From 065ef7eb5f0f5e124c6876b73dd47f95c5038395 Mon Sep 17 00:00:00 2001
From: Michael Lotz <mmlr@mlotz.ch>
Date: Thu, 5 Jun 2008 18:58:03 +0000
Subject: [PATCH] Replace the legacy driver mutex with a recursive lock. This
 fixes the deadlock when hot-plugging a USB mass storage device. The legacy
 driver (usb_disk in this case) was rescanned which locked the legacy driver
 mutex. The insertion of the new device node caused the disk device manager
 (notified through node monitoring) to try to scan the new node. As opening
 the node triggers LegacyDevice::InitDevice() that locks the legacy driver
 mutex again a deadlock occured.

git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@25807 a95241bf-73f2-0310-859d-f6bbb57e9c96
---
 .../kernel/device_manager/legacy_drivers.cpp  | 22 +++++++++----------
 1 file changed, 10 insertions(+), 12 deletions(-)

diff --git a/src/system/kernel/device_manager/legacy_drivers.cpp b/src/system/kernel/device_manager/legacy_drivers.cpp
index 86621b1603..da035de94e 100644
--- a/src/system/kernel/device_manager/legacy_drivers.cpp
+++ b/src/system/kernel/device_manager/legacy_drivers.cpp
@@ -185,7 +185,7 @@ static int32 sDriverEvents;
 static DoublyLinkedList<path_entry> sDriversToAdd;
 static DirectoryWatcher sDirectoryWatcher;
 static DirectoryNodeHash sDirectoryNodeHash;
-static mutex sLock;
+static recursive_lock sLock;
 static bool sWatching;
 
 
@@ -575,8 +575,7 @@ add_driver(const char *path, image_id image)
 
 	int32 priority = get_priority(path);
 
-//	RecursiveLocker locker(&sDeviceFileSystem->lock);
-	MutexLocker _(sLock);
+	RecursiveLocker _(sLock);
 
 	legacy_driver *driver = (legacy_driver *)hash_lookup(sDriverHash,
 		get_leaf(path));
@@ -678,8 +677,7 @@ handle_driver_events(void *_fs, int /*iteration*/)
 
 	// something happened, let's see what it was
 
-//	RecursiveLocker locker(fs->lock);
-	MutexLocker locker(sLock);
+	RecursiveLocker locker(sLock);
 
 	while (true) {
 		path_entry *path = sDriversToAdd.RemoveHead();
@@ -729,7 +727,7 @@ DriverWatcher::EventOccured(NotificationService& service,
 		|| (event->GetInt32("fields", 0) & B_STAT_MODIFICATION_TIME) == 0)
 		return;
 
-	MutexLocker locker(sLock);
+	RecursiveLocker locker(sLock);
 
 	legacy_driver* driver = find_driver(event->GetInt32("device", -1),
 		event->GetInt64("node", 0));
@@ -1172,7 +1170,7 @@ LegacyDevice::InitCheck() const
 status_t
 LegacyDevice::InitDevice()
 {
-	MutexLocker _(sLock);
+	RecursiveLocker _(sLock);
 
 	if (fInitialized++ > 0)
 		return B_OK;
@@ -1194,7 +1192,7 @@ LegacyDevice::InitDevice()
 void
 LegacyDevice::UninitDevice()
 {
-	MutexLocker _(sLock);
+	RecursiveLocker _(sLock);
 
 	if (fInitialized-- > 1)
 		return;
@@ -1301,7 +1299,7 @@ extern "C" void
 devfs_driver_added(const char *path)
 {
 	int32 priority = get_priority(path);
-	MutexLocker locker(sLock);
+	RecursiveLocker locker(sLock);
 
 	legacy_driver *driver = (legacy_driver *)hash_lookup(sDriverHash,
 		get_leaf(path));
@@ -1330,7 +1328,7 @@ extern "C" void
 devfs_driver_removed(const char* path)
 {
 	int32 priority = get_priority(path);
-	MutexLocker locker(sLock);
+	RecursiveLocker locker(sLock);
 
 	legacy_driver* driver = (legacy_driver*)hash_lookup(sDriverHash,
 		get_leaf(path));
@@ -1364,7 +1362,7 @@ legacy_driver_publish(const char *path, device_hooks *hooks)
 extern "C" status_t
 legacy_driver_rescan(const char* driverName)
 {
-	MutexLocker locker(sLock);
+	RecursiveLocker locker(sLock);
 
 	legacy_driver* driver = (legacy_driver*)hash_lookup(sDriverHash,
 		driverName);
@@ -1429,7 +1427,7 @@ legacy_driver_init(void)
 	if (sDriverHash == NULL)
 		return B_NO_MEMORY;
 
-	mutex_init(&sLock, "legacy driver");
+	recursive_lock_init(&sLock, "legacy driver");
 
 	new(&sDriverWatcher) DriverWatcher;
 	new(&sDriversToAdd) DoublyLinkedList<path_entry>;