Commit f1affcaa authored by Steven Rostedt (Red Hat)'s avatar Steven Rostedt (Red Hat) Committed by Steven Rostedt
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tracing: Add snapshot in the per_cpu trace directories 



Add the snapshot file into the per_cpu tracing directories to allow
them to be read for an individual cpu. This also allows to clear
an individual cpu from the snapshot buffer.

If the kernel allows it (CONFIG_RING_BUFFER_ALLOW_SWAP is set), then
echoing in '1' into one of the per_cpu snapshot files will do an
individual cpu buffer swap instead of the entire file.

Cc: Hiraku Toyooka <hiraku.toyooka.gu@hitachi.com>
Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
parent 12883efb

kernel/trace/trace.c

+56 −10
Original line number Diff line number Diff line
@@ -2436,6 +2436,31 @@ static void test_ftrace_alive(struct seq_file *m) 
}



#ifdef CONFIG_TRACER_MAX_TRACE

static void show_snapshot_main_help(struct seq_file *m)

{

	seq_printf(m, "# echo 0 > snapshot : Clears and frees snapshot buffer\n");

	seq_printf(m, "# echo 1 > snapshot : Allocates snapshot buffer, if not already allocated.\n");

	seq_printf(m, "#                      Takes a snapshot of the main buffer.\n");

	seq_printf(m, "# echo 2 > snapshot : Clears snapshot buffer (but does not allocate)\n");

	seq_printf(m, "#                      (Doesn't have to be '2' works with any number that\n");

	seq_printf(m, "#                       is not a '0' or '1')\n");

}



static void show_snapshot_percpu_help(struct seq_file *m)

{

	seq_printf(m, "# echo 0 > snapshot : Invalid for per_cpu snapshot file.\n");

#ifdef CONFIG_RING_BUFFER_ALLOW_SWAP

	seq_printf(m, "# echo 1 > snapshot : Allocates snapshot buffer, if not already allocated.\n");

	seq_printf(m, "#                      Takes a snapshot of the main buffer for this cpu.\n");

#else

	seq_printf(m, "# echo 1 > snapshot : Not supported with this kernel.\n");

	seq_printf(m, "#                     Must use main snapshot file to allocate.\n");

#endif

	seq_printf(m, "# echo 2 > snapshot : Clears this cpu's snapshot buffer (but does not allocate)\n");

	seq_printf(m, "#                      (Doesn't have to be '2' works with any number that\n");

	seq_printf(m, "#                       is not a '0' or '1')\n");

}



static void print_snapshot_help(struct seq_file *m, struct trace_iterator *iter)

{

	if (iter->trace->allocated_snapshot)
@@ -2444,12 +2469,10 @@ static void print_snapshot_help(struct seq_file *m, struct trace_iterator *iter) 
		seq_printf(m, "#\n# * Snapshot is freed *\n#\n");



	seq_printf(m, "# Snapshot commands:\n");

	seq_printf(m, "# echo 0 > snapshot : Clears and frees snapshot buffer\n");

	seq_printf(m, "# echo 1 > snapshot : Allocates snapshot buffer, if not already allocated.\n");

	seq_printf(m, "#                      Takes a snapshot of the main buffer.\n");

	seq_printf(m, "# echo 2 > snapshot : Clears snapshot buffer (but does not allocate)\n");

	seq_printf(m, "#                      (Doesn't have to be '2' works with any number that\n");

	seq_printf(m, "#                       is not a '0' or '1')\n");

	if (iter->cpu_file == RING_BUFFER_ALL_CPUS)

		show_snapshot_main_help(m);

	else

		show_snapshot_percpu_help(m);

}

#else

/* Should never be called */
@@ -4207,6 +4230,7 @@ static int tracing_snapshot_open(struct inode *inode, struct file *file) 
		}

		iter->tr = tc->tr;

		iter->trace_buffer = &tc->tr->max_buffer;

		iter->cpu_file = tc->cpu;

		m->private = iter;

		file->private_data = m;

	}
@@ -4241,6 +4265,10 @@ tracing_snapshot_write(struct file *filp, const char __user *ubuf, size_t cnt, 


	switch (val) {

	case 0:

		if (iter->cpu_file != RING_BUFFER_ALL_CPUS) {

			ret = -EINVAL;

			break;

		}

		if (tr->current_trace->allocated_snapshot) {

			/* free spare buffer */

			ring_buffer_resize(tr->max_buffer.buffer, 1,
@@ -4251,6 +4279,13 @@ tracing_snapshot_write(struct file *filp, const char __user *ubuf, size_t cnt, 
		}

		break;

	case 1:

/* Only allow per-cpu swap if the ring buffer supports it */

#ifndef CONFIG_RING_BUFFER_ALLOW_SWAP

		if (iter->cpu_file != RING_BUFFER_ALL_CPUS) {

			ret = -EINVAL;

			break;

		}

#endif

		if (!tr->current_trace->allocated_snapshot) {

			/* allocate spare buffer */

			ret = resize_buffer_duplicate_size(&tr->max_buffer,
@@ -4259,15 +4294,21 @@ tracing_snapshot_write(struct file *filp, const char __user *ubuf, size_t cnt, 
				break;

			tr->current_trace->allocated_snapshot = true;

		}



		local_irq_disable();

		/* Now, we're going to swap */

		if (iter->cpu_file == RING_BUFFER_ALL_CPUS)

			update_max_tr(&global_trace, current, smp_processor_id());

		else

			update_max_tr_single(&global_trace, current, iter->cpu_file);

		local_irq_enable();

		break;

	default:

		if (tr->current_trace->allocated_snapshot)

		if (tr->current_trace->allocated_snapshot) {

			if (iter->cpu_file == RING_BUFFER_ALL_CPUS)

				tracing_reset_online_cpus(&tr->max_buffer);

			else

				tracing_reset(&tr->max_buffer, iter->cpu_file);

		}

		break;

	}
@@ -4835,6 +4876,11 @@ tracing_init_debugfs_percpu(struct trace_array *tr, long cpu) 


	trace_create_file("buffer_size_kb", 0444, d_cpu,

			(void *)&data->trace_cpu, &tracing_entries_fops);



#ifdef CONFIG_TRACER_SNAPSHOT

	trace_create_file("snapshot", 0644, d_cpu,

			  (void *)&data->trace_cpu, &snapshot_fops);

#endif

}



#ifdef CONFIG_FTRACE_SELFTEST

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