From 745118acb9205e502c145963f7c7afb7f4da10b3 Mon Sep 17 00:00:00 2001
From: Oron Peled <oron.peled@xorcom.com>
Date: Sun, 29 Sep 2013 13:20:38 +0200
Subject: [PATCH] xpp: Serialize dahdi registration

xpp: Serialize dahdi registration: Cause races under highly-parallel
workloads (with dahdi_autoreg=0).

Signed-off-by: Tzafrir Cohen <tzafrir.cohen@xorcom.com>
---
 drivers/dahdi/xpp/xbus-core.c  | 22 ++++++++++++++++++++--
 drivers/dahdi/xpp/xbus-sysfs.c |  9 +++++++++
 2 files changed, 29 insertions(+), 2 deletions(-)

diff --git a/drivers/dahdi/xpp/xbus-core.c b/drivers/dahdi/xpp/xbus-core.c
index c2fb00f..7a7c368 100644
--- a/drivers/dahdi/xpp/xbus-core.c
+++ b/drivers/dahdi/xpp/xbus-core.c
@@ -24,6 +24,7 @@
 #include <linux/module.h>
 #include <linux/errno.h>
 #include <linux/sched.h>
+#include <linux/mutex.h>
 #include <linux/proc_fs.h>
 #include <linux/seq_file.h>
 #ifdef	PROTOCOL_DEBUG
@@ -937,6 +938,8 @@ static void xbus_free_ddev(xbus_t *xbus)
 	xbus->ddev = NULL;
 }
 
+static DEFINE_MUTEX(dahdi_registration_mutex);
+
 int xbus_register_dahdi_device(xbus_t *xbus)
 {
 	int i;
@@ -944,6 +947,11 @@ int xbus_register_dahdi_device(xbus_t *xbus)
 	int ret;
 
 	XBUS_DBG(DEVICES, xbus, "Entering %s\n", __func__);
+	ret = mutex_lock_interruptible(&dahdi_registration_mutex);
+	if (ret < 0) {
+		XBUS_ERR(xbus, "dahdi_registration_mutex already taken\n");
+		goto err;
+	}
 	if (xbus_is_registered(xbus)) {
 		XBUS_ERR(xbus, "Already registered to DAHDI\n");
 		WARN_ON(1);
@@ -1008,17 +1016,26 @@ int xbus_register_dahdi_device(xbus_t *xbus)
 			xpd_dahdi_postregister(xpd);
 		}
 	}
-	return 0;
+	ret = 0;
+out:
+	mutex_unlock(&dahdi_registration_mutex);
+	return ret;
 err:
 	xbus_free_ddev(xbus);
-	return ret;
+	goto out;
 }
 
 void xbus_unregister_dahdi_device(xbus_t *xbus)
 {
 	int i;
+	int ret;
 
 	XBUS_NOTICE(xbus, "%s\n", __func__);
+	ret = mutex_lock_interruptible(&dahdi_registration_mutex);
+	if (ret < 0) {
+		XBUS_ERR(xbus, "dahdi_registration_mutex already taken\n");
+		return;
+	}
 	for (i = 0; i < MAX_XPDS; i++) {
 		xpd_t *xpd = xpd_of(xbus, i);
 		xpd_dahdi_preunregister(xpd);
@@ -1033,6 +1050,7 @@ void xbus_unregister_dahdi_device(xbus_t *xbus)
 		xpd_t *xpd = xpd_of(xbus, i);
 		xpd_dahdi_postunregister(xpd);
 	}
+	mutex_unlock(&dahdi_registration_mutex);
 }
 
 /*
diff --git a/drivers/dahdi/xpp/xbus-sysfs.c b/drivers/dahdi/xpp/xbus-sysfs.c
index ad58e15..956e765 100644
--- a/drivers/dahdi/xpp/xbus-sysfs.c
+++ b/drivers/dahdi/xpp/xbus-sysfs.c
@@ -23,6 +23,7 @@
 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/errno.h>
+#include <linux/mutex.h>
 #include <linux/proc_fs.h>
 #ifdef	PROTOCOL_DEBUG
 #include <linux/ctype.h>
@@ -582,6 +583,8 @@ static DEVICE_ATTR_READER(span_show, dev, buf)
 	return len;
 }
 
+static DEFINE_MUTEX(span_store_mutex);
+
 /*
  * For backward compatibility with old dahdi-tools
  * Remove after dahdi_registration is upgraded
@@ -603,6 +606,11 @@ static DEVICE_ATTR_WRITER(span_store, dev, buf, count)
 		return -ENODEV;
 	XPD_DBG(DEVICES, xpd, "%s -- deprecated (should use pinned-spans)\n",
 		(dahdi_reg) ? "register" : "unregister");
+	ret = mutex_lock_interruptible(&span_store_mutex);
+	if (ret < 0) {
+		XBUS_ERR(xpd->xbus, "span_store_mutex already taken\n");
+		return ret;
+	}
 	if (xbus_is_registered(xpd->xbus)) {
 		if (dahdi_reg) {
 			XPD_DBG(DEVICES, xpd,
@@ -620,6 +628,7 @@ static DEVICE_ATTR_WRITER(span_store, dev, buf, count)
 			xbus_register_dahdi_device(xpd->xbus);
 		}
 	}
+	mutex_unlock(&span_store_mutex);
 	return count;
 }