lkml.org 
[lkml]   [2019]   [Jun]   [25]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
From
Subject[for-next][PATCH 01/12] ring-buffer: Remove HAVE_64BIT_ALIGNED_ACCESS
From: "Steven Rostedt (VMware)" <rostedt@goodmis.org>

Commit c19fa94a8fed ("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: Steven Rostedt (VMware) <rostedt@goodmis.org>
---
arch/Kconfig | 16 ----------------
kernel/trace/ring_buffer.c | 17 ++++-------------
2 files changed, 4 insertions(+), 29 deletions(-)

diff --git a/arch/Kconfig b/arch/Kconfig
index c47b328eada0..665a7557b15c 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -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
diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index 05b0b3139ebc..66358d66c933 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -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
--
2.20.1

\
 
 \ /
  Last update: 2019-06-25 21:16    [W:0.058 / U:0.100 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site