add optional [function@file:line] tag to TRACE() log

Add information to each trace message that makes it easier to locate
where it came from. It is disabled by default since this adds a lot of
clutter. Example:

  81281 P1 [gsnedf_schedule@litmus/sched_gsn_edf.c:406]: (rtspin/1483:1) blocks:0 out_of_time:0 np:0 sleep:1 preempt:0 state:0 sig:0
  81282 P1 [job_completion@litmus/sched_gsn_edf.c:303]: (rtspin/1483:1) job_completion().
  81283 P1 [__add_release@litmus/rt_domain.c:344]: (rtspin/1483:2) add_release(), rel=41941764351
  81284 P1 [gsnedf_schedule@litmus/sched_gsn_edf.c:453]: (rtspin/1483:2) scheduled_on = NO_CPU

2 files changed, 28 insertions, 3 deletions

diff --git a/include/litmus/debug_trace.h b/include/litmus/debug_trace.h
index 2e946f147ca7..48d086d5a44c 100644
--- a/include/litmus/debug_trace.h
+++ b/include/litmus/debug_trace.h
@@ -12,10 +12,20 @@ void dump_trace_buffer(int max);
 
 extern atomic_t __log_seq_no;
 
+#ifdef CONFIG_SCHED_DEBUG_TRACE_CALLER
+#define TRACE_PREFIX "%d P%d [%s@%s:%d]: "
+#define TRACE_ARGS  atomic_add_return(1, &__log_seq_no),        \
+                raw_smp_processor_id(),                         \
+                __FUNCTION__, __FILE__, __LINE__
+#else
+#define TRACE_PREFIX "%d P%d: "
+#define TRACE_ARGS  atomic_add_return(1, &__log_seq_no), \
+                raw_smp_processor_id()
+#endif
+
 #define TRACE(fmt, args...)                                             \
-        sched_trace_log_message("%d P%d: " fmt,                         \
-                                atomic_add_return(1, &__log_seq_no),    \
-                                raw_smp_processor_id(), ## args)
+        sched_trace_log_message(TRACE_PREFIX fmt,                       \
+                                TRACE_ARGS,  ## args)
 
 #define TRACE_TASK(t, fmt, args...)                     \
         TRACE("(%s/%d:%d) " fmt, (t)->comm, (t)->pid,   \
diff --git a/litmus/Kconfig b/litmus/Kconfig
index d62c417f261e..a2f267870f29 100644
--- a/litmus/Kconfig
+++ b/litmus/Kconfig
@@ -174,6 +174,21 @@ config SCHED_DEBUG_TRACE_SHIFT
         character device node should be created at /dev/litmus/log. The buffer
         can be flushed using cat, e.g., 'cat /dev/litmus/log > my_log_file.txt'.
 
+config SCHED_DEBUG_TRACE_CALLER
+       bool "Include [function@file:line] tag in TRACE() log"
+       depends on SCHED_DEBUG_TRACE
+       default n
+       help
+         With this option enabled, TRACE() prepends
+
+              "[<function name>@<filename>:<line number>]"
+
+         to each message in the debug log. Enable this to aid in figuring out
+         what was called in which order. The downside is that it adds a lot of
+         clutter.
+
+         If unsure, say No.
+
 endmenu
 
 endmenu