diff --git a/llvm/utils/lit/lit/LitConfig.py b/llvm/utils/lit/lit/LitConfig.py
--- a/llvm/utils/lit/lit/LitConfig.py
+++ b/llvm/utils/lit/lit/LitConfig.py
@@ -21,7 +21,7 @@
 
     def __init__(self, progname, path, quiet,
                  useValgrind, valgrindLeakCheck, valgrindArgs,
-                 noExecute, debug, isWindows, singleProcess,
+                 noExecute, debug, isWindows,
                  params, config_prefix = None,
                  maxIndividualTestTime = 0,
                  maxFailures = None,
@@ -37,7 +37,6 @@
         self.valgrindUserArgs = list(valgrindArgs)
         self.noExecute = noExecute
         self.debug = debug
-        self.singleProcess = singleProcess
         self.isWindows = bool(isWindows)
         self.params = dict(params)
         self.bashPath = None
diff --git a/llvm/utils/lit/lit/discovery.py b/llvm/utils/lit/lit/discovery.py
--- a/llvm/utils/lit/lit/discovery.py
+++ b/llvm/utils/lit/lit/discovery.py
@@ -262,7 +262,6 @@
                                     useValgrind = False,
                                     valgrindLeakCheck = False,
                                     valgrindArgs = [],
-                                    singleProcess=False,
                                     noExecute = False,
                                     debug = False,
                                     isWindows = (platform.system()=='Windows'),
diff --git a/llvm/utils/lit/lit/main.py b/llvm/utils/lit/lit/main.py
--- a/llvm/utils/lit/lit/main.py
+++ b/llvm/utils/lit/lit/main.py
@@ -336,11 +336,11 @@
     if not args:
         parser.error('No inputs specified')
 
-    if opts.numThreads is None:
-        opts.numThreads = lit.util.detectCPUs()
+    if opts.numThreads is not None and opts.numThreads <= 0:
+        parser.error("Option '--threads' or '-j' requires positive integer")
 
-    if opts.maxFailures == 0:
-        parser.error("Setting --max-failures to 0 does not have any effect.")
+    if opts.maxFailures is not None and opts.maxFailures <= 0:
+        parser.error("Option '--max-failures' requires positive integer")
 
     if opts.echoAllCommands:
         opts.showOutput = True
@@ -374,7 +374,6 @@
         valgrindLeakCheck = opts.valgrindLeakCheck,
         valgrindArgs = opts.valgrindArgs,
         noExecute = opts.noExecute,
-        singleProcess = opts.singleProcess,
         debug = opts.debug,
         isWindows = isWindows,
         params = userParams,
@@ -481,6 +480,12 @@
     if opts.maxTests is not None:
         run.tests = run.tests[:opts.maxTests]
 
+    # Determine number of threads to use.
+    if opts.singleProcess:
+        opts.numThreads = 1
+    elif opts.numThreads is None:
+        opts.numThreads = lit.util.detectCPUs()
+
     # Don't create more threads than tests.
     opts.numThreads = min(len(run.tests), opts.numThreads)
 
@@ -506,11 +511,9 @@
     except:
         pass
 
-    extra = ''
-    if len(run.tests) != numTotalTests:
-        extra = ' of %d' % numTotalTests
-    header = '-- Testing: %d%s tests, %d threads --'%(len(run.tests), extra,
-                                                      opts.numThreads)
+    extra = (' of %d' % numTotalTests) if (len(run.tests) != numTotalTests) else ''
+    threads = 'single process' if (opts.numThreads == 1) else ('%d threads' % opts.numThreads)
+    header = '-- Testing: %d%s tests, %s --' % (len(run.tests), extra, threads)
     progressBar = None
     if not opts.quiet:
         if opts.succinct and opts.useProgressBar:
diff --git a/llvm/utils/lit/lit/run.py b/llvm/utils/lit/lit/run.py
--- a/llvm/utils/lit/lit/run.py
+++ b/llvm/utils/lit/lit/run.py
@@ -113,7 +113,7 @@
         be given an UNRESOLVED result.
         """
         # Don't do anything if we aren't going to run any tests.
-        if not self.tests or jobs == 0:
+        if not self.tests:
             return
 
         # Save the display object on the runner so that we can update it from
@@ -122,10 +122,12 @@
 
         self.failure_count = 0
         self.hit_max_failures = False
-        if self.lit_config.singleProcess:
+        if jobs == 1:
             for test_index, test in enumerate(self.tests):
                 lit.worker._execute_test(test, self.lit_config)
                 self.consume_test_result((test_index, test))
+                if self.hit_max_failures:
+                    break
         else:
             self.execute_tests_in_pool(jobs, max_time)
 
diff --git a/llvm/utils/lit/lit/worker.py b/llvm/utils/lit/lit/worker.py
--- a/llvm/utils/lit/lit/worker.py
+++ b/llvm/utils/lit/lit/worker.py
@@ -1,5 +1,5 @@
 # The code in this file runs in a separate worker process.
-# Exception: if lit_config.singleProcess then _execute_test is called directly.
+# Exception: in single process mode _execute_test is called directly.
 import time
 import traceback
 
diff --git a/llvm/utils/lit/tests/max-failures.py b/llvm/utils/lit/tests/max-failures.py
--- a/llvm/utils/lit/tests/max-failures.py
+++ b/llvm/utils/lit/tests/max-failures.py
@@ -11,4 +11,4 @@
 # CHECK: Failing Tests (27)
 # CHECK: Failing Tests (1)
 # CHECK: Failing Tests (2)
-# CHECK: error: Setting --max-failures to 0 does not have any effect.
+# CHECK: error: Option '--max-failures' requires positive integer
diff --git a/llvm/utils/lit/tests/unit/TestRunner.py b/llvm/utils/lit/tests/unit/TestRunner.py
--- a/llvm/utils/lit/tests/unit/TestRunner.py
+++ b/llvm/utils/lit/tests/unit/TestRunner.py
@@ -29,7 +29,6 @@
                                              quiet=False,
                                              useValgrind=False,
                                              valgrindLeakCheck=False,
-                                             singleProcess=False,
                                              valgrindArgs=[],
                                              noExecute=False,
                                              debug=False,