diff --git a/llvm/utils/lit/tests/Inputs/googletest-timeout/DummySubDir/OneTest.py b/llvm/utils/lit/tests/Inputs/googletest-timeout/DummySubDir/OneTest.py
--- a/llvm/utils/lit/tests/Inputs/googletest-timeout/DummySubDir/OneTest.py
+++ b/llvm/utils/lit/tests/Inputs/googletest-timeout/DummySubDir/OneTest.py
@@ -8,27 +8,21 @@
 
 if sys.argv[1] == "--gtest_list_tests":
     print("""\
-FirstTest.
-  subTestA
-  subTestB
-  subTestC
+T.
+  QuickSubTest
+  InfiniteLoopSubTest
 """)
     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')
+if test_name == 'T.QuickSubTest':
+    print('I am QuickSubTest, 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')
+elif test_name == 'T.InfiniteLoopSubTest':
+    print('I am InfiniteLoopSubTest, I will hang')
     while True:
         pass
 else:
diff --git a/llvm/utils/lit/tests/googletest-timeout.py b/llvm/utils/lit/tests/googletest-timeout.py
--- a/llvm/utils/lit/tests/googletest-timeout.py
+++ b/llvm/utils/lit/tests/googletest-timeout.py
@@ -1,29 +1,47 @@
 # REQUIRES: lit-max-individual-test-time
 
+###############################################################################
+# Check tests can hit timeout when set
+###############################################################################
+
 # 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
+# RUN: not %{lit} -j 1 -v %{inputs}/googletest-timeout \
+# RUN:   --filter=InfiniteLoopSubTest --timeout=1 > %t.cmd.out
+# RUN: FileCheck --check-prefix=CHECK-INF < %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
+# RUN:  --filter=InfiniteLoopSubTest  --param set_timeout=1 \
+# RUN:  > %t.cfgset.out
+# RUN: FileCheck --check-prefix=CHECK-INF < %t.cfgset.out %s
 
-# CHECK: -- Testing:
-# CHECK: PASS: googletest-timeout :: {{[Dd]ummy[Ss]ub[Dd]ir}}/OneTest.py/FirstTest.subTestA
-# CHECK: TIMEOUT: googletest-timeout :: {{[Dd]ummy[Ss]ub[Dd]ir}}/OneTest.py/FirstTest.subTestB
-# CHECK: TIMEOUT: googletest-timeout :: {{[Dd]ummy[Ss]ub[Dd]ir}}/OneTest.py/FirstTest.subTestC
-# CHECK: Passed   : 1
-# CHECK: Timed Out: 2
+# CHECK-INF: -- Testing:
+# CHECK-INF: TIMEOUT: googletest-timeout :: {{[Dd]ummy[Ss]ub[Dd]ir}}/OneTest.py/T.InfiniteLoopSubTest
+# CHECK-INF: Timed Out: 1
+
+###############################################################################
+# Check tests can complete with a timeout set
+#
+# `QuickSubTest` should execute quickly so we shouldn't wait anywhere near the
+# 3600 second timeout.
+###############################################################################
+
+# RUN: %{lit} -j 1 -v %{inputs}/googletest-timeout \
+# RUN:   --filter=QuickSubTest --timeout=3600 > %t.cmd.out
+# RUN: FileCheck --check-prefix=CHECK-QUICK < %t.cmd.out %s
+
+# CHECK-QUICK: PASS: googletest-timeout :: {{[Dd]ummy[Ss]ub[Dd]ir}}/OneTest.py/T.QuickSubTest
+# CHECK-QUICK: Passed : 1
 
 # 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: %{lit} -j 1 -v %{inputs}/googletest-timeout --filter=QuickSubTest \
+# RUN:   --param set_timeout=1 --timeout=3600 \
+# RUN:   > %t.cmdover.out 2> %t.cmdover.err
+# RUN: FileCheck --check-prefix=CHECK-QUICK < %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-ERR: Forcing timeout to be 3600 seconds
diff --git a/llvm/utils/lit/tests/shtest-timeout.py b/llvm/utils/lit/tests/shtest-timeout.py
--- a/llvm/utils/lit/tests/shtest-timeout.py
+++ b/llvm/utils/lit/tests/shtest-timeout.py
@@ -3,16 +3,14 @@
 # llvm.org/PR33944
 # UNSUPPORTED: system-windows
 
-# FIXME: This test is fragile because it relies on time which can
-# be affected by system performance. In particular we are currently
-# assuming that `short.py` can be successfully executed within 2
-# seconds of wallclock time.
+###############################################################################
+# Check tests can hit timeout when set
+###############################################################################
 
 # Test per test timeout using external shell
 # RUN: not %{lit} \
 # RUN: %{inputs}/shtest-timeout/infinite_loop.py \
-# RUN: %{inputs}/shtest-timeout/short.py \
-# RUN: -j 1 -v --debug --timeout 2 --param external=1 > %t.extsh.out 2> %t.extsh.err
+# 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
 #
@@ -21,8 +19,7 @@
 # Test per test timeout using internal shell
 # RUN: not %{lit} \
 # RUN: %{inputs}/shtest-timeout/infinite_loop.py \
-# RUN: %{inputs}/shtest-timeout/short.py \
-# RUN: -j 1 -v --debug --timeout 2 --param external=0 > %t.intsh.out 2> %t.intsh.err
+# 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
@@ -36,40 +33,50 @@
 # 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/short.py \
 # RUN: -j 1 -v --debug --param external=0 \
-# RUN: --param set_timeout=2 > %t.cfgset.out 2> %t.cfgset.err
+# 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 2 seconds
+# CHECK-OUT-COMMON: Timeout: Reached timeout of 1 seconds
 # CHECK-OUT-COMMON: Command {{([0-9]+ )?}}Output
+# CHECK-OUT-COMMON: Timed Out: 1
 
-# CHECK-OUT-COMMON: PASS: per_test_timeout :: short.py
 
-# CHECK-OUT-COMMON: Passed   : 1
-# CHECK-OUT-COMMON: Timed Out: 1
+###############################################################################
+# Check tests can complete in with a timeout set
+#
+# `short.py` should execute quickly so we shouldn't wait anywhere near the
+# 3600 second timeout.
+###############################################################################
 
-# 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 \
+# Test per test timeout using external shell
+# RUN: %{lit} \
 # RUN: %{inputs}/shtest-timeout/short.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
+# RUN: -j 1 -v --debug --timeout 3600 --param external=1 > %t.pass.extsh.out 2> %t.pass.extsh.err
+# RUN: FileCheck --check-prefix=CHECK-OUT-COMMON-SHORT < %t.pass.extsh.out %s
+# RUN: FileCheck --check-prefix=CHECK-EXTSH-ERR < %t.pass.extsh.err %s
 
-# CHECK-CMDLINE-OVERRIDE-ERR: Forcing timeout to be 2 seconds
+# Test per test timeout using internal shell
+# RUN: %{lit} \
+# RUN: %{inputs}/shtest-timeout/short.py \
+# RUN: -j 1 -v --debug --timeout 3600 --param external=0 > %t.pass.intsh.out 2> %t.pass.intsh.err
+# RUN: FileCheck  --check-prefix=CHECK-OUT-COMMON-SHORT < %t.pass.intsh.out %s
+# RUN: FileCheck --check-prefix=CHECK-INTSH-ERR < %t.pass.intsh.err %s
 
-# 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-OUT-COMMON-SHORT: PASS: per_test_timeout :: short.py
+# CHECK-OUT-COMMON-SHORT: Passed: 1
 
-# CHECK-CMDLINE-OVERRIDE-OUT: PASS: per_test_timeout :: short.py
+# 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: %{lit} \
+# RUN:   %{inputs}/shtest-timeout/short.py \
+# RUN:   -j 1 -v --debug --param external=0 \
+# RUN: --param set_timeout=1 --timeout=3600 > %t.pass.cmdover.out 2> %t.pass.cmdover.err
+# RUN: FileCheck --check-prefix=CHECK-OUT-COMMON-SHORT  < %t.pass.cmdover.out %s
+# RUN: FileCheck --check-prefix=CHECK-CMDLINE-OVERRIDE-ERR < %t.pass.cmdover.err %s
 
-# CHECK-CMDLINE-OVERRIDE-OUT: Passed   : 1
-# CHECK-CMDLINE-OVERRIDE-OUT: Timed Out: 1
+# CHECK-CMDLINE-OVERRIDE-ERR: Forcing timeout to be 3600 seconds