Commit 55034cd6 authored by Steven Rostedt (Red Hat)'s avatar Steven Rostedt (Red Hat) Committed by Steven Rostedt
Browse files

tracing: Add alloc_snapshot kernel command line parameter 



If debugging the kernel, and the developer wants to use
tracing_snapshot() in places where tracing_snapshot_alloc() may
be difficult (or more likely, the developer is lazy and doesn't
want to bother with tracing_snapshot_alloc() at all), then adding

  alloc_snapshot

to the kernel command line parameter will tell ftrace to allocate
the snapshot buffer (if configured) when it allocates the main
tracing buffer.

I also noticed that ring_buffer_expanded and tracing_selftest_disabled
had inconsistent use of boolean "true" and "false" with "0" and "1".
I cleaned that up too.

Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
parent f4e781c0

Documentation/kernel-parameters.txt

+7 −0
Original line number Diff line number Diff line
@@ -320,6 +320,13 @@ bytes respectively. Such letter suffixes can also be entirely omitted. 
			on: enable for both 32- and 64-bit processes

			off: disable for both 32- and 64-bit processes



	alloc_snapshot	[FTRACE]

			Allocate the ftrace snapshot buffer on boot up when the

			main buffer is allocated. This is handy if debugging

			and you need to use tracing_snapshot() on boot up, and

			do not want to use tracing_snapshot_alloc() as it needs

			to be done where GFP_KERNEL allocations are allowed.



	amd_iommu=	[HW,X86-64]

			Pass parameters to the AMD IOMMU driver in the system.

			Possible values are:

kernel/trace/trace.c

+48 −33
Original line number Diff line number Diff line
@@ -47,7 +47,7 @@ 
 * On boot up, the ring buffer is set to the minimum size, so that

 * we do not waste memory on systems that are not using tracing.

 */

int ring_buffer_expanded;

bool ring_buffer_expanded;



/*

 * We need to change this state when a selftest is running.
@@ -121,12 +121,14 @@ static int tracing_set_tracer(const char *buf); 
static char bootup_tracer_buf[MAX_TRACER_SIZE] __initdata;

static char *default_bootup_tracer;



static bool allocate_snapshot;



static int __init set_cmdline_ftrace(char *str)

{

	strncpy(bootup_tracer_buf, str, MAX_TRACER_SIZE);

	default_bootup_tracer = bootup_tracer_buf;

	/* We are using ftrace early, expand it */

	ring_buffer_expanded = 1;

	ring_buffer_expanded = true;

	return 1;

}

__setup("ftrace=", set_cmdline_ftrace);
@@ -147,6 +149,15 @@ static int __init set_ftrace_dump_on_oops(char *str) 
}

__setup("ftrace_dump_on_oops", set_ftrace_dump_on_oops);



static int __init alloc_snapshot(char *str)

{

	allocate_snapshot = true;

	/* We also need the main ring buffer expanded */

	ring_buffer_expanded = true;

	return 1;

}

__setup("alloc_snapshot", alloc_snapshot);





static char trace_boot_options_buf[MAX_TRACER_SIZE] __initdata;

static char *trace_boot_options __initdata;
@@ -951,7 +962,7 @@ int register_tracer(struct tracer *type) 
	tracing_set_tracer(type->name);

	default_bootup_tracer = NULL;

	/* disable other selftests, since this will break it. */

	tracing_selftest_disabled = 1;

	tracing_selftest_disabled = true;

#ifdef CONFIG_FTRACE_STARTUP_TEST

	printk(KERN_INFO "Disabling FTRACE selftests due to running tracer '%s'\n",

	       type->name);
@@ -3318,7 +3329,7 @@ static int __tracing_resize_ring_buffer(struct trace_array *tr, 
	 * we use the size that was given, and we can forget about

	 * expanding it later.

	 */

	ring_buffer_expanded = 1;

	ring_buffer_expanded = true;



	/* May be called before buffers are initialized */

	if (!tr->trace_buffer.buffer)
@@ -5396,53 +5407,57 @@ static void init_trace_buffers(struct trace_array *tr, struct trace_buffer *buf) 
	}

}



static int allocate_trace_buffers(struct trace_array *tr, int size)

static int

allocate_trace_buffer(struct trace_array *tr, struct trace_buffer *buf, int size)

{

	enum ring_buffer_flags rb_flags;



	rb_flags = trace_flags & TRACE_ITER_OVERWRITE ? RB_FL_OVERWRITE : 0;



	tr->trace_buffer.buffer = ring_buffer_alloc(size, rb_flags);

	if (!tr->trace_buffer.buffer)

		goto out_free;

	buf->buffer = ring_buffer_alloc(size, rb_flags);

	if (!buf->buffer)

		return -ENOMEM;



	tr->trace_buffer.data = alloc_percpu(struct trace_array_cpu);

	if (!tr->trace_buffer.data)

		goto out_free;

	buf->data = alloc_percpu(struct trace_array_cpu);

	if (!buf->data) {

		ring_buffer_free(buf->buffer);

		return -ENOMEM;

	}



	init_trace_buffers(tr, &tr->trace_buffer);

	init_trace_buffers(tr, buf);



	/* Allocate the first page for all buffers */

	set_buffer_entries(&tr->trace_buffer,

			   ring_buffer_size(tr->trace_buffer.buffer, 0));



#ifdef CONFIG_TRACER_MAX_TRACE



	tr->max_buffer.buffer = ring_buffer_alloc(1, rb_flags);

	if (!tr->max_buffer.buffer)

		goto out_free;



	tr->max_buffer.data = alloc_percpu(struct trace_array_cpu);

	if (!tr->max_buffer.data)

		goto out_free;

	return 0;

}



	init_trace_buffers(tr, &tr->max_buffer);

static int allocate_trace_buffers(struct trace_array *tr, int size)

{

	int ret;



	set_buffer_entries(&tr->max_buffer, 1);

#endif

	return 0;

	ret = allocate_trace_buffer(tr, &tr->trace_buffer, size);

	if (ret)

		return ret;



 out_free:

	if (tr->trace_buffer.buffer)

#ifdef CONFIG_TRACER_MAX_TRACE

	ret = allocate_trace_buffer(tr, &tr->max_buffer,

				    allocate_snapshot ? size : 1);

	if (WARN_ON(ret)) {

		ring_buffer_free(tr->trace_buffer.buffer);

		free_percpu(tr->trace_buffer.data);

		return -ENOMEM;

	}

	tr->allocated_snapshot = allocate_snapshot;



#ifdef CONFIG_TRACER_MAX_TRACE

	if (tr->max_buffer.buffer)

		ring_buffer_free(tr->max_buffer.buffer);

	free_percpu(tr->max_buffer.data);

	/*

	 * Only the top level trace array gets its snapshot allocated

	 * from the kernel command line.

	 */

	allocate_snapshot = false;

#endif

	return -ENOMEM;

	return 0;

}



static int new_instance_create(const char *name)

kernel/trace/trace.h

+1 −1
Original line number Diff line number Diff line
@@ -660,7 +660,7 @@ extern int DYN_FTRACE_TEST_NAME(void); 
#define DYN_FTRACE_TEST_NAME2 trace_selftest_dynamic_test_func2

extern int DYN_FTRACE_TEST_NAME2(void);



extern int ring_buffer_expanded;

extern bool ring_buffer_expanded;

extern bool tracing_selftest_disabled;

DECLARE_PER_CPU(int, ftrace_cpu_disabled);

kernel/trace/trace_events.c

+2 −2
Original line number Diff line number Diff line
@@ -1844,8 +1844,8 @@ static char bootup_event_buf[COMMAND_LINE_SIZE] __initdata; 
static __init int setup_trace_event(char *str)

{

	strlcpy(bootup_event_buf, str, COMMAND_LINE_SIZE);

	ring_buffer_expanded = 1;

	tracing_selftest_disabled = 1;

	ring_buffer_expanded = true;

	tracing_selftest_disabled = true;



	return 1;

}

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