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From: John Baldwin <jhb@FreeBSD.org>
Date: Thu, 11 Jun 2009 21:37:24 +0000 (UTC)
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Subject: svn commit: r194040 - stable/7/lib/libc/gen
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Author: jhb
Date: Thu Jun 11 21:37:23 2009
New Revision: 194040
URL: http://svn.freebsd.org/changeset/base/194040

Log:
  If the running kernel has support for shm_open() and shm_unlink() as
  system calls (i.e. 8.0+), then invoke the system calls instead of using
  open/fcntl/unlink.  This is a direct commit instead of an MFC since libc
  in 8.0 always uses the system calls directly.
  
  MFC after:	1 week

Modified:
  stable/7/lib/libc/gen/posixshm.c

Modified: stable/7/lib/libc/gen/posixshm.c
==============================================================================
--- stable/7/lib/libc/gen/posixshm.c	Thu Jun 11 21:32:26 2009	(r194039)
+++ stable/7/lib/libc/gen/posixshm.c	Thu Jun 11 21:37:23 2009	(r194040)
@@ -40,12 +40,34 @@ __FBSDID("$FreeBSD$");
 #include <unistd.h>
 #include "un-namespace.h"
 
+static int _shm_in_kernel = -1;
+
+/* Wrappers for POSIX SHM system calls in newer kernels. */
+static __inline int
+_shm_open(const char *path, int flags, mode_t mode)
+{
+
+    return (syscall(482, path, flags, mode));
+}
+
+static __inline int
+_shm_unlink(const char *path)
+{
+
+    return (syscall(483, path));
+}
+
 int
 shm_open(const char *path, int flags, mode_t mode)
 {
 	int fd;
 	struct stat stab;
 
+	if (_shm_in_kernel == -1)
+		_shm_in_kernel = feature_present("posix_shm");
+	if (_shm_in_kernel == 1)
+		return (_shm_open(path, flags, mode));
+
 	if ((flags & O_ACCMODE) == O_WRONLY)
 		return (EINVAL);
 
@@ -68,5 +90,11 @@ shm_open(const char *path, int flags, mo
 int
 shm_unlink(const char *path)
 {
+
+	if (_shm_in_kernel == -1)
+		_shm_in_kernel = feature_present("posix_shm");
+	if (_shm_in_kernel == 1)
+		return (_shm_unlink(path));
+
 	return (unlink(path));
 }