Messages in this thread | ![/](/images/icornerl.gif) | | Date | Thu, 15 Dec 2022 09:22:59 +0800 | Subject | Re: [RFC PATCH 2/2] trace: allocate temparary buffer for trace output usage | From | Linyu Yuan <> |
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thanks for remind, will check and use it.
thanks
On 12/14/2022 10:25 PM, Steven Rostedt wrote: > On Wed, 14 Dec 2022 22:11:42 +0800 > Linyu Yuan <quic_linyyuan@quicinc.com> wrote: > >> there is one dwc3 trace event declare as below, >> DECLARE_EVENT_CLASS(dwc3_log_event, >> TP_PROTO(u32 event, struct dwc3 *dwc), >> TP_ARGS(event, dwc), >> TP_STRUCT__entry( >> __field(u32, event) >> __field(u32, ep0state) >> __dynamic_array(char, str, DWC3_MSG_MAX) >> ), >> TP_fast_assign( >> __entry->event = event; >> __entry->ep0state = dwc->ep0state; >> ), >> TP_printk("event (%08x): %s", __entry->event, >> dwc3_decode_event(__get_str(str), DWC3_MSG_MAX, >> __entry->event, __entry->ep0state)) >> ); >> the problem is when trace function called, it will allocate up to >> DWC3_MSG_MAX bytes from trace event buffer, but never fill the buffer >> during fast assignment, it only fill the buffer when output function are >> called, so this means if output function are not called, the buffer will >> never used. >> >> add __alloc_buf() and __get_buf() which will not allocate event buffer >> when trace function called, but when trace output function called, it will >> kmalloc buffer with size DWC3_MSG_MAX for temprary usage and free it >> before trace output function return. > This looks exactly like what the trace_seq *p is to be used for. > > static notrace enum print_line_t \ > trace_raw_output_##call(struct trace_iterator *iter, int flags, \ > struct trace_event *trace_event) \ > { \ > struct trace_seq *s = &iter->seq; \ > struct trace_seq __maybe_unused *p = &iter->tmp_seq; \ > ^^^^^^^^^^^^^^^^^^^^ > > struct trace_event_raw_##call *field; \ > int ret; \ > \ > field = (typeof(field))iter->ent; \ > \ > ret = trace_raw_output_prep(iter, trace_event); \ > if (ret != TRACE_TYPE_HANDLED) \ > return ret; \ > \ > trace_event_printf(iter, print); \ > \ > return trace_handle_return(s); \ > } \ > > That is a trace_seq buffer that is for temporary usage during the output. > > See: > include/trace/events/libata.h > include/trace/events/scsi.h > > As well as the macros trace_print_bitmask_seq(), trace_print_flags_seq(), > trace_print_symbols_seq(), etc. > > -- Steve >
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