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linux/kernel/trace/trace.h
Frederic Weisbecker d7350c3f45 tracing/core: make the read callbacks reentrants 
Now that several per-cpu files can be read or spliced at the
same, we want the read/splice callbacks for tracing files to be
reentrants.

Until now, a single global mutex (trace_types_lock) serialized
the access to tracing_read_pipe(), tracing_splice_read_pipe(),
and the seq helpers.

Ie: it means that if a user tries to read trace_pipe0 and
trace_pipe1 at the same time, the access to the function
tracing_read_pipe() is contended and one reader must wait for
the other to finish its read call.

The trace_type_lock mutex is mostly here to serialize the access
to the global current tracer (current_trace), which can be
changed concurrently. Although the iter struct keeps a private
pointer to this tracer, its callbacks can be changed by another
function.

The method used here is to not keep anymore private reference to
the tracer inside the iterator but to make a copy of it inside
the iterator. Then it checks on subsequents read calls if the
tracer has changed. This is not costly because the current
tracer is not expected to be changed often, so we use a branch
prediction for that.

Moreover, we add a private mutex to the iterator (there is one
iterator per file descriptor) to serialize the accesses in case
of multiple consumers per file descriptor (which would be a
silly idea from the user). Note that this is not to protect the
ring buffer, since the ring buffer already serializes the
readers accesses. This is to prevent from traces weirdness in
case of concurrent consumers. But these mutexes can be dropped
anyway, that would not result in any crash. Just tell me what
you think about it.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-02-25 13:40:58 +01:00

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#ifndef _LINUX_KERNEL_TRACE_H
#define _LINUX_KERNEL_TRACE_H
#include <linux/fs.h>
#include <asm/atomic.h>
#include <linux/sched.h>
#include <linux/clocksource.h>
#include <linux/ring_buffer.h>
#include <linux/mmiotrace.h>
#include <linux/ftrace.h>
#include <trace/boot.h>
#include <trace/kmemtrace.h>
#include <trace/power.h>
enum trace_type {
__TRACE_FIRST_TYPE = 0,
TRACE_FN,
TRACE_CTX,
TRACE_WAKE,
TRACE_STACK,
TRACE_PRINT,
TRACE_SPECIAL,
TRACE_MMIO_RW,
TRACE_MMIO_MAP,
TRACE_BRANCH,
TRACE_BOOT_CALL,
TRACE_BOOT_RET,
TRACE_GRAPH_RET,
TRACE_GRAPH_ENT,
TRACE_USER_STACK,
TRACE_HW_BRANCHES,
TRACE_KMEM_ALLOC,
TRACE_KMEM_FREE,
TRACE_POWER,
TRACE_BLK,
__TRACE_LAST_TYPE,
};
/*
* 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 char type;
unsigned char flags;
unsigned char preempt_count;
int pid;
int tgid;
};
/*
* Function trace entry - function address and parent function addres:
*/
struct ftrace_entry {
struct trace_entry ent;
unsigned long ip;
unsigned long parent_ip;
};
/* Function call entry */
struct ftrace_graph_ent_entry {
struct trace_entry ent;
struct ftrace_graph_ent graph_ent;
};
/* Function return entry */
struct ftrace_graph_ret_entry {
struct trace_entry ent;
struct ftrace_graph_ret ret;
};
extern struct tracer boot_tracer;
/*
* Context switch trace entry - which task (and prio) we switched from/to:
*/
struct ctx_switch_entry {
struct trace_entry ent;
unsigned int prev_pid;
unsigned char prev_prio;
unsigned char prev_state;
unsigned int next_pid;
unsigned char next_prio;
unsigned char next_state;
unsigned int next_cpu;
};
/*
* Special (free-form) trace entry:
*/
struct special_entry {
struct trace_entry ent;
unsigned long arg1;
unsigned long arg2;
unsigned long arg3;
};
/*
* Stack-trace entry:
*/
#define FTRACE_STACK_ENTRIES 8
struct stack_entry {
struct trace_entry ent;
unsigned long caller[FTRACE_STACK_ENTRIES];
};
struct userstack_entry {
struct trace_entry ent;
unsigned long caller[FTRACE_STACK_ENTRIES];
};
/*
* ftrace_printk entry:
*/
struct print_entry {
struct trace_entry ent;
unsigned long ip;
int depth;
char buf[];
};
#define TRACE_OLD_SIZE 88
struct trace_field_cont {
unsigned char type;
/* Temporary till we get rid of this completely */
char buf[TRACE_OLD_SIZE - 1];
};
struct trace_mmiotrace_rw {
struct trace_entry ent;
struct mmiotrace_rw rw;
};
struct trace_mmiotrace_map {
struct trace_entry ent;
struct mmiotrace_map map;
};
struct trace_boot_call {
struct trace_entry ent;
struct boot_trace_call boot_call;
};
struct trace_boot_ret {
struct trace_entry ent;
struct boot_trace_ret boot_ret;
};
#define TRACE_FUNC_SIZE 30
#define TRACE_FILE_SIZE 20
struct trace_branch {
struct trace_entry ent;
unsigned line;
char func[TRACE_FUNC_SIZE+1];
char file[TRACE_FILE_SIZE+1];
char correct;
};
struct hw_branch_entry {
struct trace_entry ent;
u64 from;
u64 to;
};
struct trace_power {
struct trace_entry ent;
struct power_trace state_data;
};
struct kmemtrace_alloc_entry {
struct trace_entry ent;
enum kmemtrace_type_id type_id;
unsigned long call_site;
const void *ptr;
size_t bytes_req;
size_t bytes_alloc;
gfp_t gfp_flags;
int node;
};
struct kmemtrace_free_entry {
struct trace_entry ent;
enum kmemtrace_type_id type_id;
unsigned long call_site;
const void *ptr;
};
/*
* trace_flag_type is an enumeration that holds different
* states when a trace occurs. These are:
* IRQS_OFF - interrupts were disabled
* IRQS_NOSUPPORT - arch does not support irqs_disabled_flags
* NEED_RESCED - reschedule is requested
* HARDIRQ - inside an interrupt handler
* SOFTIRQ - inside a softirq handler
*/
enum trace_flag_type {
TRACE_FLAG_IRQS_OFF = 0x01,
TRACE_FLAG_IRQS_NOSUPPORT = 0x02,
TRACE_FLAG_NEED_RESCHED = 0x04,
TRACE_FLAG_HARDIRQ = 0x08,
TRACE_FLAG_SOFTIRQ = 0x10,
};
#define TRACE_BUF_SIZE 1024
/*
* The CPU trace array - it consists of thousands of trace entries
* plus some other descriptor data: (for example which task started
* the trace, etc.)
*/
struct trace_array_cpu {
atomic_t disabled;
/* these fields get copied into max-trace: */
unsigned long trace_idx;
unsigned long overrun;
unsigned long saved_latency;
unsigned long critical_start;
unsigned long critical_end;
unsigned long critical_sequence;
unsigned long nice;
unsigned long policy;
unsigned long rt_priority;
cycle_t preempt_timestamp;
pid_t pid;
uid_t uid;
char comm[TASK_COMM_LEN];
};
struct trace_iterator;
/*
* The trace array - an array of per-CPU trace arrays. This is the
* highest level data structure that individual tracers deal with.
* They have on/off state as well:
*/
struct trace_array {
struct ring_buffer *buffer;
unsigned long entries;
int cpu;
cycle_t time_start;
struct task_struct *waiter;
struct trace_array_cpu *data[NR_CPUS];
};
#define FTRACE_CMP_TYPE(var, type) \
__builtin_types_compatible_p(typeof(var), type *)
#undef IF_ASSIGN
#define IF_ASSIGN(var, entry, etype, id) \
if (FTRACE_CMP_TYPE(var, etype)) { \
var = (typeof(var))(entry); \
WARN_ON(id && (entry)->type != id); \
break; \
}
/* Will cause compile errors if type is not found. */
extern void __ftrace_bad_type(void);
/*
* The trace_assign_type is a verifier that the entry type is
* the same as the type being assigned. To add new types simply
* add a line with the following format:
*
* IF_ASSIGN(var, ent, type, id);
*
* Where "type" is the trace type that includes the trace_entry
* as the "ent" item. And "id" is the trace identifier that is
* used in the trace_type enum.
*
* If the type can have more than one id, then use zero.
*/
#define trace_assign_type(var, ent) \
do { \
IF_ASSIGN(var, ent, struct ftrace_entry, TRACE_FN); \
IF_ASSIGN(var, ent, struct ctx_switch_entry, 0); \
IF_ASSIGN(var, ent, struct stack_entry, TRACE_STACK); \
IF_ASSIGN(var, ent, struct userstack_entry, TRACE_USER_STACK);\
IF_ASSIGN(var, ent, struct print_entry, TRACE_PRINT); \
IF_ASSIGN(var, ent, struct special_entry, 0); \
IF_ASSIGN(var, ent, struct trace_mmiotrace_rw, \
TRACE_MMIO_RW); \
IF_ASSIGN(var, ent, struct trace_mmiotrace_map, \
TRACE_MMIO_MAP); \
IF_ASSIGN(var, ent, struct trace_boot_call, TRACE_BOOT_CALL);\
IF_ASSIGN(var, ent, struct trace_boot_ret, TRACE_BOOT_RET);\
IF_ASSIGN(var, ent, struct trace_branch, TRACE_BRANCH); \
IF_ASSIGN(var, ent, struct ftrace_graph_ent_entry, \
TRACE_GRAPH_ENT); \
IF_ASSIGN(var, ent, struct ftrace_graph_ret_entry, \
TRACE_GRAPH_RET); \
IF_ASSIGN(var, ent, struct hw_branch_entry, TRACE_HW_BRANCHES);\
IF_ASSIGN(var, ent, struct trace_power, TRACE_POWER); \
IF_ASSIGN(var, ent, struct kmemtrace_alloc_entry, \
TRACE_KMEM_ALLOC); \
IF_ASSIGN(var, ent, struct kmemtrace_free_entry, \
TRACE_KMEM_FREE); \
__ftrace_bad_type(); \
} while (0)
/* 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 */
};
/*
* An option specific to a tracer. This is a boolean value.
* The bit is the bit index that sets its value on the
* flags value in struct tracer_flags.
*/
struct tracer_opt {
const char *name; /* Will appear on the trace_options file */
u32 bit; /* Mask assigned in val field in tracer_flags */
};
/*
* The set of specific options for a tracer. Your tracer
* have to set the initial value of the flags val.
*/
struct tracer_flags {
u32 val;
struct tracer_opt *opts;
};
/* Makes more easy to define a tracer opt */
#define TRACER_OPT(s, b) .name = #s, .bit = b
/**
* struct tracer - a specific tracer and its callbacks to interact with debugfs
* @name: the name chosen to select it on the available_tracers file
* @init: called when one switches to this tracer (echo name > current_tracer)
* @reset: called when one switches to another tracer
* @start: called when tracing is unpaused (echo 1 > tracing_enabled)
* @stop: called when tracing is paused (echo 0 > tracing_enabled)
* @open: called when the trace file is opened
* @pipe_open: called when the trace_pipe file is opened
* @wait_pipe: override how the user waits for traces on trace_pipe
* @close: called when the trace file is released
* @read: override the default read callback on trace_pipe
* @splice_read: override the default splice_read callback on trace_pipe
* @selftest: selftest to run on boot (see trace_selftest.c)
* @print_headers: override the first lines that describe your columns
* @print_line: callback that prints a trace
* @set_flag: signals one of your private flags changed (trace_options file)
* @flags: your private flags
*/
struct tracer {
const char *name;
int (*init)(struct trace_array *tr);
void (*reset)(struct trace_array *tr);
void (*start)(struct trace_array *tr);
void (*stop)(struct trace_array *tr);
void (*open)(struct trace_iterator *iter);
void (*pipe_open)(struct trace_iterator *iter);
void (*wait_pipe)(struct trace_iterator *iter);
void (*close)(struct trace_iterator *iter);
ssize_t (*read)(struct trace_iterator *iter,
struct file *filp, char __user *ubuf,
size_t cnt, loff_t *ppos);
ssize_t (*splice_read)(struct trace_iterator *iter,
struct file *filp,
loff_t *ppos,
struct pipe_inode_info *pipe,
size_t len,
unsigned int flags);
#ifdef CONFIG_FTRACE_STARTUP_TEST
int (*selftest)(struct tracer *trace,
struct trace_array *tr);
#endif
void (*print_header)(struct seq_file *m);
enum print_line_t (*print_line)(struct trace_iterator *iter);
/* If you handled the flag setting, return 0 */
int (*set_flag)(u32 old_flags, u32 bit, int set);
struct tracer *next;
int print_max;
struct tracer_flags *flags;
struct tracer_stat *stats;
};
struct trace_seq {
unsigned char buffer[PAGE_SIZE];
unsigned int len;
unsigned int readpos;
};
#define TRACE_PIPE_ALL_CPU -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];
/* The below is zeroed out in pipe_read */
struct trace_seq seq;
struct trace_entry *ent;
int cpu;
u64 ts;
unsigned long iter_flags;
loff_t pos;
long idx;
cpumask_var_t started;
};
int tracer_init(struct tracer *t, struct trace_array *tr);
int tracing_is_enabled(void);
void trace_wake_up(void);
void tracing_reset(struct trace_array *tr, int cpu);
void tracing_reset_online_cpus(struct trace_array *tr);
int tracing_open_generic(struct inode *inode, struct file *filp);
struct dentry *tracing_init_dentry(void);
void init_tracer_sysprof_debugfs(struct dentry *d_tracer);
struct ring_buffer_event;
struct ring_buffer_event *trace_buffer_lock_reserve(struct trace_array *tr,
unsigned char type,
unsigned long len,
unsigned long flags,
int pc);
void trace_buffer_unlock_commit(struct trace_array *tr,
struct ring_buffer_event *event,
unsigned long flags, int pc);
struct trace_entry *tracing_get_trace_entry(struct trace_array *tr,
struct trace_array_cpu *data);
struct trace_entry *trace_find_next_entry(struct trace_iterator *iter,
int *ent_cpu, u64 *ent_ts);
void tracing_generic_entry_update(struct trace_entry *entry,
unsigned long flags,
int pc);
void default_wait_pipe(struct trace_iterator *iter);
void poll_wait_pipe(struct trace_iterator *iter);
void ftrace(struct trace_array *tr,
struct trace_array_cpu *data,
unsigned long ip,
unsigned long parent_ip,
unsigned long flags, int pc);
void tracing_sched_switch_trace(struct trace_array *tr,
struct task_struct *prev,
struct task_struct *next,
unsigned long flags, int pc);
void tracing_record_cmdline(struct task_struct *tsk);
void tracing_sched_wakeup_trace(struct trace_array *tr,
struct task_struct *wakee,
struct task_struct *cur,
unsigned long flags, int pc);
void trace_special(struct trace_array *tr,
struct trace_array_cpu *data,
unsigned long arg1,
unsigned long arg2,
unsigned long arg3, int pc);
void trace_function(struct trace_array *tr,
unsigned long ip,
unsigned long parent_ip,
unsigned long flags, int pc);
void trace_graph_return(struct ftrace_graph_ret *trace);
int trace_graph_entry(struct ftrace_graph_ent *trace);
void tracing_start_cmdline_record(void);
void tracing_stop_cmdline_record(void);
void tracing_sched_switch_assign_trace(struct trace_array *tr);
void tracing_stop_sched_switch_record(void);
void tracing_start_sched_switch_record(void);
int register_tracer(struct tracer *type);
void unregister_tracer(struct tracer *type);
extern unsigned long nsecs_to_usecs(unsigned long nsecs);
extern unsigned long tracing_max_latency;
extern unsigned long tracing_thresh;
void update_max_tr(struct trace_array *tr, struct task_struct *tsk, int cpu);
void update_max_tr_single(struct trace_array *tr,
struct task_struct *tsk, int cpu);
void __trace_stack(struct trace_array *tr,
unsigned long flags,
int skip, int pc);
extern cycle_t ftrace_now(int cpu);
#ifdef CONFIG_CONTEXT_SWITCH_TRACER
typedef void
(*tracer_switch_func_t)(void *private,
void *__rq,
struct task_struct *prev,
struct task_struct *next);
struct tracer_switch_ops {
tracer_switch_func_t func;
void *private;
struct tracer_switch_ops *next;
};
#endif /* CONFIG_CONTEXT_SWITCH_TRACER */
extern char *trace_find_cmdline(int pid);
#ifdef CONFIG_DYNAMIC_FTRACE
extern unsigned long ftrace_update_tot_cnt;
#define DYN_FTRACE_TEST_NAME trace_selftest_dynamic_test_func
extern int DYN_FTRACE_TEST_NAME(void);
#endif
#ifdef CONFIG_FTRACE_STARTUP_TEST
extern int trace_selftest_startup_function(struct tracer *trace,
struct trace_array *tr);
extern int trace_selftest_startup_function_graph(struct tracer *trace,
struct trace_array *tr);
extern int trace_selftest_startup_irqsoff(struct tracer *trace,
struct trace_array *tr);
extern int trace_selftest_startup_preemptoff(struct tracer *trace,
struct trace_array *tr);
extern int trace_selftest_startup_preemptirqsoff(struct tracer *trace,
struct trace_array *tr);
extern int trace_selftest_startup_wakeup(struct tracer *trace,
struct trace_array *tr);
extern int trace_selftest_startup_nop(struct tracer *trace,
struct trace_array *tr);
extern int trace_selftest_startup_sched_switch(struct tracer *trace,
struct trace_array *tr);
extern int trace_selftest_startup_sysprof(struct tracer *trace,
struct trace_array *tr);
extern int trace_selftest_startup_branch(struct tracer *trace,
struct trace_array *tr);
#endif /* CONFIG_FTRACE_STARTUP_TEST */
extern void *head_page(struct trace_array_cpu *data);
extern long ns2usecs(cycle_t nsec);
extern int
trace_vprintk(unsigned long ip, int depth, const char *fmt, va_list args);
extern unsigned long trace_flags;
/* Standard output formatting function used for function return traces */
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
extern enum print_line_t print_graph_function(struct trace_iterator *iter);
#ifdef CONFIG_DYNAMIC_FTRACE
/* TODO: make this variable */
#define FTRACE_GRAPH_MAX_FUNCS 32
extern int ftrace_graph_count;
extern unsigned long ftrace_graph_funcs[FTRACE_GRAPH_MAX_FUNCS];
static inline int ftrace_graph_addr(unsigned long addr)
{
int i;
if (!ftrace_graph_count || test_tsk_trace_graph(current))
return 1;
for (i = 0; i < ftrace_graph_count; i++) {
if (addr == ftrace_graph_funcs[i])
return 1;
}
return 0;
}
#else
static inline int ftrace_trace_addr(unsigned long addr)
{
return 1;
}
static inline int ftrace_graph_addr(unsigned long addr)
{
return 1;
}
#endif /* CONFIG_DYNAMIC_FTRACE */
#else /* CONFIG_FUNCTION_GRAPH_TRACER */
static inline enum print_line_t
print_graph_function(struct trace_iterator *iter)
{
return TRACE_TYPE_UNHANDLED;
}
#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
extern struct pid *ftrace_pid_trace;
static inline int ftrace_trace_task(struct task_struct *task)
{
if (!ftrace_pid_trace)
return 1;
return test_tsk_trace_trace(task);
}
/*
* trace_iterator_flags is an enumeration that defines bit
* positions into trace_flags that controls the output.
*
* NOTE: These bits must match the trace_options array in
* trace.c.
*/
enum trace_iterator_flags {
TRACE_ITER_PRINT_PARENT = 0x01,
TRACE_ITER_SYM_OFFSET = 0x02,
TRACE_ITER_SYM_ADDR = 0x04,
TRACE_ITER_VERBOSE = 0x08,
TRACE_ITER_RAW = 0x10,
TRACE_ITER_HEX = 0x20,
TRACE_ITER_BIN = 0x40,
TRACE_ITER_BLOCK = 0x80,
TRACE_ITER_STACKTRACE = 0x100,
TRACE_ITER_SCHED_TREE = 0x200,
TRACE_ITER_PRINTK = 0x400,
TRACE_ITER_PREEMPTONLY = 0x800,
TRACE_ITER_BRANCH = 0x1000,
TRACE_ITER_ANNOTATE = 0x2000,
TRACE_ITER_USERSTACKTRACE = 0x4000,
TRACE_ITER_SYM_USEROBJ = 0x8000,
TRACE_ITER_PRINTK_MSGONLY = 0x10000,
TRACE_ITER_CONTEXT_INFO = 0x20000 /* Print pid/cpu/time */
};
/*
* TRACE_ITER_SYM_MASK masks the options in trace_flags that
* control the output of kernel symbols.
*/
#define TRACE_ITER_SYM_MASK \
(TRACE_ITER_PRINT_PARENT|TRACE_ITER_SYM_OFFSET|TRACE_ITER_SYM_ADDR)
extern struct tracer nop_trace;
/**
* ftrace_preempt_disable - disable preemption scheduler safe
*
* When tracing can happen inside the scheduler, there exists
* cases that the tracing might happen before the need_resched
* flag is checked. If this happens and the tracer calls
* preempt_enable (after a disable), a schedule might take place
* causing an infinite recursion.
*
* To prevent this, we read the need_resched flag before
* disabling preemption. When we want to enable preemption we
* check the flag, if it is set, then we call preempt_enable_no_resched.
* Otherwise, we call preempt_enable.
*
* The rational for doing the above is that if need_resched is set
* and we have yet to reschedule, we are either in an atomic location
* (where we do not need to check for scheduling) or we are inside
* the scheduler and do not want to resched.
*/
static inline int ftrace_preempt_disable(void)
{
int resched;
resched = need_resched();
preempt_disable_notrace();
return resched;
}
/**
* ftrace_preempt_enable - enable preemption scheduler safe
* @resched: the return value from ftrace_preempt_disable
*
* This is a scheduler safe way to enable preemption and not miss
* any preemption checks. The disabled saved the state of preemption.
* If resched is set, then we are either inside an atomic or
* are inside the scheduler (we would have already scheduled
* otherwise). In this case, we do not want to call normal
* preempt_enable, but preempt_enable_no_resched instead.
*/
static inline void ftrace_preempt_enable(int resched)
{
if (resched)
preempt_enable_no_resched_notrace();
else
preempt_enable_notrace();
}
#ifdef CONFIG_BRANCH_TRACER
extern int enable_branch_tracing(struct trace_array *tr);
extern void disable_branch_tracing(void);
static inline int trace_branch_enable(struct trace_array *tr)
{
if (trace_flags & TRACE_ITER_BRANCH)
return enable_branch_tracing(tr);
return 0;
}
static inline void trace_branch_disable(void)
{
/* due to races, always disable */
disable_branch_tracing();
}
#else
static inline int trace_branch_enable(struct trace_array *tr)
{
return 0;
}
static inline void trace_branch_disable(void)
{
}
#endif /* CONFIG_BRANCH_TRACER */
#endif /* _LINUX_KERNEL_TRACE_H */
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