Re: [RFC PATCH] perf cs-etm: Handle valid-but-zero timestamps

On 12/05/2021 05:08, Leo Yan wrote:

On Tue, May 11, 2021 at 04:53:35PM +0300, James Clark wrote:

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    /* First get the packet queue for this traceID */
    packet_queue = cs_etm__etmq_get_packet_queue(etmq, trace_chan_id);

@@ -320,7 +323,20 @@ cs_etm_decoder__do_hard_timestamp(struct cs_etm_queue *etmq, * which instructions started by subtracting the number of instructions * executed to the timestamp. */

•   packet_queue->timestamp = elem->timestamp - packet_queue->instr_count;
  

•   if (!elem->timestamp) {
  

•           packet_queue->timestamp = 0;
  

•           if (!warned_timestamp_zero) {
  

•                   pr_err("Zero Coresight timestamp found at Idx:%" OCSD_TRC_IDX_STR
  

•                           ". Decoding may be improved with --itrace=Z...\n", indx);
  

•                   warned_timestamp_zero = true;
  

•           }
  

•   }
  

•   else if (packet_queue->instr_count >= elem->timestamp) {
  

Nitpick: I personally think should use the condition ">" rather than ">=".

Yes, good catch. I actually changed this because I realised that if they are equal it shouldn't print an error.

...

•           packet_queue->timestamp = 0;
  

•           pr_err("Timestamp calculation underflow at Idx:%" OCSD_TRC_IDX_STR "\n", indx);
  

•   }
  

•   else
  

•           packet_queue->timestamp = elem->timestamp - packet_queue->instr_count;
  

Nitpick for coding style, as described in Documentation/process/coding-style.rst, section "3) Placing Braces and Spaces", so here should use braces with the format:

Ok I will update and run it through checkpatch.pl before posting.

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