Add TRACE() debug tracing support

This patch adds the infrastructure for the TRACE() debug macro.

Conflicts:
	kernel/printk.c

1 files changed, 53 insertions, 0 deletions

diff --git a/litmus/Kconfig b/litmus/Kconfig
index 0c7e06b922a1..e4624ee20adc 100644
--- a/litmus/Kconfig
+++ b/litmus/Kconfig
@@ -49,6 +49,59 @@ config SCHED_OVERHEAD_TRACE_SHIFT
                    24 => 512 MB
                    26 =>  2G MB
 
+config SCHED_DEBUG_TRACE
+        bool "TRACE() debugging"
+        default n
+        help
+          Include support for sched_trace_log_messageg(), which is used to
+          implement TRACE(). If disabled, no TRACE() messages will be included
+          in the kernel, and no overheads due to debugging statements will be
+          incurred by the scheduler. Disable if the overhead is not acceptable
+          (e.g. benchmarking).
+
+          Say Yes for debugging.
+          Say No for overhead tracing.
+
+config SCHED_DEBUG_TRACE_SHIFT
+       int "Buffer size for TRACE() buffer"
+       depends on SCHED_DEBUG_TRACE
+       range 14 22
+       default 18
+       help
+
+        Select the amount of memory needed per for the TRACE() buffer, as a
+        power of two. The TRACE() buffer is global and statically allocated. If
+        the buffer is too small, there will be holes in the TRACE() log if the
+        buffer-flushing task is starved.
+
+        The default should be sufficient for most systems. Increase the buffer
+        size if the log contains holes. Reduce the buffer size when running on
+        a memory-constrained system.
+
+        Examples: 14 =>  16KB
+                  18 => 256KB
+                  20 =>   1MB
+
+        This buffer is exported to usespace using a misc device as
+        'litmus/log'. On a system with default udev rules, a corresponding
+        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