[PATCH 1/2] rteval: Add -L/--logging support to timerlat measurement module

This implements file logging for the timerlat measurement module, matching
the functionality available in load modules like hackbench and kcompile.

When rteval is run with the -L/--logging flag, timerlat will now save
rtla timerlat's stdout and stderr to files in workdir/logs/:
- timerlat.stdout - raw output from rtla timerlat hist
- timerlat.stderr - any error messages from rtla

This is useful for:
- Debugging new rtla versions with different output formats
- Investigating parsing issues
- Understanding rtla behavior when things go wrong

Changes:
- Add _logging config flag (default: False)
- Add __reportdir config to locate logs directory
- Add __open_logfile() helper method (uses O_RDWR to support read+write)
- Conditionally use real log files vs temp files in _WorkloadPrepare()
- Handle reading from both file descriptors and temp files in _WorkloadCleanup()
- Close files appropriately based on type (os.close vs .close())
- Conditional seek only for temp files (file descriptors start at position 0)

Assisted-by: Claude:claude-sonnet-4-5
Signed-off-by: John Kacur <[email protected]>
---
 rteval/modules/measurement/timerlat.py | 54 +++++++++++++++++++++-----
 1 file changed, 45 insertions(+), 9 deletions(-)

diff --git a/rteval/modules/measurement/timerlat.py b/rteval/modules/measurement/timerlat.py
index 2172f6ece520..03faa08639d5 100644
--- a/rteval/modules/measurement/timerlat.py
+++ b/rteval/modules/measurement/timerlat.py
@@ -189,6 +189,10 @@ class Timerlat(rtevalModulePrototype):
         self.__cpus = [str(c) for c in expand_cpulist(self.__cpulist)]
         self.__numcores = len(self.__cpus)
 
+        # Logging configuration
+        self._logging = self.__cfg.setdefault('logging', False)
+        self.__reportdir = self.__cfg.setdefault('reportdir', os.getcwd())
+
         # Has tracing been triggered
         self.__stoptrace = False
         # This stores the output from rtla
@@ -218,6 +222,12 @@ class Timerlat(rtevalModulePrototype):
         self._log(Log.DEBUG, f"system using {self.__numcores} cpu cores")
         self.set_latency_test()
 
+    def __open_logfile(self, name):
+        """Open a log file in the reportdir/logs directory"""
+        logdir = os.path.join(self.__reportdir, "logs")
+        if not os.path.exists(logdir):
+            os.makedirs(logdir)
+        return os.open(os.path.join(logdir, name), os.O_CREAT|os.O_RDWR|os.O_TRUNC)
 
     def _WorkloadSetup(self):
         self.__timerlat_process = None
@@ -250,8 +260,14 @@ class Timerlat(rtevalModulePrototype):
                 self.__cmd.append(f'-t={self.__cfg.trace}')
 
         self._log(Log.DEBUG, f'self.__cmd = {self.__cmd}')
-        self.__timerlat_out = tempfile.SpooledTemporaryFile(mode='w+b')
-        self.__timerlat_err = tempfile.SpooledTemporaryFile(mode='w+b')
+
+        # Setup output files - use actual log files if logging enabled, otherwise temp files
+        if self._logging:
+            self.__timerlat_out = self.__open_logfile("timerlat.stdout")
+            self.__timerlat_err = self.__open_logfile("timerlat.stderr")
+        else:
+            self.__timerlat_out = tempfile.SpooledTemporaryFile(mode='w+b')
+            self.__timerlat_err = tempfile.SpooledTemporaryFile(mode='w+b')
 
 
     def _WorkloadTask(self):
@@ -260,8 +276,11 @@ class Timerlat(rtevalModulePrototype):
 
         self._log(Log.DEBUG, f'starting with cmd: {" ".join(self.__cmd)}')
 
-        self.__timerlat_out.seek(0)
-        self.__timerlat_err.seek(0)
+        # Seek to beginning - only needed for temp files, file descriptors start at position 0
+        if not self._logging:
+            self.__timerlat_out.seek(0)
+            self.__timerlat_err.seek(0)
+
         self.__timerlat_process = subprocess.Popen(self.__cmd,
                                                    stdout=self.__timerlat_out,
                                                    stderr=self.__timerlat_err,
@@ -308,14 +327,26 @@ class Timerlat(rtevalModulePrototype):
         # Parse histogram output - use try/finally to ensure _setFinished() is always called
         # This prevents hangs if parsing fails due to partial output (RHEL-140898)
         try:
-            self.__timerlat_out.seek(0)
+            # Read output - handle both file descriptors and temp files
+            if self._logging:
+                # For file descriptors, read the entire file content
+                os.lseek(self.__timerlat_out, 0, os.SEEK_SET)
+                output_data = os.read(self.__timerlat_out, 10*1024*1024)  # Read up to 10MB
+                output_lines = output_data.decode('utf-8', errors='replace').splitlines(keepends=True)
+            else:
+                # For temp files, use seek and iterate
+                self.__timerlat_out.seek(0)
+                output_lines = self.__timerlat_out
 
             blocking_thread_detected = False
             softirq_interference_detected = False
             irq_interference_detected = False
 
-            for line in self.__timerlat_out:
-                line = bytes.decode(line)
+            for line in output_lines:
+                if isinstance(line, bytes):
+                    line = bytes.decode(line)
+                elif not isinstance(line, str):
+                    line = str(line)
 
                 # Skip any blank lines
                 if not line:
@@ -474,8 +505,13 @@ class Timerlat(rtevalModulePrototype):
             self._setFinished()
             self.__started = False
 
-            self.__timerlat_err.close()
-            self.__timerlat_out.close()
+            # Close output files - method differs for file descriptors vs temp files
+            if self._logging:
+                os.close(self.__timerlat_out)
+                os.close(self.__timerlat_err)
+            else:
+                self.__timerlat_out.close()
+                self.__timerlat_err.close()
 
     def MakeReport(self):
         rep_n = libxml2.newNode('timerlat')
-- 
2.54.0