diff --git a/llvm/utils/lit/lit/main.py b/llvm/utils/lit/lit/main.py
@@ -205,6 +205,10 @@ def main(builtinParameters = {}):
     group.add_option("", "--xunit-xml-output", dest="xunit_output_file",
                       help=("Write XUnit-compatible XML test reports to the"
                             " specified file"), default=None)
+    group.add_option("", "--timeout", dest="maxIndividualTestTime",
+                     help="Maximum time to spend running a single test (in seconds)."
+                     "0 means no time limit. [Default: 0]",
+                    type=int, default=None)
     parser.add_option_group(group)
 
     group = OptionGroup(parser, "Test Selection")
@@ -275,6 +279,14 @@ def main(builtinParameters = {}):
             name,val = entry.split('=', 1)
         userParams[name] = val
 
+    # Decide what the requested maximum indvidual test time should be
+    if opts.maxIndividualTestTime != None:
+        maxIndividualTestTime = opts.maxIndividualTestTime
+    else:
+        # Default is zero
+        maxIndividualTestTime = 0
+
+
     # Create the global config object.
     litConfig = lit.LitConfig.LitConfig(
         progname = os.path.basename(sys.argv[0]),
@@ -287,12 +299,26 @@ def main(builtinParameters = {}):
         debug = opts.debug,
         isWindows = isWindows,
         params = userParams,
-        config_prefix = opts.configPrefix)
+        config_prefix = opts.configPrefix,
+        maxIndividualTestTime = maxIndividualTestTime)
 
     # Perform test discovery.
     run = lit.run.Run(litConfig,
                       lit.discovery.find_tests_for_inputs(litConfig, inputs))
 
+    # After test discovery the configuration might have changed
+    # the maxIndividualTestTime. If we explicitly set this on the
+    # command line then override what was set in the test configuration
+    if opts.maxIndividualTestTime != None:
+        if opts.maxIndividualTestTime != litConfig.maxIndividualTestTime:
+            litConfig.note(('The test suite configuration requested an individual'
+                ' test timeout of {0} seconds but a timeout of {1} seconds was'
+                ' requested on the command line. Forcing timeout to be {1}'
+                ' seconds')
+                .format(litConfig.maxIndividualTestTime,
+                        opts.maxIndividualTestTime))
+            litConfig.maxIndividualTestTime = opts.maxIndividualTestTime
+
     if opts.showSuites or opts.showTests:
         # Aggregate the tests by suite.
         suitesAndTests = {}
@@ -377,7 +403,6 @@ def main(builtinParameters = {}):
         extra = ' of %d' % numTotalTests
     header = '-- Testing: %d%s tests, %d threads --'%(len(run.tests), extra,
                                                       opts.numThreads)
-
     progressBar = None
     if not opts.quiet:
         if opts.succinct and opts.useProgressBar:
@@ -422,7 +447,8 @@ def main(builtinParameters = {}):
                        ('Failing Tests', lit.Test.FAIL),
                        ('Unresolved Tests', lit.Test.UNRESOLVED),
                        ('Unsupported Tests', lit.Test.UNSUPPORTED),
-                       ('Expected Failing Tests', lit.Test.XFAIL)):
+                       ('Expected Failing Tests', lit.Test.XFAIL),
+                       ('Timed Out Tests', lit.Test.TIMEOUT)):
         if (lit.Test.XFAIL == code and not opts.show_xfail) or \
            (lit.Test.UNSUPPORTED == code and not opts.show_unsupported):
             continue
@@ -447,7 +473,8 @@ def main(builtinParameters = {}):
                       ('Unsupported Tests  ', lit.Test.UNSUPPORTED),
                       ('Unresolved Tests   ', lit.Test.UNRESOLVED),
                       ('Unexpected Passes  ', lit.Test.XPASS),
-                      ('Unexpected Failures', lit.Test.FAIL)):
+                      ('Unexpected Failures', lit.Test.FAIL),
+                      ('Individual Timeouts', lit.Test.TIMEOUT)):
         if opts.quiet and not code.isFailure:
             continue
         N = len(byCode.get(code,[]))

diff --git a/llvm/utils/lit/lit/util.py b/llvm/utils/lit/lit/util.py
@@ -6,6 +6,7 @@
 import signal
 import subprocess
 import sys
+import threading
 
 def to_bytes(str):
     # Encode to UTF-8 to get binary data.
@@ -157,26 +158,83 @@ def printHistogram(items, title = 'Items'):
             pDigits, pfDigits, i*barH, pDigits, pfDigits, (i+1)*barH,
             '*'*w, ' '*(barW-w), cDigits, len(row), cDigits, len(items)))
 
+class ExecuteCommandTimeoutException(Exception):
+    def __init__(self, msg, out, err, exitCode):
+        assert isinstance(msg, str)
+        assert isinstance(out, str)
+        assert isinstance(err, str)
+        assert isinstance(exitCode, int)
+        self.msg = msg
+        self.out = out
+        self.err = err
+        self.exitCode = exitCode
+
 # Close extra file handles on UNIX (on Windows this cannot be done while
 # also redirecting input).
 kUseCloseFDs = not (platform.system() == 'Windows')
-def executeCommand(command, cwd=None, env=None, input=None):
+def executeCommand(command, cwd=None, env=None, input=None, timeout=0):
+    """
+        Execute command ``command`` (list of arguments or string)
+        with
+        * working directory ``cwd`` (str), use None to use the current
+          working directory
+        * environment ``env`` (dict), use None for none
+        * Input to the command ``input`` (str), use string to pass
+          no input.
+        * Max execution time ``timeout`` (int) seconds. Use 0 for no timeout.
+
+        Returns a tuple (out, err, exitCode) where
+        * ``out`` (str) is the standard output of running the command
+        * ``err`` (str) is the standard error of running the command
+        * ``exitCode`` (int) is the exitCode of running the command
+
+        If the timeout is hit an ``ExecuteCommandTimeoutException``
+        is raised.
+    """
     p = subprocess.Popen(command, cwd=cwd,
                          stdin=subprocess.PIPE,
                          stdout=subprocess.PIPE,
                          stderr=subprocess.PIPE,
                          env=env, close_fds=kUseCloseFDs)
-    out,err = p.communicate(input=input)
-    exitCode = p.wait()
+    timerObject = None
+    # FIXME: Because of the way nested function scopes work in Python 2.x we
+    # need to use a reference to a mutable object rather than a plain
+    # bool. In Python 3 we could use the "nonlocal" keyword but we need
+    # to support Python 2 as well.
+    hitTimeOut = [False]
+    try:
+        if timeout > 0:
+            def killProcess():
+                # We may be invoking a shell so we need to kill the
+                # process and all its children.
+                hitTimeOut[0] = True
+                killProcessAndChildren(p.pid)
 
-    # Detect Ctrl-C in subprocess.
-    if exitCode == -signal.SIGINT:
-        raise KeyboardInterrupt
+            timerObject = threading.Timer(timeout, killProcess)
+            timerObject.start()
+
+        out,err = p.communicate(input=input)
+        exitCode = p.wait()
+    finally:
+        if timerObject != None:
+            timerObject.cancel()
 
     # Ensure the resulting output is always of string type.
     out = convert_string(out)
     err = convert_string(err)
 
+    if hitTimeOut[0]:
+        raise ExecuteCommandTimeoutException(
+            msg='Reached timeout of {} seconds'.format(timeout),
+            out=out,
+            err=err,
+            exitCode=exitCode
+            )
+
+    # Detect Ctrl-C in subprocess.
+    if exitCode == -signal.SIGINT:
+        raise KeyboardInterrupt
+
     return out, err, exitCode
 
 def usePlatformSdkOnDarwin(config, lit_config):
@@ -195,3 +253,25 @@ def usePlatformSdkOnDarwin(config, lit_config):
             sdk_path = out
             lit_config.note('using SDKROOT: %r' % sdk_path)
             config.environment['SDKROOT'] = sdk_path
+
+def killProcessAndChildren(pid):
+    """
+    This function kills a process with ``pid`` and all its
+    running children (recursively). It is currently implemented
+    using the psutil module which provides a simple platform
+    neutral implementation.
+
+    TODO: Reimplement this without using psutil so we can
+          remove our dependency on it.
+    """
+    import psutil
+    try:
+        psutilProc = psutil.Process(pid)
+        for child in psutilProc.children(recursive=True):
+            try:
+                child.kill()
+            except psutil.NoSuchProcess:
+                pass
+        psutilProc.kill()
+    except psutil.NoSuchProcess:
+        pass
diff --git a/llvm/utils/lit/tests/Inputs/googletest-timeout/DummySubDir/OneTest b/llvm/utils/lit/tests/Inputs/googletest-timeout/DummySubDir/OneTest
@@ -0,0 +1,35 @@
+#!/usr/bin/env python
+
+import sys
+import time
+
+if len(sys.argv) != 2:
+    raise ValueError("unexpected number of args")
+
+if sys.argv[1] == "--gtest_list_tests":
+    print("""\
+FirstTest.
+  subTestA
+  subTestB
+  subTestC
+""")
+    sys.exit(0)
+elif not sys.argv[1].startswith("--gtest_filter="):
+    raise ValueError("unexpected argument: %r" % (sys.argv[1]))
+
+test_name = sys.argv[1].split('=',1)[1]
+if test_name == 'FirstTest.subTestA':
+    print('I am subTest A, I PASS')
+    print('[  PASSED  ] 1 test.')
+    sys.exit(0)
+elif test_name == 'FirstTest.subTestB':
+    print('I am subTest B, I am slow')
+    time.sleep(6)
+    print('[  PASSED  ] 1 test.')
+    sys.exit(0)
+elif test_name == 'FirstTest.subTestC':
+    print('I am subTest C, I will hang')
+    while True:
+        pass
+else:
+    raise SystemExit("error: invalid test name: %r" % (test_name,))
diff --git a/llvm/utils/lit/tests/Inputs/googletest-timeout/lit.cfg b/llvm/utils/lit/tests/Inputs/googletest-timeout/lit.cfg
@@ -0,0 +1,9 @@
+import lit.formats
+config.name = 'googletest-timeout'
+config.test_format = lit.formats.GoogleTest('DummySubDir', 'Test')
+
+configSetTimeout = lit_config.params.get('set_timeout', '0')
+
+if configSetTimeout == '1':
+    # Try setting the max individual test time in the configuration
+    lit_config.maxIndividualTestTime = 1
diff --git a/llvm/utils/lit/tests/Inputs/shtest-timeout/infinite_loop.py b/llvm/utils/lit/tests/Inputs/shtest-timeout/infinite_loop.py
@@ -0,0 +1,10 @@
+# RUN: %{python} %s
+from __future__ import print_function
+
+import time
+import sys
+
+print("Running infinite loop")
+sys.stdout.flush() # Make sure the print gets flushed so it appears in lit output.
+while True:
+    pass
diff --git a/llvm/utils/lit/tests/Inputs/shtest-timeout/lit.cfg b/llvm/utils/lit/tests/Inputs/shtest-timeout/lit.cfg
@@ -0,0 +1,32 @@
+# -*- Python -*-
+import os
+import sys
+
+import lit.formats
+
+config.name = 'per_test_timeout'
+
+shellType = lit_config.params.get('external', '1')
+
+if shellType == '0':
+    lit_config.note('Using internal shell')
+    externalShell = False
+else:
+    lit_config.note('Using external shell')
+    externalShell = True
+
+configSetTimeout = lit_config.params.get('set_timeout', '0')
+
+if configSetTimeout == '1':
+    # Try setting the max individual test time in the configuration
+    lit_config.maxIndividualTestTime = 1
+
+config.test_format = lit.formats.ShTest(execute_external=externalShell)
+config.suffixes = ['.py']
+
+config.test_source_root = os.path.dirname(__file__)
+config.test_exec_root = config.test_source_root
+config.target_triple = '(unused)'
+src_root = os.path.join(config.test_source_root, '..')
+config.environment['PYTHONPATH'] = src_root
+config.substitutions.append(('%{python}', sys.executable))
diff --git a/llvm/utils/lit/tests/Inputs/shtest-timeout/quick_then_slow.py b/llvm/utils/lit/tests/Inputs/shtest-timeout/quick_then_slow.py
@@ -0,0 +1,24 @@
+# RUN: %{python} %s quick
+# RUN: %{python} %s slow
+from __future__ import print_function
+
+import time
+import sys
+
+if len(sys.argv) != 2:
+    print("Wrong number of args")
+    sys.exit(1)
+
+mode =  sys.argv[1]
+
+if mode == 'slow':
+    print("Running in slow mode")
+    sys.stdout.flush() # Make sure the print gets flushed so it appears in lit output.
+    time.sleep(6)
+    sys.exit(0)
+elif mode == 'quick':
+    print("Running in quick mode")
+    sys.exit(0)
+else:
+    print("Unrecognised mode {}".format(mode))
+    sys.exit(1)
diff --git a/llvm/utils/lit/tests/Inputs/shtest-timeout/short.py b/llvm/utils/lit/tests/Inputs/shtest-timeout/short.py
@@ -0,0 +1,6 @@
+# RUN: %{python} %s
+from __future__ import print_function
+
+import sys
+
+print("short program")
diff --git a/llvm/utils/lit/tests/Inputs/shtest-timeout/slow.py b/llvm/utils/lit/tests/Inputs/shtest-timeout/slow.py
@@ -0,0 +1,9 @@
+# RUN: %{python} %s
+from __future__ import print_function
+
+import time
+import sys
+
+print("Running slow program")
+sys.stdout.flush() # Make sure the print gets flushed so it appears in lit output.
+time.sleep(6)
diff --git a/llvm/utils/lit/tests/googletest-timeout.py b/llvm/utils/lit/tests/googletest-timeout.py
@@ -0,0 +1,29 @@
+# REQUIRES: python-psutil
+
+# Check that the per test timeout is enforced when running GTest tests.
+#
+# RUN: not %{lit} -j 1 -v %{inputs}/googletest-timeout --timeout=1 > %t.cmd.out
+# RUN: FileCheck < %t.cmd.out %s
+
+# Check that the per test timeout is enforced when running GTest tests via
+# the configuration file
+#
+# RUN: not %{lit} -j 1 -v %{inputs}/googletest-timeout \
+# RUN: --param set_timeout=1 > %t.cfgset.out 2> %t.cfgset.err
+# RUN: FileCheck < %t.cfgset.out %s
+
+# CHECK: -- Testing:
+# CHECK: PASS: googletest-timeout :: DummySubDir/OneTest/FirstTest.subTestA
+# CHECK: TIMEOUT: googletest-timeout :: DummySubDir/OneTest/FirstTest.subTestB
+# CHECK: TIMEOUT: googletest-timeout :: DummySubDir/OneTest/FirstTest.subTestC
+# CHECK: Expected Passes    : 1
+# CHECK: Individual Timeouts: 2
+
+# Test per test timeout via a config file and on the command line.
+# The value set on the command line should override the config file.
+# RUN: not %{lit} -j 1 -v %{inputs}/googletest-timeout \
+# RUN: --param set_timeout=1 --timeout=2 > %t.cmdover.out 2> %t.cmdover.err
+# RUN: FileCheck < %t.cmdover.out %s
+# RUN: FileCheck --check-prefix=CHECK-CMDLINE-OVERRIDE-ERR < %t.cmdover.err %s
+
+# CHECK-CMDLINE-OVERRIDE-ERR: Forcing timeout to be 2 seconds
diff --git a/llvm/utils/lit/tests/lit.cfg b/llvm/utils/lit/tests/lit.cfg
@@ -43,3 +43,12 @@ if lit_config.params.get('check-coverage', None):
 # Add a feature to detect the Python version.
 config.available_features.add("python%d.%d" % (sys.version_info[0],
                                                   sys.version_info[1]))
+
+# Add a feature to detect if psutil is available
+try:
+    import psutil
+    lit_config.note('Found python psutil module')
+    config.available_features.add("python-psutil")
+except ImportError:
+    lit_config.warning('Could not import psutil. Some tests will be skipped and'
+                       ' the --timeout command line argument will not work.')
diff --git a/llvm/utils/lit/tests/shtest-timeout.py b/llvm/utils/lit/tests/shtest-timeout.py
@@ -0,0 +1,116 @@
+# REQUIRES: python-psutil
+
+# Test per test timeout using external shell
+# RUN: not %{lit} \
+# RUN: %{inputs}/shtest-timeout/infinite_loop.py \
+# RUN: %{inputs}/shtest-timeout/quick_then_slow.py \
+# RUN: %{inputs}/shtest-timeout/short.py \
+# RUN: %{inputs}/shtest-timeout/slow.py \
+# RUN: -j 1 -v --debug --timeout 1 --param external=1 > %t.extsh.out 2> %t.extsh.err
+# RUN: FileCheck --check-prefix=CHECK-OUT-COMMON < %t.extsh.out %s
+# RUN: FileCheck --check-prefix=CHECK-EXTSH-ERR < %t.extsh.err %s
+#
+# CHECK-EXTSH-ERR: Using external shell
+
+# Test per test timeout using internal shell
+# RUN: not %{lit} \
+# RUN: %{inputs}/shtest-timeout/infinite_loop.py \
+# RUN: %{inputs}/shtest-timeout/quick_then_slow.py \
+# RUN: %{inputs}/shtest-timeout/short.py \
+# RUN: %{inputs}/shtest-timeout/slow.py \
+# RUN: -j 1 -v --debug --timeout 1 --param external=0 > %t.intsh.out 2> %t.intsh.err
+# RUN: FileCheck  --check-prefix=CHECK-OUT-COMMON < %t.intsh.out %s
+# RUN: FileCheck --check-prefix=CHECK-INTSH-OUT < %t.intsh.out %s
+# RUN: FileCheck --check-prefix=CHECK-INTSH-ERR < %t.intsh.err %s
+#
+# CHECK-INTSH-OUT: TIMEOUT: per_test_timeout :: infinite_loop.py
+# CHECK-INTSH-OUT: Command 0 Reached Timeout: True
+# CHECK-INTSH-OUT: Command 0 Output:
+# CHECK-INTSH-OUT-NEXT: Running infinite loop
+
+
+# CHECK-INTSH-OUT: TIMEOUT: per_test_timeout :: quick_then_slow.py
+# CHECK-INTSH-OUT: Timeout: Reached timeout of 1 seconds
+# CHECK-INTSH-OUT: Command Output
+# CHECK-INTSH-OUT: Command 0 Reached Timeout: False
+# CHECK-INTSH-OUT: Command 0 Output:
+# CHECK-INTSH-OUT-NEXT: Running in quick mode
+# CHECK-INTSH-OUT: Command 1 Reached Timeout: True
+# CHECK-INTSH-OUT: Command 1 Output:
+# CHECK-INTSH-OUT-NEXT: Running in slow mode
+
+# CHECK-INTSH-OUT: TIMEOUT: per_test_timeout :: slow.py
+# CHECK-INTSH-OUT: Command 0 Reached Timeout: True
+# CHECK-INTSH-OUT: Command 0 Output:
+# CHECK-INTSH-OUT-NEXT: Running slow program
+
+# CHECK-INTSH-ERR: Using internal shell
+
+# Test per test timeout set via a config file rather than on the command line
+# RUN: not %{lit} \
+# RUN: %{inputs}/shtest-timeout/infinite_loop.py \
+# RUN: %{inputs}/shtest-timeout/quick_then_slow.py \
+# RUN: %{inputs}/shtest-timeout/short.py \
+# RUN: %{inputs}/shtest-timeout/slow.py \
+# RUN: -j 1 -v --debug --param external=0 \
+# RUN: --param set_timeout=1 > %t.cfgset.out 2> %t.cfgset.err
+# RUN: FileCheck --check-prefix=CHECK-OUT-COMMON  < %t.cfgset.out %s
+# RUN: FileCheck --check-prefix=CHECK-CFGSET-ERR < %t.cfgset.err %s
+#
+# CHECK-CFGSET-ERR: Using internal shell
+
+# CHECK-OUT-COMMON: TIMEOUT: per_test_timeout :: infinite_loop.py
+# CHECK-OUT-COMMON: Timeout: Reached timeout of 1 seconds
+# CHECK-OUT-COMMON: Command {{([0-9]+ )?}}Output
+# CHECK-OUT-COMMON: Running infinite loop
+
+# CHECK-OUT-COMMON: TIMEOUT: per_test_timeout :: quick_then_slow.py
+# CHECK-OUT-COMMON: Timeout: Reached timeout of 1 seconds
+# CHECK-OUT-COMMON: Command {{([0-9]+ )?}}Output
+# CHECK-OUT-COMMON: Running in quick mode
+# CHECK-OUT-COMMON: Running in slow mode
+
+# CHECK-OUT-COMMON: PASS: per_test_timeout :: short.py
+
+# CHECK-OUT-COMMON: TIMEOUT: per_test_timeout :: slow.py
+# CHECK-OUT-COMMON: Timeout: Reached timeout of 1 seconds
+# CHECK-OUT-COMMON: Command {{([0-9]+ )?}}Output
+# CHECK-OUT-COMMON: Running slow program
+
+# CHECK-OUT-COMMON: Expected Passes{{ *}}: 1
+# CHECK-OUT-COMMON: Individual Timeouts{{ *}}: 3
+
+# Test per test timeout via a config file and on the command line.
+# The value set on the command line should override the config file.
+# RUN: not %{lit} \
+# RUN: %{inputs}/shtest-timeout/infinite_loop.py \
+# RUN: %{inputs}/shtest-timeout/quick_then_slow.py \
+# RUN: %{inputs}/shtest-timeout/short.py \
+# RUN: %{inputs}/shtest-timeout/slow.py \
+# RUN: -j 1 -v --debug --param external=0 \
+# RUN: --param set_timeout=1 --timeout=2 > %t.cmdover.out 2> %t.cmdover.err
+# RUN: FileCheck --check-prefix=CHECK-CMDLINE-OVERRIDE-OUT  < %t.cmdover.out %s
+# RUN: FileCheck --check-prefix=CHECK-CMDLINE-OVERRIDE-ERR < %t.cmdover.err %s
+
+# CHECK-CMDLINE-OVERRIDE-ERR: Forcing timeout to be 2 seconds
+
+# CHECK-CMDLINE-OVERRIDE-OUT: TIMEOUT: per_test_timeout :: infinite_loop.py
+# CHECK-CMDLINE-OVERRIDE-OUT: Timeout: Reached timeout of 2 seconds
+# CHECK-CMDLINE-OVERRIDE-OUT: Command {{([0-9]+ )?}}Output
+# CHECK-CMDLINE-OVERRIDE-OUT: Running infinite loop
+
+# CHECK-CMDLINE-OVERRIDE-OUT: TIMEOUT: per_test_timeout :: quick_then_slow.py
+# CHECK-CMDLINE-OVERRIDE-OUT: Timeout: Reached timeout of 2 seconds
+# CHECK-CMDLINE-OVERRIDE-OUT: Command {{([0-9]+ )?}}Output
+# CHECK-CMDLINE-OVERRIDE-OUT: Running in quick mode
+# CHECK-CMDLINE-OVERRIDE-OUT: Running in slow mode
+
+# CHECK-CMDLINE-OVERRIDE-OUT: PASS: per_test_timeout :: short.py
+
+# CHECK-CMDLINE-OVERRIDE-OUT: TIMEOUT: per_test_timeout :: slow.py
+# CHECK-CMDLINE-OVERRIDE-OUT: Timeout: Reached timeout of 2 seconds
+# CHECK-CMDLINE-OVERRIDE-OUT: Command {{([0-9]+ )?}}Output
+# CHECK-CMDLINE-OVERRIDE-OUT: Running slow program
+
+# CHECK-CMDLINE-OVERRIDE-OUT: Expected Passes{{ *}}: 1
+# CHECK-CMDLINE-OVERRIDE-OUT: Individual Timeouts{{ *}}: 3