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ring-buffer: Remove useless unused tracing_off_permanent()

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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>
This commit is contained in:
Steven Rostedt (Red Hat) 2015-05-28 13:21:34 -04:00 • committed by Steven Rostedt
commit 3c6296f716
2 changed files with 0 additions and 67 deletions
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6
include/linux/kernel.h
View file

@ -532,12 +532,6 @@ bool mac_pton(const char *s, u8 *mac);
* *
* Most likely, you want to use tracing_on/tracing_off. * 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 { enum ftrace_dump_mode {
DUMP_NONE, DUMP_NONE,

61
kernel/trace/ring_buffer.c
View file

@ -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) */ /* Used for individual buffers (after the counter) */
#define RB_BUFFER_OFF (1 << 20) #define RB_BUFFER_OFF (1 << 20)
#define BUF_PAGE_HDR_SIZE offsetof(struct buffer_data_page, data) #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_EVNT_HDR_SIZE (offsetof(struct ring_buffer_event, array))
#define RB_ALIGNMENT 4U #define RB_ALIGNMENT 4U
#define RB_MAX_SMALL_DATA (RB_ALIGNMENT * RINGBUF_TYPE_DATA_TYPE_LEN_MAX) #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; struct ring_buffer_event *event;
int cpu; int cpu;
if (ring_buffer_flags != RB_BUFFERS_ON)
return NULL;
/* If we are tracing schedule, we don't want to recurse */ /* If we are tracing schedule, we don't want to recurse */
preempt_disable_notrace(); preempt_disable_notrace();
@ -2992,9 +2937,6 @@ int ring_buffer_write(struct ring_buffer *buffer,
int ret = -EBUSY; int ret = -EBUSY;
int cpu; int cpu;
if (ring_buffer_flags != RB_BUFFERS_ON)
return -EBUSY;
preempt_disable_notrace(); preempt_disable_notrace();
if (atomic_read(&buffer->record_disabled)) if (atomic_read(&buffer->record_disabled))
@ -4350,9 +4292,6 @@ int ring_buffer_swap_cpu(struct ring_buffer *buffer_a,
ret = -EAGAIN; ret = -EAGAIN;
if (ring_buffer_flags != RB_BUFFERS_ON)
goto out;
if (atomic_read(&buffer_a->record_disabled)) if (atomic_read(&buffer_a->record_disabled))
goto out; goto out;