Commit 86b3de60 authored by Steven Rostedt (VMware)'s avatar Steven Rostedt (VMware)
Browse files

ring-buffer: Remove HAVE_64BIT_ALIGNED_ACCESS 



Commit c19fa94a ("Add HAVE_64BIT_ALIGNED_ACCESS") added the config for
architectures that required 64bit aligned access for all 64bit words. As
the ftrace ring buffer stores data on 4 byte alignment, this config option
was used to force it to store data on 8 byte alignment to make sure the data
being stored and written directly into the ring buffer was 8 byte aligned as
it would cause issues trying to write an 8 byte word on a 4 not 8 byte
aligned memory location.

But with the removal of the metag architecture, which was the only
architecture to use this, there is no architecture supported by Linux that
requires 8 byte aligne access for all 8 byte words (4 byte alignment is good
enough). Removing this config can simplify the code a bit.

Signed-off-by: default avatarSteven Rostedt (VMware) <rostedt@goodmis.org>
parent a124692b

arch/Kconfig

+0 −16
Original line number Diff line number Diff line
@@ -128,22 +128,6 @@ config UPROBES 
	    managed by the kernel and kept transparent to the probed

	    application. )



config HAVE_64BIT_ALIGNED_ACCESS

	def_bool 64BIT && !HAVE_EFFICIENT_UNALIGNED_ACCESS

	help

	  Some architectures require 64 bit accesses to be 64 bit

	  aligned, which also requires structs containing 64 bit values

	  to be 64 bit aligned too. This includes some 32 bit

	  architectures which can do 64 bit accesses, as well as 64 bit

	  architectures without unaligned access.



	  This symbol should be selected by an architecture if 64 bit

	  accesses are required to be 64 bit aligned in this way even

	  though it is not a 64 bit architecture.



	  See Documentation/unaligned-memory-access.txt for more

	  information on the topic of unaligned memory accesses.



config HAVE_EFFICIENT_UNALIGNED_ACCESS

	bool

	help

kernel/trace/ring_buffer.c

+4 −13
Original line number Diff line number Diff line
@@ -128,16 +128,7 @@ int ring_buffer_print_entry_header(struct trace_seq *s) 
#define RB_ALIGNMENT		4U

#define RB_MAX_SMALL_DATA	(RB_ALIGNMENT * RINGBUF_TYPE_DATA_TYPE_LEN_MAX)

#define RB_EVNT_MIN_SIZE	8U	/* two 32bit words */



#ifndef CONFIG_HAVE_64BIT_ALIGNED_ACCESS

# define RB_FORCE_8BYTE_ALIGNMENT	0

# define RB_ARCH_ALIGNMENT		RB_ALIGNMENT

#else

# define RB_FORCE_8BYTE_ALIGNMENT	1

# define RB_ARCH_ALIGNMENT		8U

#endif



#define RB_ALIGN_DATA		__aligned(RB_ARCH_ALIGNMENT)

#define RB_ALIGN_DATA		__aligned(RB_ALIGNMENT)



/* define RINGBUF_TYPE_DATA for 'case RINGBUF_TYPE_DATA:' */

#define RINGBUF_TYPE_DATA 0 ... RINGBUF_TYPE_DATA_TYPE_LEN_MAX
@@ -2373,7 +2364,7 @@ rb_update_event(struct ring_buffer_per_cpu *cpu_buffer, 


	event->time_delta = delta;

	length -= RB_EVNT_HDR_SIZE;

	if (length > RB_MAX_SMALL_DATA || RB_FORCE_8BYTE_ALIGNMENT) {

	if (length > RB_MAX_SMALL_DATA) {

		event->type_len = 0;

		event->array[0] = length;

	} else
@@ -2388,11 +2379,11 @@ static unsigned rb_calculate_event_length(unsigned length) 
	if (!length)

		length++;



	if (length > RB_MAX_SMALL_DATA || RB_FORCE_8BYTE_ALIGNMENT)

	if (length > RB_MAX_SMALL_DATA)

		length += sizeof(event.array[0]);



	length += RB_EVNT_HDR_SIZE;

	length = ALIGN(length, RB_ARCH_ALIGNMENT);

	length = ALIGN(length, RB_ALIGNMENT);



	/*

	 * In case the time delta is larger than the 27 bits for it

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