(trafficserver) branch master updated: Avoid Diags lock for syslog output (#13398)

[bneradt]

This is an automated email from the ASF dual-hosted git repository.

bneradt pushed a commit to branch master
in repository https://gitbox.apache.org/repos/asf/trafficserver.git


The following commit(s) were added to refs/heads/master by this push:
     new 5fc8ad3585 Avoid Diags lock for syslog output (#13398)
5fc8ad3585 is described below

commit 5fc8ad3585e267e966670743a0f20e885638ec32
Author: Brian Neradt <brian.ner...@gmail.com>
AuthorDate: Mon Jul 20 15:04:45 2026 -0500

    Avoid Diags lock for syslog output (#13398)
    
    Syslog-only diagnostics take the same mutex used to serialize file
    output, adding avoidable contention when many threads report a shared
    failure.
    
    This limits the diagnostics mutex to FILE-backed destinations and
    removes the obsolete FreeBSD exception because syslog provides its own
    thread safety.
    
    Fixes: #7374
---
 src/tscore/Diags.cc | 28 ++++++++++++++++------------
 1 file changed, 16 insertions(+), 12 deletions(-)

diff --git a/src/tscore/Diags.cc b/src/tscore/Diags.cc
index 6fe5b79cf8..a21ceb81bb 100644
--- a/src/tscore/Diags.cc
+++ b/src/tscore/Diags.cc
@@ -238,8 +238,16 @@ Diags::print_va(const char *debug_tag, DiagsLevel 
diags_level, const SourceLocat
   // now, finally, output the message //
   //////////////////////////////////////
 
-  lock();
-  if (config.outputs[diags_level].to_diagslog) {
+  auto const &output = config.outputs[diags_level];
+
+  // FILE output must be serialized, but syslog provides its own thread safety.
+  bool const serialize_file_output = output.to_diagslog || output.to_stdout || 
output.to_stderr || regression_testing_on;
+
+  if (serialize_file_output) {
+    lock();
+  }
+
+  if (output.to_diagslog) {
     if (diags_log && diags_log->m_fp) {
       va_list tmp;
       va_copy(tmp, ap);
@@ -248,7 +256,7 @@ Diags::print_va(const char *debug_tag, DiagsLevel 
diags_level, const SourceLocat
     }
   }
 
-  if (config.outputs[diags_level].to_stdout) {
+  if (output.to_stdout) {
     if (stdout_log && stdout_log->m_fp) {
       va_list tmp;
       va_copy(tmp, ap);
@@ -257,7 +265,7 @@ Diags::print_va(const char *debug_tag, DiagsLevel 
diags_level, const SourceLocat
     }
   }
 
-  if (config.outputs[diags_level].to_stderr || regression_testing_on) {
+  if (output.to_stderr || regression_testing_on) {
     if (stderr_log && stderr_log->m_fp) {
       va_list tmp;
       va_copy(tmp, ap);
@@ -266,11 +274,11 @@ Diags::print_va(const char *debug_tag, DiagsLevel 
diags_level, const SourceLocat
     }
   }
 
-#if !defined(freebsd)
-  unlock();
-#endif
+  if (serialize_file_output) {
+    unlock();
+  }
 
-  if (config.outputs[diags_level].to_syslog) {
+  if (output.to_syslog) {
     int  priority;
     char syslog_buffer[2048];
 
@@ -308,10 +316,6 @@ Diags::print_va(const char *debug_tag, DiagsLevel 
diags_level, const SourceLocat
     vsnprintf(syslog_buffer, sizeof(syslog_buffer), format_writer.data() + 
timestamp_offset, ap);
     syslog(priority, "%s", syslog_buffer);
   }
-
-#if defined(freebsd)
-  unlock();
-#endif
 }
 
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