From b0bbd261455dd9cdb5575610d5fe8a3975289ed8 Mon Sep 17 00:00:00 2001
From: Mihai Carabas <mihai.carabas@gmail.com>
Date: Wed, 22 Aug 2012 13:07:18 +0000
Subject: [PATCH] ktr - add KTR_COND_LOG

 * KTR_COND_LOG provides conditional logging; the second parameter passed
   in is a condition which determines whether the entry is logged or
   not.

 * It provides a neater way to log conditionally than having to wrap a
   KTR in an if, which may then end up being empty if KTR is disbled.
---
 share/man/man9/ktr.9 | 22 ++++++++++++++++++++--
 sys/sys/ktr.h        | 21 +++++++++++++++++++++
 2 files changed, 41 insertions(+), 2 deletions(-)

diff --git a/share/man/man9/ktr.9 b/share/man/man9/ktr.9
index 9c72cdf51d..c15f672029 100644
--- a/share/man/man9/ktr.9
+++ b/share/man/man9/ktr.9
@@ -24,14 +24,15 @@
 .\"
 .\" $FreeBSD: src/share/man/man9/ktr.9,v 1.8 2005/03/08 01:37:36 hmp Exp $
 .\"
-.Dd January 2, 2012
+.Dd August 22, 2012
 .Dt KTR 9
 .Os
 .Sh NAME
 .Nm KTR_INFO_MASTER ,
 .Nm KTR_INFO_MASTER_EXTERN ,
 .Nm KTR_INFO ,
-.Nm KTR_LOG
+.Nm KTR_LOG ,
+.Nm KTR_COND_LOG
 .Nd kernel tracing facility
 .Sh SYNOPSIS
 .In sys/ktr.h
@@ -42,6 +43,7 @@
 .Fn KTR_INFO_MASTER_EXTERN "master"
 .Fn KTR_INFO "compile" "master" "name" "maskbit" "format" "type name" "..."
 .Fn KTR_LOG "info" "arg ..."
+.Fn KTR_COND_LOG "info" "cond" "arg ..."
 .Sh DESCRIPTION
 The
 .Nm ktr
@@ -104,6 +106,14 @@ string passed to the associated
 call.
 .Pp
 The
+.Fn KTR_COND_LOG
+macro is equivalent to
+.Fn KTR_LOG
+except it logs only when the condition specified in
+.Fa cond
+evaluates to true.
+.Pp
+The
 .Va ktr_entries
 variable contains the number of entries in the
 .Va ktr_buf
@@ -129,6 +139,7 @@ This example demonstrates a simple usage of the KTR facility:
 KTR_INFO_MASTER(foo);
 KTR_INFO(KTR_FOO, foo, func1, 0, "func1()");
 KTR_INFO(KTR_FOO, foo, func2, 1, "func2(%d)", int arg);
+KTR_INFO(KTR_FOO, foo, func3, 2, "func3: arg positive: %d", int arg);
 
 \&...
 
@@ -145,6 +156,13 @@ func2(int arg)
 	KTR_LOG(foo_func2, arg);
 	...
 }
+
+void
+func3(int arg)
+{
+	KTR_COND_LOG(foo_func3, arg >= 0, arg);
+	...
+}
 .Ed
 .Sh SEE ALSO
 .Xr gdb 1 ,
diff --git a/sys/sys/ktr.h b/sys/sys/ktr.h
index 8becde37ef..7b32bee932 100644
--- a/sys/sys/ktr.h
+++ b/sys/sys/ktr.h
@@ -197,6 +197,25 @@ SYSCTL_DECL(_debug_ktr);
 		}							\
 	}  while(0)
 
+#define KTR_COND_LOG(name, cond, ...)					\
+	do {								\
+		__ktr_info_ ## name ## _fmtcheck (__ktr_ ## name ## _fmt, ##__VA_ARGS__);	\
+		if ((cond) &&						\
+		    ktr_ ## name ## _enable &&				\
+		    (ktr_ ## name ## _mask & *ktr_info_ ## name .kf_master_enable)) { \
+			struct ktr_entry *entry;			\
+			entry = ktr_begin_write_entry(&ktr_info_ ## name, __FILE__, __LINE__); \
+			if (!entry)					\
+				break;					\
+			*(struct ktr_info_  ## name ## _args *)&entry->ktr_data[0] = \
+				(struct ktr_info_  ## name ## _args){ __VA_ARGS__}; \
+			if (ktr_finish_write_entry(&ktr_info_ ## name, entry)) { \
+				kprintf(ktr_info_ ## name .kf_format, ##__VA_ARGS__); \
+				kprintf("\n");				\
+			}						\
+		}							\
+	}  while(0)
+
 #else
 
 #define KTR_INFO_MASTER(master)						\
@@ -211,6 +230,8 @@ SYSCTL_DECL(_debug_ktr);
 
 #define KTR_LOG(info, args...)
 
+#define KTR_COND_LOG(info, args...)
+
 #endif
 
 #endif /* !LOCORE */
-- 
2.41.0