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From: Ed Schouten <ed@FreeBSD.org>
Date: Mon, 11 May 2009 18:52:46 +0000 (UTC)
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Subject: svn commit: r191999 - head/sys/dev/snp
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Author: ed
Date: Mon May 11 18:52:46 2009
New Revision: 191999
URL: http://svn.freebsd.org/changeset/base/191999

Log:
  Add macros around the sx operations in snp(4).
  
  As an experiment, I changed snp(4) to use a mutex instead of an sx lock.
  We can't enable this right now, because Syscons still picks up Giant.
  It's nice to already have the framework there.

Modified:
  head/sys/dev/snp/snp.c

Modified: head/sys/dev/snp/snp.c
==============================================================================
--- head/sys/dev/snp/snp.c	Mon May 11 18:45:04 2009	(r191998)
+++ head/sys/dev/snp/snp.c	Mon May 11 18:52:46 2009	(r191999)
@@ -43,11 +43,22 @@ __FBSDID("$FreeBSD$");
 #include <sys/uio.h>
 
 static struct cdev	*snp_dev;
+static MALLOC_DEFINE(M_SNP, "snp", "tty snoop device");
+
 /* XXX: should be mtx, but TTY can be locked by Giant. */
+#if 0
+static struct mtx	snp_register_lock;
+MTX_SYSINIT(snp_register_lock, &snp_register_lock,
+    "tty snoop registration", MTX_DEF);
+#define	SNP_LOCK()	mtx_lock(&snp_register_lock)
+#define	SNP_UNLOCK()	mtx_unlock(&snp_register_lock)
+#else
 static struct sx	snp_register_lock;
 SX_SYSINIT(snp_register_lock, &snp_register_lock,
     "tty snoop registration");
-static MALLOC_DEFINE(M_SNP, "snp", "tty snoop device");
+#define	SNP_LOCK()	sx_xlock(&snp_register_lock)
+#define	SNP_UNLOCK()	sx_xunlock(&snp_register_lock)
+#endif
 
 /*
  * There is no need to have a big input buffer. In most typical setups,
@@ -241,14 +252,14 @@ snp_ioctl(struct cdev *dev, u_long cmd, 
 	switch (cmd) {
 	case SNPSTTY:
 		/* Bind TTY to snoop instance. */
-		sx_xlock(&snp_register_lock);
+		SNP_LOCK();
 		if (ss->snp_tty != NULL) {
-			sx_xunlock(&snp_register_lock);
+			SNP_UNLOCK();
 			return (EBUSY);
 		}
 		error = ttyhook_register(&ss->snp_tty, td->td_proc, *(int *)data,
 		    &snp_hook, ss);
-		sx_xunlock(&snp_register_lock);
+		SNP_UNLOCK();
 		if (error != 0)
 			return (error);