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From: Ed Schouten <ed@FreeBSD.org>
To: Perforce Change Reviews <perforce@FreeBSD.org>
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Subject: PERFORCE change 148018 for review
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http://perforce.freebsd.org/chv.cgi?CH=148018

Change 148018 by ed@ed_flippo on 2008/08/21 17:42:30

	Reintroduce the 's' state in pstat(8) to indicate a TTY is being
	snooped.
	
	While there, change the mutex used to lock down hook
	registration to a sx(9). Because TTY's can be locked down by
	Giant, it is not possible to lock registration down with a
	non-sleepable lock.

Affected files ...

.. //depot/projects/mpsafetty/sys/dev/snp/snp.c#4 edit
.. //depot/projects/mpsafetty/sys/kern/tty.c#25 edit
.. //depot/projects/mpsafetty/usr.sbin/pstat/pstat.8#5 edit
.. //depot/projects/mpsafetty/usr.sbin/pstat/pstat.c#7 edit

Differences ...

==== //depot/projects/mpsafetty/sys/dev/snp/snp.c#4 (text+ko) ====

@@ -33,13 +33,15 @@
 #include <sys/malloc.h>
 #include <sys/module.h>
 #include <sys/snoop.h>
+#include <sys/sx.h>
 #include <sys/systm.h>
 #include <sys/tty.h>
 
 static struct cdev	*snp_dev;
-static struct mtx	snp_register_mtx;
-MTX_SYSINIT(snp_register_mtx, &snp_register_mtx,
-    "tty snoop registration", MTX_DEF);
+static struct sx	snp_register_lock;
+/* XXX: should be mtx, but TTY can be locked by Giant */
+SX_SYSINIT(snp_register_lock, &snp_register_lock,
+    "tty snoop registration");
 static MALLOC_DEFINE(M_SNP, "snp", "tty snoop device");
 
 static d_open_t		snp_open;
@@ -111,14 +113,14 @@
 	switch (cmd) {
 	case SNPSTTY:
 		/* Bind TTY to snoop instance */
-		mtx_lock(&snp_register_mtx);
+		sx_xlock(&snp_register_lock);
 		if (ss->snp_tty != NULL) {
-			mtx_unlock(&snp_register_mtx);
+			sx_xunlock(&snp_register_lock);
 			return (EBUSY);
 		}
 		error = ttyhook_register(&ss->snp_tty, td, *(int *)data,
 		    &snp_hook, ss);
-		mtx_unlock(&snp_register_mtx);
+		sx_xunlock(&snp_register_lock);
 		return (error);
 	case SNPGTTY:
 		/* Obtain device number of associated TTY */

==== //depot/projects/mpsafetty/sys/kern/tty.c#25 (text+ko) ====

@@ -1758,6 +1758,7 @@
 	{ TF_EXCLUDE,	'X' },
 	{ TF_BYPASS,	'l' },
 	{ TF_ZOMBIE,	'Z' },
+	{ TF_HOOK,	's' },
 
 	{ 0,	       '\0' },
 };

==== //depot/projects/mpsafetty/usr.sbin/pstat/pstat.8#5 (text+ko) ====

@@ -202,6 +202,8 @@
 block mode input routine in use
 .It Z
 connection lost
+.It s
+i/o being snooped
 .El
 .Pp
 The

==== //depot/projects/mpsafetty/usr.sbin/pstat/pstat.c#7 (text+ko) ====

@@ -312,6 +312,7 @@
 	{ TF_EXCLUDE,	'X' },
 	{ TF_BYPASS,	'l' },
 	{ TF_ZOMBIE,	'Z' },
+	{ TF_HOOK,	's' },
 
 	{ 0,	       '\0' },
 };