kernel: Allocate user_mutex_contexts when adding the second thread to a team.

This allows us to gracefully fail if memory allocation fails,
rather than panic()ing. If a single-threaded application tries
to wait on a non-shared user_mutex in single-threaded mode, it
will now be dropped into the debugger.

headers/private/kernel/user_mutex.h

@@ -7,6 +7,7 @@
 
 
 #include <SupportDefs.h>
+#include <thread_types.h>
 
 
 #ifdef __cplusplus
@@ -17,6 +18,7 @@ struct user_mutex_context;
 
 void		user_mutex_init();
 void		delete_user_mutex_context(struct user_mutex_context* context);
+status_t	allocate_team_user_mutex_context(Team* team);
 
 status_t	_user_mutex_lock(int32* mutex, const char* name, uint32 flags,
 				bigtime_t timeout);

src/system/kernel/locks/user_mutex.cpp

@@ -219,31 +219,25 @@ user_mutex_init()
 }
 
 
-struct user_mutex_context*
-get_team_user_mutex_context()
+status_t
+allocate_team_user_mutex_context(Team* team)
 {
-	struct user_mutex_context* context =
-		thread_get_current_thread()->team->user_mutex_context;
-	if (context != NULL)
-		return context;
+	team->AssertLocked();
+	ASSERT(team->user_mutex_context == NULL);
 
-	Team* team = thread_get_current_thread()->team;
-	TeamLocker teamLocker(team);
-	if (team->user_mutex_context != NULL)
-		return team->user_mutex_context;
-
-	context = new(std::nothrow) user_mutex_context;
+	struct user_mutex_context* context = new(std::nothrow) user_mutex_context;
 	if (context == NULL)
-		return NULL;
+		return B_NO_MEMORY;
 
 	context->lock = RW_LOCK_INITIALIZER("user mutex table");
-	if (context->table.Init() != B_OK) {
+	status_t status = context->table.Init();
+	if (status != B_OK) {
 		delete context;
-		return NULL;
+		return status;
 	}
 
 	team->user_mutex_context = context;
-	return context;
+	return B_OK;
 }
 
 
@@ -469,10 +463,10 @@ struct UserMutexContextFetcher {
 		fAddress(0)
 	{
 		if (!fShared) {
-			fContext = get_team_user_mutex_context();
+			fContext = thread_get_current_thread()->team->user_mutex_context;
 			if (fContext == NULL) {
-				panic("UserMutexContext allocation failed!");
-				fInitStatus = B_NO_MEMORY;
+				_user_debugger("single-threaded team attempted mutex operation");
+				fInitStatus = EDEADLK;
 				return;
 			}
 

src/system/kernel/thread.cpp

@@ -46,6 +46,7 @@
 #include <tls.h>
 #include <user_runtime.h>
 #include <user_thread.h>
+#include <user_mutex.h>
 #include <vfs.h>
 #include <vm/vm.h>
 #include <vm/VMAddressSpace.h>
@@ -1084,6 +1085,13 @@ thread_create_thread(const ThreadCreationAttributes& attributes, bool kernel)
 
 	bool debugNewThread = false;
 	if (!kernel) {
+		// ensure there's a user_mutex_context, if this isn't the main thread
+		if (team->main_thread != NULL && team->user_mutex_context == NULL) {
+			status_t status = allocate_team_user_mutex_context(team);
+			if (status != B_OK)
+				return status;
+		}
+
 		// allocate the user_thread structure, if not already allocated
 		if (thread->user_thread == NULL) {
 			thread->user_thread = team_allocate_user_thread(team);