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Subject[for-next][PATCH 2/3] ring-buffer: Remove useless unused tracing_off_permanent()
From: "Steven Rostedt (Red Hat)" <rostedt@goodmis.org>

The tracing_off_permanent() call is a way to disable all ring_buffers.
Nothing uses it and nothing should use it, as tracing_off() and
friends are better, as they disable the ring buffers related to
tracing. The tracing_off_permanent() even disabled non tracing
ring buffers. This is a bit drastic, and was added to handle NMIs
doing outputs that could corrupt the ring buffer when only tracing
used them. It is now obsolete and adds a little overhead, it should
be removed.

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
include/linux/kernel.h | 6 -----
kernel/trace/ring_buffer.c | 61 ----------------------------------------------
2 files changed, 67 deletions(-)

diff --git a/include/linux/kernel.h b/include/linux/kernel.h
index 3a5b48e52a9e..d948718a83d7 100644
--- a/include/linux/kernel.h
+++ b/include/linux/kernel.h
@@ -532,12 +532,6 @@ bool mac_pton(const char *s, u8 *mac);
*
* Most likely, you want to use tracing_on/tracing_off.
*/
-#ifdef CONFIG_RING_BUFFER
-/* trace_off_permanent stops recording with no way to bring it back */
-void tracing_off_permanent(void);
-#else
-static inline void tracing_off_permanent(void) { }
-#endif

enum ftrace_dump_mode {
DUMP_NONE,
diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index e9420fdc7409..0fc5add6423b 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -115,63 +115,11 @@ int ring_buffer_print_entry_header(struct trace_seq *s)
*
*/

-/*
- * A fast way to enable or disable all ring buffers is to
- * call tracing_on or tracing_off. Turning off the ring buffers
- * prevents all ring buffers from being recorded to.
- * Turning this switch on, makes it OK to write to the
- * ring buffer, if the ring buffer is enabled itself.
- *
- * There's three layers that must be on in order to write
- * to the ring buffer.
- *
- * 1) This global flag must be set.
- * 2) The ring buffer must be enabled for recording.
- * 3) The per cpu buffer must be enabled for recording.
- *
- * In case of an anomaly, this global flag has a bit set that
- * will permantly disable all ring buffers.
- */
-
-/*
- * Global flag to disable all recording to ring buffers
- * This has two bits: ON, DISABLED
- *
- * ON DISABLED
- * ---- ----------
- * 0 0 : ring buffers are off
- * 1 0 : ring buffers are on
- * X 1 : ring buffers are permanently disabled
- */
-
-enum {
- RB_BUFFERS_ON_BIT = 0,
- RB_BUFFERS_DISABLED_BIT = 1,
-};
-
-enum {
- RB_BUFFERS_ON = 1 << RB_BUFFERS_ON_BIT,
- RB_BUFFERS_DISABLED = 1 << RB_BUFFERS_DISABLED_BIT,
-};
-
-static unsigned long ring_buffer_flags __read_mostly = RB_BUFFERS_ON;
-
/* Used for individual buffers (after the counter) */
#define RB_BUFFER_OFF (1 << 20)

#define BUF_PAGE_HDR_SIZE offsetof(struct buffer_data_page, data)

-/**
- * tracing_off_permanent - permanently disable ring buffers
- *
- * This function, once called, will disable all ring buffers
- * permanently.
- */
-void tracing_off_permanent(void)
-{
- set_bit(RB_BUFFERS_DISABLED_BIT, &ring_buffer_flags);
-}
-
#define RB_EVNT_HDR_SIZE (offsetof(struct ring_buffer_event, array))
#define RB_ALIGNMENT 4U
#define RB_MAX_SMALL_DATA (RB_ALIGNMENT * RINGBUF_TYPE_DATA_TYPE_LEN_MAX)
@@ -2728,9 +2676,6 @@ ring_buffer_lock_reserve(struct ring_buffer *buffer, unsigned long length)
struct ring_buffer_event *event;
int cpu;

- if (ring_buffer_flags != RB_BUFFERS_ON)
- return NULL;
-
/* If we are tracing schedule, we don't want to recurse */
preempt_disable_notrace();

@@ -2992,9 +2937,6 @@ int ring_buffer_write(struct ring_buffer *buffer,
int ret = -EBUSY;
int cpu;

- if (ring_buffer_flags != RB_BUFFERS_ON)
- return -EBUSY;
-
preempt_disable_notrace();

if (atomic_read(&buffer->record_disabled))
@@ -4350,9 +4292,6 @@ int ring_buffer_swap_cpu(struct ring_buffer *buffer_a,

ret = -EAGAIN;

- if (ring_buffer_flags != RB_BUFFERS_ON)
- goto out;
-
if (atomic_read(&buffer_a->record_disabled))
goto out;

--
2.1.4



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