ring-buffer: Remove HAVE_64BIT_ALIGNED_ACCESS

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>

diff --git a/arch/Kconfig b/arch/Kconfig
index c47b328..665a755 100644 (file)
--- 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 05b0b31..66358d6 100644 (file)
--- 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