register_trace_##name宏中
In this function, tracepoint_probe_register can hang multiple processing functions on the same cp,
View function: trace_block_rq_issue defines the hook function of this tracepoint and tracepoint
Trace_block_rq_issue(q, rq) is input to you in the tracepoint; where q is request_queue, rq is struct request, these two things are provided to you by tracepoint, all functions can be obtained, what is the execution process of this function? Yes, there must be a void function in the hook function. Each ftrace has registered its own function, including perf, which has also registered its own function in the function. Let's see what function is registered by ftrace, it must be in ftrace is to register its own specific function
There are many hook functions in kernel/trace/trace_events.c
ftrace_enable_fops
ftrace_event_format_fops
__ftrace_event_enable_disable
Using the awesome systemtap, you can easily get what the hook in the function is: call->class->reg(call, TRACE_REG_UNREGISTER, file);
The address to get the hook is: trace_event_reg
Then what is the hook function, it is found to be the function trace_event_raw_event_block_rq_issue
How did this function come about?
are generated in the header file
./include/trace/events/f2fs.h
DECLARE_EVENT_CLASS will expand the function trace_event_raw_event_block_rq_issue function in this macro
In the declare_event_class function of f2fs
122 DECLARE_EVENT_CLASS(f2fs__inode,
123
124 TP_PROTO(struct inode *inode),
125
126 TP_ARGS(inode),
127
128 TP_STRUCT__entry(
129 __field(dev_t, dev)
130 __field(ino_t, ino)
131 __field(ino_t, pino)
132 __field(umode_t, mode)
133 __field(loff_t, size)
134 __field(unsigned int, nlink)
135 __field(blkcnt_t, blocks)
136 __field(__u8, advise)
137 ),
138
139 TP_fast_assign(
140 __entry->dev = inode->i_sb->s_dev;
141 __entry->ino = inode->i_ino;
142 __entry->pino = F2FS_I(inode)->i_pino;
143 __entry->mode = inode->i_mode;
144 __entry->nlink = inode->i_nlink;
145 __entry->size = inode->i_size;
146 __entry->blocks = inode->i_blocks;
147 __entry->advise = F2FS_I(inode)->i_advise;
148 ),
149
150 TP_printk("dev = (%d,%d), ino = %lu, pino = %lu, i_mode = 0x%hx, "
151 "i_size = %lld, i_nlink = %u, i_blocks = %llu, i_advise = 0x%x",
152 show_dev_ino(__entry),
153 (unsigned long)__entry->pino,
154 __entry->mode,
155 __entry->size,
156 (unsigned int)__entry->nlink,
157 (unsigned long long)__entry->blocks,
158 (unsigned char)__entry->advise)
159 );
In the function:
./include/trace/trace_events.h
664 static notrace void \
665 trace_event_raw_event_##call(void *__data, proto) \
666 { \
667 struct trace_event_file *trace_file = __data; \
668 struct trace_event_data_offsets_##call __maybe_unused __data_offsets;\
669 struct trace_event_buffer fbuffer; \
670 struct trace_event_raw_##call *entry; \
671 int __data_size; \
672 \
673 if (trace_trigger_soft_disabled(trace_file)) \
674 return; \
675 \
676 __data_size = trace_event_get_offsets_##call(&__data_offsets, args); \
677 \
678 entry = trace_event_buffer_reserve(&fbuffer, trace_file, \
679 sizeof(*entry) + __data_size); \
680 \
681 if (!entry) \
682 return; \
683 \
684 tstruct \
685 \
686 { assign; } \
687 \
688 trace_event_buffer_commit(&fbuffer); \
689 }