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

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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: Sean Paul <sean@poorly.run>
Reviewed-by: Sean Paul <sean@poorly.run>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
This commit is contained in:
Steven Rostedt (VMware) 2020-08-06 12:46:49 -04:00
parent 10de795a5a
commit 38ce2a9e33
2 changed files with 45 additions and 0 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

1
include/linux/trace.h
View file

@ -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);

44
kernel/trace/trace.c
View file

@ -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, ...)