From b0161972b61f32e3939b1d00ed596a51f2d9df53 Mon Sep 17 00:00:00 2001
From: kib <kib@FreeBSD.org>
Date: Wed, 18 Jul 2018 09:54:32 +0000
Subject: [PATCH] MFC r335939, r336088: Add setproctitle_fast(3) for frequent
 callers.

---
 include/unistd.h            |  1 +
 lib/libc/gen/Symbol.map     |  1 +
 lib/libc/gen/setproctitle.3 | 14 ++++++-
 lib/libc/gen/setproctitle.c | 75 +++++++++++++++++++++++++++----------
 4 files changed, 70 insertions(+), 21 deletions(-)

diff --git a/include/unistd.h b/include/unistd.h
index fc310646654..c91fd592c21 100644
--- a/include/unistd.h
+++ b/include/unistd.h
@@ -569,6 +569,7 @@ int	 setloginclass(const char *);
 void	*setmode(const char *);
 int	 setpgrp(pid_t, pid_t);			/* obsoleted by setpgid() */
 void	 setproctitle(const char *_fmt, ...) __printf0like(1, 2);
+void	 setproctitle_fast(const char *_fmt, ...) __printf0like(1, 2);
 int	 setresgid(gid_t, gid_t, gid_t);
 int	 setresuid(uid_t, uid_t, uid_t);
 int	 setrgid(gid_t);
diff --git a/lib/libc/gen/Symbol.map b/lib/libc/gen/Symbol.map
index cb4e4da69fc..56e1006f2b5 100644
--- a/lib/libc/gen/Symbol.map
+++ b/lib/libc/gen/Symbol.map
@@ -420,6 +420,7 @@ FBSD_1.4 {
 
 FBSD_1.5 {
 	sem_clockwait_np;
+	setproctitle_fast;
 };
 
 FBSDprivate_1.0 {
diff --git a/lib/libc/gen/setproctitle.3 b/lib/libc/gen/setproctitle.3
index 955556e5b20..af8e885b5d0 100644
--- a/lib/libc/gen/setproctitle.3
+++ b/lib/libc/gen/setproctitle.3
@@ -20,7 +20,7 @@
 .\" $FreeBSD$
 .\"
 .\" The following requests are required for all man pages.
-.Dd December 16, 1995
+.Dd July 4, 2018
 .Dt SETPROCTITLE 3
 .Os
 .Sh NAME
@@ -31,12 +31,20 @@
 .In unistd.h
 .Ft void
 .Fn setproctitle "const char *fmt" "..."
+.Ft void
+.Fn setproctitle_fast "const char *fmt" "..."
 .Sh DESCRIPTION
 The
 .Fn setproctitle
 library routine sets the process title that appears on the
 .Xr ps 1
 command.
+The
+.Fn setproctitle_fast
+variant is optimized for high frequency updates, but may make the
+.Xr ps 1
+command slightly slower by not updating the kernel cache of the program
+arguments.
 .Pp
 The title is set from the executable's name, followed by the
 result of a
@@ -96,6 +104,10 @@ The
 function
 first appeared in
 .Fx 2.2 .
+The
+.Fn setproctitle_fast
+function first appeared in
+.Fx 12 .
 Other operating systems have
 similar functions.
 .Sh AUTHORS
diff --git a/lib/libc/gen/setproctitle.c b/lib/libc/gen/setproctitle.c
index fd87c350715..a631c70e1e9 100644
--- a/lib/libc/gen/setproctitle.c
+++ b/lib/libc/gen/setproctitle.c
@@ -55,8 +55,8 @@ struct old_ps_strings {
 
 #define SPT_BUFSIZE 2048	/* from other parts of sendmail */
 
-void
-setproctitle(const char *fmt, ...)
+static char *
+setproctitle_internal(const char *fmt, va_list ap)
 {
 	static struct ps_strings *ps_strings;
 	static char *buf = NULL;
@@ -67,27 +67,23 @@ setproctitle(const char *fmt, ...)
 	char **nargvp;
 	int nargc;
 	int i;
-	va_list ap;
 	size_t len;
 	unsigned long ul_ps_strings;
-	int oid[4];
 
 	if (buf == NULL) {
 		buf = malloc(SPT_BUFSIZE);
 		if (buf == NULL) 
-			return;
+			return (NULL);
 		nargv[0] = buf;
 	}
 
 	if (obuf == NULL ) {
 		obuf = malloc(SPT_BUFSIZE);
 		if (obuf == NULL)
-			return;
+			return (NULL);
 		*obuf = '\0';
 	}
 
-	va_start(ap, fmt);
-
 	if (fmt) {
 		buf[SPT_BUFSIZE - 1] = '\0';
 
@@ -114,22 +110,13 @@ setproctitle(const char *fmt, ...)
 		kbuf = obuf;
 	} else
 		/* Nothing to restore */
-		return;
-
-	va_end(ap);
-
-	/* Set the title into the kernel cached command line */
-	oid[0] = CTL_KERN;
-	oid[1] = KERN_PROC;
-	oid[2] = KERN_PROC_ARGS;
-	oid[3] = getpid();
-	sysctl(oid, 4, 0, 0, kbuf, strlen(kbuf) + 1);
+		return (NULL);
 
 	if (ps_strings == NULL) {
 		len = sizeof(ul_ps_strings);
 		if (sysctlbyname("kern.ps_strings", &ul_ps_strings, &len, NULL,
 		    0) == -1)
-			return;
+			return (NULL);
 		ps_strings = (struct ps_strings *)ul_ps_strings;
 	}
 
@@ -138,7 +125,7 @@ setproctitle(const char *fmt, ...)
 	 * Should not happen.
 	 */
 	if (ps_strings->ps_argvstr == NULL)
-		return;
+		return (NULL);
 
 	/* style #3 */
 	if (oargc == -1) {
@@ -167,4 +154,52 @@ setproctitle(const char *fmt, ...)
 	}
 	ps_strings->ps_nargvstr = nargc;
 	ps_strings->ps_argvstr = nargvp;
+
+	return (nargvp[0]);
+}
+
+static int fast_update = 0;
+
+void
+setproctitle_fast(const char *fmt, ...)
+{
+	va_list ap;
+	char *buf;
+	int oid[4];
+
+	va_start(ap, fmt);
+	buf = setproctitle_internal(fmt, ap);
+	va_end(ap);
+
+	if (buf && !fast_update) {
+		/* Tell the kernel to start looking in user-space */
+		oid[0] = CTL_KERN;
+		oid[1] = KERN_PROC;
+		oid[2] = KERN_PROC_ARGS;
+		oid[3] = getpid();
+		sysctl(oid, 4, 0, 0, "", 0);
+		fast_update = 1;
+	}
+}
+
+void
+setproctitle(const char *fmt, ...)
+{
+	va_list ap;
+	char *buf;
+	int oid[4];
+
+	va_start(ap, fmt);
+	buf = setproctitle_internal(fmt, ap);
+	va_end(ap);
+
+	if (buf != NULL) {
+		/* Set the title into the kernel cached command line */
+		oid[0] = CTL_KERN;
+		oid[1] = KERN_PROC;
+		oid[2] = KERN_PROC_ARGS;
+		oid[3] = getpid();
+		sysctl(oid, 4, 0, 0, buf, strlen(buf) + 1);
+		fast_update = 0;
+	}
 }
-- 
2.45.0