a358324466
Impact: enable/disable ring buffer recording API added
Several kernel developers have requested that there be a way to stop
recording into the ring buffers with a simple switch that can also
be enabled from userspace. This patch addes a new kernel API to the
ring buffers called:
tracing_on()
tracing_off()
When tracing_off() is called, all ring buffers will not be able to record
into their buffers.
tracing_on() will enable the ring buffers again.
These two act like an on/off switch. That is, there is no counting of the
number of times tracing_off or tracing_on has been called.
A new file is added to the debugfs/tracing directory called
tracing_on
This allows for userspace applications to also flip the switch.
echo 0 > debugfs/tracing/tracing_on
disables the tracing.
echo 1 > /debugfs/tracing/tracing_on
enables it.
Note, this does not disable or enable any tracers. It only sets or clears
a flag that needs to be set in order for the ring buffers to write to
their buffers. It is a global flag, and affects all ring buffers.
The buffers start out with tracing_on enabled.
There are now three flags that control recording into the buffers:
tracing_on: which affects all ring buffer tracers.
buffer->record_disabled: which affects an allocated buffer, which may be set
if an anomaly is detected, and tracing is disabled.
cpu_buffer->record_disabled: which is set by tracing_stop() or if an
anomaly is detected. tracing_start can not reenable this if
an anomaly occurred.
The userspace debugfs/tracing/tracing_enabled is implemented with
tracing_stop() but the user space code can not enable it if the kernel
called tracing_stop().
Userspace can enable the tracing_on even if the kernel disabled it.
It is just a switch used to stop tracing if a condition was hit.
tracing_on is not for protecting critical areas in the kernel nor is
it for stopping tracing if an anomaly occurred. This is because userspace
can reenable it at any time.
Side effect: With this patch, I discovered a dead variable in ftrace.c
called tracing_on. This patch removes it.
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
130 lines
3.8 KiB
C
130 lines
3.8 KiB
C
#ifndef _LINUX_RING_BUFFER_H
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#define _LINUX_RING_BUFFER_H
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#include <linux/mm.h>
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#include <linux/seq_file.h>
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struct ring_buffer;
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struct ring_buffer_iter;
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/*
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* Don't reference this struct directly, use functions below.
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*/
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struct ring_buffer_event {
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u32 type:2, len:3, time_delta:27;
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u32 array[];
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};
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/**
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* enum ring_buffer_type - internal ring buffer types
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*
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* @RINGBUF_TYPE_PADDING: Left over page padding
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* array is ignored
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* size is variable depending on how much
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* padding is needed
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*
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* @RINGBUF_TYPE_TIME_EXTEND: Extend the time delta
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* array[0] = time delta (28 .. 59)
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* size = 8 bytes
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*
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* @RINGBUF_TYPE_TIME_STAMP: Sync time stamp with external clock
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* array[0] = tv_nsec
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* array[1] = tv_sec
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* size = 16 bytes
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*
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* @RINGBUF_TYPE_DATA: Data record
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* If len is zero:
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* array[0] holds the actual length
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* array[1..(length+3)/4-1] holds data
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* else
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* length = len << 2
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* array[0..(length+3)/4] holds data
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*/
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enum ring_buffer_type {
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RINGBUF_TYPE_PADDING,
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RINGBUF_TYPE_TIME_EXTEND,
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/* FIXME: RINGBUF_TYPE_TIME_STAMP not implemented */
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RINGBUF_TYPE_TIME_STAMP,
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RINGBUF_TYPE_DATA,
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};
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unsigned ring_buffer_event_length(struct ring_buffer_event *event);
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void *ring_buffer_event_data(struct ring_buffer_event *event);
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/**
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* ring_buffer_event_time_delta - return the delta timestamp of the event
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* @event: the event to get the delta timestamp of
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*
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* The delta timestamp is the 27 bit timestamp since the last event.
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*/
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static inline unsigned
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ring_buffer_event_time_delta(struct ring_buffer_event *event)
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{
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return event->time_delta;
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}
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/*
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* size is in bytes for each per CPU buffer.
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*/
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struct ring_buffer *
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ring_buffer_alloc(unsigned long size, unsigned flags);
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void ring_buffer_free(struct ring_buffer *buffer);
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int ring_buffer_resize(struct ring_buffer *buffer, unsigned long size);
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struct ring_buffer_event *
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ring_buffer_lock_reserve(struct ring_buffer *buffer,
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unsigned long length,
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unsigned long *flags);
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int ring_buffer_unlock_commit(struct ring_buffer *buffer,
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struct ring_buffer_event *event,
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unsigned long flags);
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int ring_buffer_write(struct ring_buffer *buffer,
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unsigned long length, void *data);
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struct ring_buffer_event *
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ring_buffer_peek(struct ring_buffer *buffer, int cpu, u64 *ts);
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struct ring_buffer_event *
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ring_buffer_consume(struct ring_buffer *buffer, int cpu, u64 *ts);
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struct ring_buffer_iter *
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ring_buffer_read_start(struct ring_buffer *buffer, int cpu);
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void ring_buffer_read_finish(struct ring_buffer_iter *iter);
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struct ring_buffer_event *
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ring_buffer_iter_peek(struct ring_buffer_iter *iter, u64 *ts);
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struct ring_buffer_event *
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ring_buffer_read(struct ring_buffer_iter *iter, u64 *ts);
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void ring_buffer_iter_reset(struct ring_buffer_iter *iter);
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int ring_buffer_iter_empty(struct ring_buffer_iter *iter);
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unsigned long ring_buffer_size(struct ring_buffer *buffer);
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void ring_buffer_reset_cpu(struct ring_buffer *buffer, int cpu);
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void ring_buffer_reset(struct ring_buffer *buffer);
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int ring_buffer_swap_cpu(struct ring_buffer *buffer_a,
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struct ring_buffer *buffer_b, int cpu);
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int ring_buffer_empty(struct ring_buffer *buffer);
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int ring_buffer_empty_cpu(struct ring_buffer *buffer, int cpu);
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void ring_buffer_record_disable(struct ring_buffer *buffer);
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void ring_buffer_record_enable(struct ring_buffer *buffer);
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void ring_buffer_record_disable_cpu(struct ring_buffer *buffer, int cpu);
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void ring_buffer_record_enable_cpu(struct ring_buffer *buffer, int cpu);
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unsigned long ring_buffer_entries(struct ring_buffer *buffer);
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unsigned long ring_buffer_overruns(struct ring_buffer *buffer);
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u64 ring_buffer_time_stamp(int cpu);
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void ring_buffer_normalize_time_stamp(int cpu, u64 *ts);
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void tracing_on(void);
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void tracing_off(void);
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enum ring_buffer_flags {
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RB_FL_OVERWRITE = 1 << 0,
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};
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#endif /* _LINUX_RING_BUFFER_H */
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