android_kernel_samsung_sm8650/include/linux/ftrace_event.h
Steven Rostedt 1eaa4787a7 tracing: Comment the use of event_mutex with trace event flags
The flags variable is protected by the event_mutex when modifying,
but the event_mutex is not held when reading the variable.

This is due to the fact that the reads occur in critical sections where
taking a mutex (or even a spinlock) is not wanted.

But the two flags that exist (enable and filter_active) have the code
written as such to handle the reads to not need a lock.

The enable flag is used just to know if the event is enabled or not
and its use is always under the event_mutex. Whether or not the event
is actually enabled is really determined by the tracepoint being
registered. The flag is just a way to let the code know if the tracepoint
is registered.

The filter_active is different. It is read without the lock. If it
is set, then the event probes jump to the filter code. There can be a
slight mismatch between filters available and filter_active. If the flag is
set but no filters are available, the code safely jumps to a filter nop.
If the flag is not set and the filters are available, then the filters
are skipped. This is acceptable since filters are usually set before
tracing or they are set by humans, which would not notice the slight
delay that this causes.

v2: Fixed typo: "cacheing" -> "caching"

Reported-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Acked-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Tom Zanussi <tzanussi@gmail.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2010-05-14 21:17:41 -04:00

262 lines
7.1 KiB
C

#ifndef _LINUX_FTRACE_EVENT_H
#define _LINUX_FTRACE_EVENT_H
#include <linux/ring_buffer.h>
#include <linux/trace_seq.h>
#include <linux/percpu.h>
#include <linux/hardirq.h>
#include <linux/perf_event.h>
struct trace_array;
struct tracer;
struct dentry;
DECLARE_PER_CPU(struct trace_seq, ftrace_event_seq);
struct trace_print_flags {
unsigned long mask;
const char *name;
};
const char *ftrace_print_flags_seq(struct trace_seq *p, const char *delim,
unsigned long flags,
const struct trace_print_flags *flag_array);
const char *ftrace_print_symbols_seq(struct trace_seq *p, unsigned long val,
const struct trace_print_flags *symbol_array);
/*
* The trace entry - the most basic unit of tracing. This is what
* is printed in the end as a single line in the trace output, such as:
*
* bash-15816 [01] 235.197585: idle_cpu <- irq_enter
*/
struct trace_entry {
unsigned short type;
unsigned char flags;
unsigned char preempt_count;
int pid;
int lock_depth;
};
#define FTRACE_MAX_EVENT \
((1 << (sizeof(((struct trace_entry *)0)->type) * 8)) - 1)
/*
* Trace iterator - used by printout routines who present trace
* results to users and which routines might sleep, etc:
*/
struct trace_iterator {
struct trace_array *tr;
struct tracer *trace;
void *private;
int cpu_file;
struct mutex mutex;
struct ring_buffer_iter *buffer_iter[NR_CPUS];
unsigned long iter_flags;
/* The below is zeroed out in pipe_read */
struct trace_seq seq;
struct trace_entry *ent;
unsigned long lost_events;
int leftover;
int cpu;
u64 ts;
loff_t pos;
long idx;
cpumask_var_t started;
};
struct trace_event;
typedef enum print_line_t (*trace_print_func)(struct trace_iterator *iter,
int flags, struct trace_event *event);
struct trace_event_functions {
trace_print_func trace;
trace_print_func raw;
trace_print_func hex;
trace_print_func binary;
};
struct trace_event {
struct hlist_node node;
struct list_head list;
int type;
struct trace_event_functions *funcs;
};
extern int register_ftrace_event(struct trace_event *event);
extern int unregister_ftrace_event(struct trace_event *event);
/* Return values for print_line callback */
enum print_line_t {
TRACE_TYPE_PARTIAL_LINE = 0, /* Retry after flushing the seq */
TRACE_TYPE_HANDLED = 1,
TRACE_TYPE_UNHANDLED = 2, /* Relay to other output functions */
TRACE_TYPE_NO_CONSUME = 3 /* Handled but ask to not consume */
};
void tracing_generic_entry_update(struct trace_entry *entry,
unsigned long flags,
int pc);
struct ring_buffer_event *
trace_current_buffer_lock_reserve(struct ring_buffer **current_buffer,
int type, unsigned long len,
unsigned long flags, int pc);
void trace_current_buffer_unlock_commit(struct ring_buffer *buffer,
struct ring_buffer_event *event,
unsigned long flags, int pc);
void trace_nowake_buffer_unlock_commit(struct ring_buffer *buffer,
struct ring_buffer_event *event,
unsigned long flags, int pc);
void trace_current_buffer_discard_commit(struct ring_buffer *buffer,
struct ring_buffer_event *event);
void tracing_record_cmdline(struct task_struct *tsk);
struct event_filter;
enum trace_reg {
TRACE_REG_REGISTER,
TRACE_REG_UNREGISTER,
TRACE_REG_PERF_REGISTER,
TRACE_REG_PERF_UNREGISTER,
};
struct ftrace_event_call;
struct ftrace_event_class {
char *system;
void *probe;
#ifdef CONFIG_PERF_EVENTS
void *perf_probe;
#endif
int (*reg)(struct ftrace_event_call *event,
enum trace_reg type);
int (*define_fields)(struct ftrace_event_call *);
struct list_head *(*get_fields)(struct ftrace_event_call *);
struct list_head fields;
int (*raw_init)(struct ftrace_event_call *);
};
enum {
TRACE_EVENT_FL_ENABLED_BIT,
TRACE_EVENT_FL_FILTERED_BIT,
};
enum {
TRACE_EVENT_FL_ENABLED = (1 << TRACE_EVENT_FL_ENABLED_BIT),
TRACE_EVENT_FL_FILTERED = (1 << TRACE_EVENT_FL_FILTERED_BIT),
};
struct ftrace_event_call {
struct list_head list;
struct ftrace_event_class *class;
char *name;
struct dentry *dir;
struct trace_event event;
const char *print_fmt;
struct event_filter *filter;
void *mod;
void *data;
/*
* 32 bit flags:
* bit 1: enabled
* bit 2: filter_active
*
* Changes to flags must hold the event_mutex.
*
* Note: Reads of flags do not hold the event_mutex since
* they occur in critical sections. But the way flags
* is currently used, these changes do no affect the code
* except that when a change is made, it may have a slight
* delay in propagating the changes to other CPUs due to
* caching and such.
*/
unsigned int flags;
int perf_refcount;
};
#define PERF_MAX_TRACE_SIZE 2048
#define MAX_FILTER_PRED 32
#define MAX_FILTER_STR_VAL 256 /* Should handle KSYM_SYMBOL_LEN */
extern void destroy_preds(struct ftrace_event_call *call);
extern int filter_match_preds(struct event_filter *filter, void *rec);
extern int filter_current_check_discard(struct ring_buffer *buffer,
struct ftrace_event_call *call,
void *rec,
struct ring_buffer_event *event);
enum {
FILTER_OTHER = 0,
FILTER_STATIC_STRING,
FILTER_DYN_STRING,
FILTER_PTR_STRING,
};
extern int trace_event_raw_init(struct ftrace_event_call *call);
extern int trace_define_field(struct ftrace_event_call *call, const char *type,
const char *name, int offset, int size,
int is_signed, int filter_type);
extern int trace_add_event_call(struct ftrace_event_call *call);
extern void trace_remove_event_call(struct ftrace_event_call *call);
#define is_signed_type(type) (((type)(-1)) < 0)
int trace_set_clr_event(const char *system, const char *event, int set);
/*
* The double __builtin_constant_p is because gcc will give us an error
* if we try to allocate the static variable to fmt if it is not a
* constant. Even with the outer if statement optimizing out.
*/
#define event_trace_printk(ip, fmt, args...) \
do { \
__trace_printk_check_format(fmt, ##args); \
tracing_record_cmdline(current); \
if (__builtin_constant_p(fmt)) { \
static const char *trace_printk_fmt \
__attribute__((section("__trace_printk_fmt"))) = \
__builtin_constant_p(fmt) ? fmt : NULL; \
\
__trace_bprintk(ip, trace_printk_fmt, ##args); \
} else \
__trace_printk(ip, fmt, ##args); \
} while (0)
#ifdef CONFIG_PERF_EVENTS
struct perf_event;
DECLARE_PER_CPU(struct pt_regs, perf_trace_regs);
extern int perf_trace_enable(int event_id);
extern void perf_trace_disable(int event_id);
extern int ftrace_profile_set_filter(struct perf_event *event, int event_id,
char *filter_str);
extern void ftrace_profile_free_filter(struct perf_event *event);
extern void *
perf_trace_buf_prepare(int size, unsigned short type, int *rctxp,
unsigned long *irq_flags);
static inline void
perf_trace_buf_submit(void *raw_data, int size, int rctx, u64 addr,
u64 count, unsigned long irq_flags, struct pt_regs *regs)
{
struct trace_entry *entry = raw_data;
perf_tp_event(entry->type, addr, count, raw_data, size, regs);
perf_swevent_put_recursion_context(rctx);
local_irq_restore(irq_flags);
}
#endif
#endif /* _LINUX_FTRACE_EVENT_H */