Commit 38ce2a9e authored by Steven Rostedt (VMware)'s avatar Steven Rostedt (VMware)
Browse files

tracing: Add trace_array_init_printk() to initialize instance trace_printk() buffers 



As trace_array_printk() used with not global instances will not add noise to
the main buffer, they are OK to have in the kernel (unlike trace_printk()).
This require the subsystem to create their own tracing instance, and the
trace_array_printk() only writes into those instances.

Add trace_array_init_printk() to initialize the trace_printk() buffers
without printing out the WARNING message.

Reported-by: default avatarSean Paul <sean@poorly.run>
Reviewed-by: default avatarSean Paul <sean@poorly.run>
Signed-off-by: default avatarSteven Rostedt (VMware) <rostedt@goodmis.org>
parent 10de795a

include/linux/trace.h

+1 −0
Original line number Diff line number Diff line
@@ -29,6 +29,7 @@ struct trace_array; 
void trace_printk_init_buffers(void);

int trace_array_printk(struct trace_array *tr, unsigned long ip,

		const char *fmt, ...);

int trace_array_init_printk(struct trace_array *tr);

void trace_array_put(struct trace_array *tr);

struct trace_array *trace_array_get_by_name(const char *name);

int trace_array_destroy(struct trace_array *tr);

kernel/trace/trace.c

+44 −0
Original line number Diff line number Diff line
@@ -3129,6 +3129,9 @@ static int alloc_percpu_trace_buffer(void) 
{

	struct trace_buffer_struct *buffers;



	if (trace_percpu_buffer)

		return 0;



	buffers = alloc_percpu(struct trace_buffer_struct);

	if (MEM_FAIL(!buffers, "Could not allocate percpu trace_printk buffer"))

		return -ENOMEM;
@@ -3331,6 +3334,26 @@ int trace_array_vprintk(struct trace_array *tr, 
	return __trace_array_vprintk(tr->array_buffer.buffer, ip, fmt, args);

}



/**

 * trace_array_printk - Print a message to a specific instance

 * @tr: The instance trace_array descriptor

 * @ip: The instruction pointer that this is called from.

 * @fmt: The format to print (printf format)

 *

 * If a subsystem sets up its own instance, they have the right to

 * printk strings into their tracing instance buffer using this

 * function. Note, this function will not write into the top level

 * buffer (use trace_printk() for that), as writing into the top level

 * buffer should only have events that can be individually disabled.

 * trace_printk() is only used for debugging a kernel, and should not

 * be ever encorporated in normal use.

 *

 * trace_array_printk() can be used, as it will not add noise to the

 * top level tracing buffer.

 *

 * Note, trace_array_init_printk() must be called on @tr before this

 * can be used.

 */

__printf(3, 0)

int trace_array_printk(struct trace_array *tr,

		       unsigned long ip, const char *fmt, ...)
@@ -3355,6 +3378,27 @@ int trace_array_printk(struct trace_array *tr, 
}

EXPORT_SYMBOL_GPL(trace_array_printk);



/**

 * trace_array_init_printk - Initialize buffers for trace_array_printk()

 * @tr: The trace array to initialize the buffers for

 *

 * As trace_array_printk() only writes into instances, they are OK to

 * have in the kernel (unlike trace_printk()). This needs to be called

 * before trace_array_printk() can be used on a trace_array.

 */

int trace_array_init_printk(struct trace_array *tr)

{

	if (!tr)

		return -ENOENT;



	/* This is only allowed for created instances */

	if (tr == &global_trace)

		return -EINVAL;



	return alloc_percpu_trace_buffer();

}

EXPORT_SYMBOL_GPL(trace_array_init_printk);



__printf(3, 4)

int trace_array_printk_buf(struct trace_buffer *buffer,

			   unsigned long ip, const char *fmt, ...)