregister_trace_block_unplug_timer(blk_add_trace_unplug_timer);
+	unregister_trace_block_plug(blk_add_trace_plug);
+	unregister_trace_block_sleeprq(blk_add_trace_sleeprq);
+	unregister_trace_block_getrq(blk_add_trace_getrq);
+	unregister_trace_block_bio_queue(blk_add_trace_bio_queue);
+	unregister_trace_block_bio_frontmerge(blk_add_trace_bio_frontmerge);
+	unregister_trace_block_bio_backmerge(blk_add_trace_bio_backmerge);
+	unregister_trace_block_bio_complete(blk_add_trace_bio_complete);
+	unregister_trace_block_bio_bounce(blk_add_trace_bio_bounce);
+	unregister_trace_block_rq_complete(blk_add_trace_rq_complete);
+	unregister_trace_block_rq_requeue(blk_add_trace_rq_requeue);
+	unregister_trace_block_rq_issue(blk_add_trace_rq_issue);
+	unregister_trace_block_rq_insert(blk_add_trace_rq_insert);
+	unregister_trace_block_rq_abort(blk_add_trace_rq_abort);
+	tracepoint_synchronize_unregister();
+}

Regards,

- Arnaldo
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