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https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
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e7c15cd8a1
The hardware latency tracer has been in the PREEMPT_RT patch for some time.
It is used to detect possible SMIs or any other hardware interruptions that
the kernel is unaware of. Note, NMIs may also be detected, but that may be
good to note as well.
The logic is pretty simple. It simply creates a thread that spins on a
single CPU for a specified amount of time (width) within a periodic window
(window). These numbers may be adjusted by their cooresponding names in
/sys/kernel/tracing/hwlat_detector/
The defaults are window = 1000000 us (1 second)
width = 500000 us (1/2 second)
The loop consists of:
t1 = trace_clock_local();
t2 = trace_clock_local();
Where trace_clock_local() is a variant of sched_clock().
The difference of t2 - t1 is recorded as the "inner" timestamp and also the
timestamp t1 - prev_t2 is recorded as the "outer" timestamp. If either of
these differences are greater than the time denoted in
/sys/kernel/tracing/tracing_thresh then it records the event.
When this tracer is started, and tracing_thresh is zero, it changes to the
default threshold of 10 us.
The hwlat tracer in the PREEMPT_RT patch was originally written by
Jon Masters. I have modified it quite a bit and turned it into a
tracer.
Based-on-code-by: Jon Masters <jcm@redhat.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
347 lines
7.9 KiB
C
347 lines
7.9 KiB
C
/*
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* This file defines the trace event structures that go into the ring
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* buffer directly. They are created via macros so that changes for them
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* appear in the format file. Using macros will automate this process.
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*
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* The macro used to create a ftrace data structure is:
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*
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* FTRACE_ENTRY( name, struct_name, id, structure, print )
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*
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* @name: the name used the event name, as well as the name of
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* the directory that holds the format file.
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*
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* @struct_name: the name of the structure that is created.
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*
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* @id: The event identifier that is used to detect what event
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* this is from the ring buffer.
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*
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* @structure: the structure layout
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*
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* - __field( type, item )
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* This is equivalent to declaring
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* type item;
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* in the structure.
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* - __array( type, item, size )
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* This is equivalent to declaring
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* type item[size];
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* in the structure.
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*
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* * for structures within structures, the format of the internal
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* structure is laid out. This allows the internal structure
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* to be deciphered for the format file. Although these macros
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* may become out of sync with the internal structure, they
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* will create a compile error if it happens. Since the
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* internel structures are just tracing helpers, this is not
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* an issue.
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*
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* When an internal structure is used, it should use:
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*
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* __field_struct( type, item )
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*
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* instead of __field. This will prevent it from being shown in
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* the output file. The fields in the structure should use.
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*
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* __field_desc( type, container, item )
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* __array_desc( type, container, item, len )
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*
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* type, item and len are the same as __field and __array, but
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* container is added. This is the name of the item in
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* __field_struct that this is describing.
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*
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*
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* @print: the print format shown to users in the format file.
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*/
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/*
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* Function trace entry - function address and parent function address:
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*/
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FTRACE_ENTRY_REG(function, ftrace_entry,
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TRACE_FN,
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F_STRUCT(
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__field( unsigned long, ip )
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__field( unsigned long, parent_ip )
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),
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F_printk(" %lx <-- %lx", __entry->ip, __entry->parent_ip),
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FILTER_TRACE_FN,
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perf_ftrace_event_register
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);
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/* Function call entry */
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FTRACE_ENTRY_PACKED(funcgraph_entry, ftrace_graph_ent_entry,
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TRACE_GRAPH_ENT,
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F_STRUCT(
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__field_struct( struct ftrace_graph_ent, graph_ent )
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__field_desc( unsigned long, graph_ent, func )
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__field_desc( int, graph_ent, depth )
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),
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F_printk("--> %lx (%d)", __entry->func, __entry->depth),
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FILTER_OTHER
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);
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/* Function return entry */
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FTRACE_ENTRY_PACKED(funcgraph_exit, ftrace_graph_ret_entry,
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TRACE_GRAPH_RET,
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F_STRUCT(
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__field_struct( struct ftrace_graph_ret, ret )
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__field_desc( unsigned long, ret, func )
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__field_desc( unsigned long long, ret, calltime)
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__field_desc( unsigned long long, ret, rettime )
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__field_desc( unsigned long, ret, overrun )
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__field_desc( int, ret, depth )
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),
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F_printk("<-- %lx (%d) (start: %llx end: %llx) over: %d",
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__entry->func, __entry->depth,
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__entry->calltime, __entry->rettime,
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__entry->depth),
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FILTER_OTHER
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);
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/*
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* Context switch trace entry - which task (and prio) we switched from/to:
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*
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* This is used for both wakeup and context switches. We only want
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* to create one structure, but we need two outputs for it.
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*/
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#define FTRACE_CTX_FIELDS \
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__field( unsigned int, prev_pid ) \
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__field( unsigned int, next_pid ) \
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__field( unsigned int, next_cpu ) \
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__field( unsigned char, prev_prio ) \
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__field( unsigned char, prev_state ) \
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__field( unsigned char, next_prio ) \
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__field( unsigned char, next_state )
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FTRACE_ENTRY(context_switch, ctx_switch_entry,
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TRACE_CTX,
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F_STRUCT(
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FTRACE_CTX_FIELDS
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),
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F_printk("%u:%u:%u ==> %u:%u:%u [%03u]",
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__entry->prev_pid, __entry->prev_prio, __entry->prev_state,
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__entry->next_pid, __entry->next_prio, __entry->next_state,
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__entry->next_cpu),
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FILTER_OTHER
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);
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/*
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* FTRACE_ENTRY_DUP only creates the format file, it will not
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* create another structure.
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*/
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FTRACE_ENTRY_DUP(wakeup, ctx_switch_entry,
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TRACE_WAKE,
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F_STRUCT(
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FTRACE_CTX_FIELDS
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),
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F_printk("%u:%u:%u ==+ %u:%u:%u [%03u]",
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__entry->prev_pid, __entry->prev_prio, __entry->prev_state,
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__entry->next_pid, __entry->next_prio, __entry->next_state,
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__entry->next_cpu),
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FILTER_OTHER
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);
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/*
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* Stack-trace entry:
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*/
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#define FTRACE_STACK_ENTRIES 8
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#ifndef CONFIG_64BIT
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# define IP_FMT "%08lx"
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#else
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# define IP_FMT "%016lx"
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#endif
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FTRACE_ENTRY(kernel_stack, stack_entry,
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TRACE_STACK,
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F_STRUCT(
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__field( int, size )
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__dynamic_array(unsigned long, caller )
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),
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F_printk("\t=> (" IP_FMT ")\n\t=> (" IP_FMT ")\n\t=> (" IP_FMT ")\n"
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"\t=> (" IP_FMT ")\n\t=> (" IP_FMT ")\n\t=> (" IP_FMT ")\n"
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"\t=> (" IP_FMT ")\n\t=> (" IP_FMT ")\n",
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__entry->caller[0], __entry->caller[1], __entry->caller[2],
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__entry->caller[3], __entry->caller[4], __entry->caller[5],
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__entry->caller[6], __entry->caller[7]),
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FILTER_OTHER
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);
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FTRACE_ENTRY(user_stack, userstack_entry,
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TRACE_USER_STACK,
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F_STRUCT(
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__field( unsigned int, tgid )
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__array( unsigned long, caller, FTRACE_STACK_ENTRIES )
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),
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F_printk("\t=> (" IP_FMT ")\n\t=> (" IP_FMT ")\n\t=> (" IP_FMT ")\n"
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"\t=> (" IP_FMT ")\n\t=> (" IP_FMT ")\n\t=> (" IP_FMT ")\n"
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"\t=> (" IP_FMT ")\n\t=> (" IP_FMT ")\n",
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__entry->caller[0], __entry->caller[1], __entry->caller[2],
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__entry->caller[3], __entry->caller[4], __entry->caller[5],
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__entry->caller[6], __entry->caller[7]),
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FILTER_OTHER
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);
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/*
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* trace_printk entry:
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*/
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FTRACE_ENTRY(bprint, bprint_entry,
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TRACE_BPRINT,
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F_STRUCT(
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__field( unsigned long, ip )
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__field( const char *, fmt )
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__dynamic_array( u32, buf )
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),
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F_printk("%ps: %s",
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(void *)__entry->ip, __entry->fmt),
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FILTER_OTHER
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);
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FTRACE_ENTRY(print, print_entry,
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TRACE_PRINT,
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F_STRUCT(
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__field( unsigned long, ip )
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__dynamic_array( char, buf )
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),
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F_printk("%ps: %s",
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(void *)__entry->ip, __entry->buf),
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FILTER_OTHER
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);
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FTRACE_ENTRY(bputs, bputs_entry,
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TRACE_BPUTS,
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F_STRUCT(
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__field( unsigned long, ip )
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__field( const char *, str )
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),
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F_printk("%ps: %s",
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(void *)__entry->ip, __entry->str),
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FILTER_OTHER
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);
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FTRACE_ENTRY(mmiotrace_rw, trace_mmiotrace_rw,
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TRACE_MMIO_RW,
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F_STRUCT(
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__field_struct( struct mmiotrace_rw, rw )
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__field_desc( resource_size_t, rw, phys )
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__field_desc( unsigned long, rw, value )
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__field_desc( unsigned long, rw, pc )
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__field_desc( int, rw, map_id )
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__field_desc( unsigned char, rw, opcode )
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__field_desc( unsigned char, rw, width )
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),
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F_printk("%lx %lx %lx %d %x %x",
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(unsigned long)__entry->phys, __entry->value, __entry->pc,
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__entry->map_id, __entry->opcode, __entry->width),
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FILTER_OTHER
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);
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FTRACE_ENTRY(mmiotrace_map, trace_mmiotrace_map,
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TRACE_MMIO_MAP,
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F_STRUCT(
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__field_struct( struct mmiotrace_map, map )
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__field_desc( resource_size_t, map, phys )
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__field_desc( unsigned long, map, virt )
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__field_desc( unsigned long, map, len )
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__field_desc( int, map, map_id )
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__field_desc( unsigned char, map, opcode )
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),
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F_printk("%lx %lx %lx %d %x",
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(unsigned long)__entry->phys, __entry->virt, __entry->len,
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__entry->map_id, __entry->opcode),
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FILTER_OTHER
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);
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#define TRACE_FUNC_SIZE 30
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#define TRACE_FILE_SIZE 20
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FTRACE_ENTRY(branch, trace_branch,
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TRACE_BRANCH,
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F_STRUCT(
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__field( unsigned int, line )
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__array( char, func, TRACE_FUNC_SIZE+1 )
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__array( char, file, TRACE_FILE_SIZE+1 )
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__field( char, correct )
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),
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F_printk("%u:%s:%s (%u)",
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__entry->line,
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__entry->func, __entry->file, __entry->correct),
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FILTER_OTHER
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);
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FTRACE_ENTRY(hwlat, hwlat_entry,
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TRACE_HWLAT,
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F_STRUCT(
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__field( u64, duration )
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__field( u64, outer_duration )
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__field_struct( struct timespec, timestamp )
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__field_desc( long, timestamp, tv_sec )
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__field_desc( long, timestamp, tv_nsec )
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__field( unsigned int, seqnum )
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),
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F_printk("cnt:%u\tts:%010lu.%010lu\tinner:%llu\touter:%llu\n",
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__entry->seqnum,
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__entry->tv_sec,
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__entry->tv_nsec,
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__entry->duration,
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__entry->outer_duration),
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FILTER_OTHER
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);
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