SERVER-45677 libunwind on by default where possible

    - SCons configure to probe for libunwind support
    - gracefully handle SIGUSR2 without libunwind
    - integrate libunwind on-by-default (linux-x86_64) into evergreen

14 files changed, 93 insertions, 42 deletions

diff --git a/SConstruct b/SConstruct
index 007f8311205..b3cd3fa1174 100644
--- a/SConstruct
+++ b/SConstruct
@@ -505,10 +505,10 @@ add_option('msvc-debugging-format',
 )
 
 add_option('use-libunwind',
-    choices=["on", "off"],
+    choices=["on", "off", "auto"],
     const="on",
-    default="off",
-    help="Enable libunwind for backtraces (experimental)",
+    default="auto",
+    help="Enable libunwind for backtraces",
     nargs="?",
     type='choice',
 )
@@ -1018,17 +1018,6 @@ usemozjs = (jsEngine.startswith('mozjs'))
 if not serverJs and not usemozjs:
     print("Warning: --server-js=off is not needed with --js-engine=none")
 
-use_libunwind = get_option("use-libunwind") == "on"
-if use_libunwind:
-    use_system_libunwind = use_system_version_of_library("libunwind")
-    use_vendored_libunwind = not use_system_libunwind
-else:
-    if use_system_version_of_library("libunwind"):
-        print("Error: --use-system-libunwind requires --use-libunwind")
-        Exit(1)
-
-    use_system_libunwind = use_vendored_libunwind = False
-
 # We defer building the env until we have determined whether we want certain values. Some values
 # in the env actually have semantics for 'None' that differ from being absent, so it is better
 # to build it up via a dict, and then construct the Environment in one shot with kwargs.
@@ -1373,6 +1362,38 @@ link_model = get_option('link-model')
 if link_model == "auto":
     link_model = "static"
 
+# libunwind configuration.
+# In which the following globals are set and normalized to bool:
+#     - use_libunwind
+#     - use_system_libunwind
+#     - use_vendored_libunwind
+use_libunwind = get_option("use-libunwind")
+use_system_libunwind = use_system_version_of_library("libunwind")
+
+# Assume system libunwind works if it's installed and selected.
+# Vendored libunwind, however, works only on linux-x86_64.
+can_use_libunwind = (use_system_libunwind or
+    env.TargetOSIs('linux') and env['TARGET_ARCH'] == 'x86_64')
+
+if use_libunwind == "off":
+    use_libunwind = False
+    use_system_libunwind = False
+elif use_libunwind == "on":
+    use_libunwind = True
+    if not can_use_libunwind:
+        env.ConfError("libunwind not supported on target platform")
+        Exit(1)
+elif use_libunwind == "auto":
+    use_libunwind = can_use_libunwind
+
+use_vendored_libunwind = use_libunwind and not use_system_libunwind
+if use_system_libunwind and not use_libunwind:
+    print("Error: --use-system-libunwind requires --use-libunwind")
+    Exit(1)
+if use_libunwind == True:
+    env.SetConfigHeaderDefine("MONGO_CONFIG_USE_LIBUNWIND")
+
+
 # Windows can't currently support anything other than 'object' or 'static', until
 # we have both hygienic builds and have annotated functions for export.
 if env.TargetOSIs('windows') and link_model not in ['object', 'static', 'dynamic-sdk']:
diff --git a/etc/evergreen.yml b/etc/evergreen.yml
index 92f572029cf..e1b95a53fe8 100644
--- a/etc/evergreen.yml
+++ b/etc/evergreen.yml
@@ -353,7 +353,7 @@ variables:
   - enterprise-rhel-67-s390x
   - enterprise-rhel-70-64-bit
   - enterprise-rhel-70-64-bit-kitchen-sink
-  - enterprise-rhel-70-64-bit-libunwind
+  - enterprise-rhel-70-64-bit-no-libunwind
   - enterprise-rhel-71-ppc64le
   - enterprise-rhel-71-ppc64le-inmem
   - enterprise-rhel-72-s390x
@@ -8498,6 +8498,7 @@ buildvariants:
   - name: .jscore .common
   - name: jsCore_txns_large_txns_format
   - name: jsonSchema
+  - name: libunwind_tests
   - name: .logical_session_cache
   - name: .multi_shard
   - name: multi_stmt_txn_jscore_passthrough_with_migration_gen
@@ -8589,6 +8590,7 @@ buildvariants:
   - name: free_monitoring
   - name: .jscore .common
   - name: .jstestfuzz .common
+  - name: libunwind_tests
   - name: .logical_session_cache .one_sec
   - name: multiversion
   - name: replica_sets
@@ -8641,6 +8643,7 @@ buildvariants:
   - name: jsCore_auth
   - name: .jstestfuzz .common
   - name: .jstestfuzz_multiversion_gen
+  - name: libunwind_tests
   - name: .logical_session_cache .one_sec
   - name: .multiversion_fuzzer
   - name: .multiversion_passthrough
@@ -8696,6 +8699,7 @@ buildvariants:
     - ubuntu1604-build
   - name: .jscore .common
   - name: .jstestfuzz .common
+  - name: libunwind_tests
   - name: .logical_session_cache .one_sec
   - name: multiversion
   - name: .powercycle
@@ -9013,6 +9017,7 @@ buildvariants:
   - name: .encrypt !.aggregation
   - name: .jscore .common !.compat
   - name: .jstestfuzz .common
+  - name: libunwind_tests
   - name: .logical_session_cache .one_sec
   - name: noPassthrough_gen
   - name: noPassthroughWithMongod_gen
@@ -9066,6 +9071,7 @@ buildvariants:
   - name: free_monitoring
   - name: .jscore .common
   - name: .jstestfuzz .common
+  - name: libunwind_tests
   - name: .logical_session_cache .one_sec
   - name: multiversion
   - name: replica_sets
@@ -9118,6 +9124,7 @@ buildvariants:
   - name: .encrypt !.aggregation
   - name: .jscore .common !.compat
   - name: .jstestfuzz .common
+  - name: libunwind_tests
   - name: .logical_session_cache .one_sec
   - name: noPassthrough_gen
   - name: noPassthroughWithMongod_gen
@@ -9174,6 +9181,7 @@ buildvariants:
   - name: free_monitoring
   - name: .jscore .common
   - name: .jstestfuzz .common
+  - name: libunwind_tests
   - name: .logical_session_cache .one_sec
   - name: multiversion
   - name: replica_sets
@@ -9751,6 +9759,7 @@ buildvariants:
   - name: jsCore_txns_large_txns_format
   - name: jsonSchema
   - name: .jstestfuzz
+  - name: libunwind_tests
   - name: .logical_session_cache
   - name: mqlrun
   - name: .multi_shard
@@ -10155,6 +10164,7 @@ buildvariants:
     - name: jsCore_minimum_batch_size
     - name: jsCore_op_query
     - name: .jstestfuzz_multiversion_gen
+    - name: libunwind_tests
     - name: .logical_session_cache .one_sec
     - name: .multi_shard .common
     - name: multiversion
@@ -10216,6 +10226,7 @@ buildvariants:
   - name: .jscore .common !.compat !.decimal !.sharding
   - name: jsCore_txns_large_txns_format
   - name: .jstestfuzz .common
+  - name: libunwind_tests
   - name: .logical_session_cache .one_sec
   - name: .ocsp
   - name: replica_sets_auth_gen
@@ -10274,6 +10285,7 @@ buildvariants:
   - name: jsCore_txns_large_txns_format
   - name: .jstestfuzz .common
   - name: .logical_session_cache .one_sec
+  - name: libunwind_tests
   - name: replica_sets_auth_gen
   - name: replica_sets_jscore_passthrough
   - name: .replica_sets .multi_oplog
@@ -10293,17 +10305,16 @@ buildvariants:
 # This variant is to intentionally test uncommon features nightly
 - <<: *enterprise-rhel-70-64-bit-template
   name: enterprise-rhel-70-64-bit-kitchen-sink
-  display_name: "~ Enterprise RHEL 7.0 (Dagger, libunwind)"
+  display_name: "~ Enterprise RHEL 7.0 (Dagger)"
   expansions:
     <<: *enterprise-rhel-70-64-bit-expansions-template
-    compile_flags: --ssl --use-libunwind MONGO_DISTMOD=rhel70 -j$(grep -c ^processor /proc/cpuinfo) --variables-files=etc/scons/mongodbtoolchain_v3_gcc.vars
+    compile_flags: --ssl MONGO_DISTMOD=rhel70 -j$(grep -c ^processor /proc/cpuinfo) --variables-files=etc/scons/mongodbtoolchain_v3_gcc.vars
     additional_targets: dagger # If this moves to another variant, update the compile_all task
   tasks:
   - name: compile_all_run_unittests_TG
     distros:
     - rhel70
   - name: jsCore
-  - name: libunwind_tests
 
 - <<: *enterprise-rhel-70-64-bit-template
   name: hot_backups-rhel-70-64-bit
@@ -10321,13 +10332,13 @@ buildvariants:
   - name: noPassthrough_gen
 
 - <<: *enterprise-rhel-70-64-bit-template
-  name: enterprise-rhel-70-64-bit-libunwind
-  display_name: "~ Enterprise RHEL 7.0 (libunwind)"
+  name: enterprise-rhel-70-64-bit-no-libunwind
+  display_name: "~ Enterprise RHEL 7.0 (no-libunwind)"
   runs_on:
   - rhel70
   expansions:
     <<: *enterprise-rhel-70-64-bit-expansions-template
-    compile_flags: --ssl MONGO_DISTMOD=rhel70 --opt=on -j$(grep -c ^processor /proc/cpuinfo) --variables-files=etc/scons/mongodbtoolchain_v3_gcc.vars --use-libunwind
+    compile_flags: --ssl MONGO_DISTMOD=rhel70 --use-libunwind=off --opt=on -j$(grep -c ^processor /proc/cpuinfo) --variables-files=etc/scons/mongodbtoolchain_v3_gcc.vars
     has_packages: false
     mh_target: ""
   # Override list of tasks to exclude package testing and publishing
@@ -10347,7 +10358,6 @@ buildvariants:
   - name: jsCore_txns_large_txns_format
   - name: .jstestfuzz .common
   - name: .logical_session_cache .one_sec
-  - name: libunwind_tests
   - name: replica_sets_auth_gen
   - name: replica_sets_jscore_passthrough
   - name: .replica_sets .multi_oplog
diff --git a/src/mongo/SConscript b/src/mongo/SConscript
index 9774ef7e7bd..db471f1d1a9 100644
--- a/src/mongo/SConscript
+++ b/src/mongo/SConscript
@@ -56,7 +56,7 @@ env.SConscript(
 # it, and do not declare other libraries in this file.
 baseEnv = env.Clone()
 
-if use_libunwind:
+if use_libunwind == True:
     baseEnv.InjectThirdParty('unwind')
 
 stacktrace_impl_cpp = [ File('util/stacktrace_${TARGET_OS_FAMILY}.cpp') ]
@@ -307,6 +307,7 @@ config_header_substs = (
     ('@mongo_config_ssl_provider@', 'MONGO_CONFIG_SSL_PROVIDER'),
     ('@mongo_config_usdt_enabled@', 'MONGO_CONFIG_USDT_ENABLED'),
     ('@mongo_config_usdt_provider@', 'MONGO_CONFIG_USDT_PROVIDER'),
+    ('@mongo_config_use_libunwind@', 'MONGO_CONFIG_USE_LIBUNWIND'),
     ('@mongo_config_wiredtiger_enabled@', 'MONGO_CONFIG_WIREDTIGER_ENABLED'),
 )
 
diff --git a/src/mongo/config.h.in b/src/mongo/config.h.in
index c7a9e1f5fd9..54e7a14787d 100644
--- a/src/mongo/config.h.in
+++ b/src/mongo/config.h.in
@@ -89,5 +89,8 @@
 // Set to which provider defines USDT
 @mongo_config_usdt_provider@
 
+// Defined if using libunwind.
+@mongo_config_use_libunwind@
+
 // Defined if WiredTiger storage engine is enabled
 @mongo_config_wiredtiger_enabled@
diff --git a/src/mongo/util/signal_handlers.cpp b/src/mongo/util/signal_handlers.cpp
index 47582a9ae84..77a3bfa0025 100644
--- a/src/mongo/util/signal_handlers.cpp
+++ b/src/mongo/util/signal_handlers.cpp
@@ -190,7 +190,7 @@ struct LogRotationState {
 void handleOneSignal(const SignalWaitResult& waited, LogRotationState* rotation) {
     int sig = waited.sig;
     log() << "got signal " << sig << " (" << strsignal(sig) << ")";
-#ifdef __linux__
+#if defined(__linux__)
     const siginfo_t& si = waited.si;
     switch (si.si_code) {
         case SI_USER:
@@ -221,12 +221,18 @@ void handleOneSignal(const SignalWaitResult& waited, LogRotationState* rotation)
         }
         return;
     }
-#if defined(MONGO_STACKTRACE_CAN_DUMP_ALL_THREADS)
+
+#if defined(MONGO_STACKTRACE_HAS_SIGNAL)
     if (sig == stackTraceSignal()) {
+        // If there's a stackTraceSignal at all, catch it here so we don't die from it.
+        // Can dump all threads if we can, else silently ignore it.
+#if defined(MONGO_STACKTRACE_CAN_DUMP_ALL_THREADS)
         printAllThreadStacks();
+#endif
         return;
     }
 #endif
+
     // interrupt/terminate signal
     log() << "will terminate after current cmd ends";
     exitCleanly(EXIT_CLEAN);
@@ -247,8 +253,8 @@ void signalProcessingThread(LogFileStatus rotate) {
     for (int sig : kSignalProcessingThreadExclusives)
         sigaddset(&waitSignals, sig);
 
-#if defined(MONGO_STACKTRACE_CAN_DUMP_ALL_THREADS)
-    // On this thread, block the stackTraceSignal and rely on sigwaitinfo to deliver it.
+#if defined(MONGO_STACKTRACE_HAS_SIGNAL)
+    // On this thread, block the stackTraceSignal and rely on a signal wait to deliver it.
     sigaddset(&waitSignals, stackTraceSignal());
 #endif
 
@@ -297,6 +303,13 @@ void startSignalProcessingThread(LogFileStatus rotate) {
     for (int sig : kSignalProcessingThreadExclusives)
         sigaddset(&sigset, sig);
 
+#if defined(MONGO_STACKTRACE_HAS_SIGNAL) && !defined(MONGO_STACKTRACE_CAN_DUMP_ALL_THREADS)
+    // On a Unixlike build without the stacktrace behavior, we still want to handle SIGUSR2 to
+    // print a message, but it must only go to the signalProcessingThread, not on other threads.
+    // It's as if stackTraceSignal (e.g. SIGUSR2) is a member of kSignalProcessingThreadExclusives.
+    sigaddset(&sigset, stackTraceSignal());
+#endif
+
     // Mask signals in the current (only) thread. All new threads will inherit this mask.
     invariant(pthread_sigmask(SIG_SETMASK, &sigset, nullptr) == 0);
     // Spawn a thread to capture the signals we just masked off.
diff --git a/src/mongo/util/signal_handlers_synchronous.cpp b/src/mongo/util/signal_handlers_synchronous.cpp
index 86b48d46a09..be2a2bd175f 100644
--- a/src/mongo/util/signal_handlers_synchronous.cpp
+++ b/src/mongo/util/signal_handlers_synchronous.cpp
@@ -361,12 +361,10 @@ void clearSignalMask() {
 #endif
 }
 
-#ifdef __linux__
-
+#if defined(MONGO_STACKTRACE_HAS_SIGNAL)
 int stackTraceSignal() {
     return SIGUSR2;
 }
-
 #endif
 
 }  // namespace mongo
diff --git a/src/mongo/util/signal_handlers_synchronous.h b/src/mongo/util/signal_handlers_synchronous.h
index 53a5ff1fe2d..ceb513c4600 100644
--- a/src/mongo/util/signal_handlers_synchronous.h
+++ b/src/mongo/util/signal_handlers_synchronous.h
@@ -57,7 +57,11 @@ void reportOutOfMemoryErrorAndExit();
  */
 void clearSignalMask();
 
-#ifdef __linux__
+#if defined(__linux__) || defined(__APPLE__)
+#define MONGO_STACKTRACE_HAS_SIGNAL
+#endif
+
+#if defined(MONGO_STACKTRACE_HAS_SIGNAL)
 /**
  * Returns the signal used to initiate all-thread stack traces.
  */
diff --git a/src/mongo/util/stacktrace.h b/src/mongo/util/stacktrace.h
index 01a300a06a6..535199862c3 100644
--- a/src/mongo/util/stacktrace.h
+++ b/src/mongo/util/stacktrace.h
@@ -36,6 +36,7 @@
 #include <string>
 
 #include "mongo/base/string_data.h"
+#include "mongo/config.h"
 
 /**
  * All-thread backtrace is only implemented on Linux. Even on Linux, it's only AS-safe
@@ -45,7 +46,7 @@
  *    - markAsStackTraceProcessingThread
  *    - printAllThreadStacks
  */
-#if defined(__linux__) && defined(MONGO_USE_LIBUNWIND)
+#if defined(__linux__) && defined(MONGO_CONFIG_USE_LIBUNWIND)
 #define MONGO_STACKTRACE_CAN_DUMP_ALL_THREADS
 #endif
 
diff --git a/src/mongo/util/stacktrace_bm.cpp b/src/mongo/util/stacktrace_bm.cpp
index 8638e9de058..87dc3cba2b3 100644
--- a/src/mongo/util/stacktrace_bm.cpp
+++ b/src/mongo/util/stacktrace_bm.cpp
@@ -47,7 +47,7 @@
 #include "mongo/util/decimal_counter.h"
 #include "mongo/util/stacktrace.h"
 
-#if defined(MONGO_USE_LIBUNWIND)
+#if defined(MONGO_CONFIG_USE_LIBUNWIND)
 #include <libunwind.h>
 #endif
 
@@ -101,7 +101,7 @@ void BM_Print(benchmark::State& state) {
 }
 BENCHMARK(BM_Print)->Range(1, 100);
 
-#if defined(MONGO_USE_LIBUNWIND)
+#if defined(MONGO_CONFIG_USE_LIBUNWIND)
 void BM_CursorSteps(benchmark::State& state) {
     size_t items = 0;
     RecursionParam param;
@@ -134,7 +134,7 @@ void BM_CursorSteps(benchmark::State& state) {
     state.SetItemsProcessed(items);
 }
 BENCHMARK(BM_CursorSteps)->Range(1, 100);
-#endif  // MONGO_USE_LIBUNWIND
+#endif  // MONGO_CONFIG_USE_LIBUNWIND
 
 
 }  // namespace
diff --git a/src/mongo/util/stacktrace_posix.cpp b/src/mongo/util/stacktrace_posix.cpp
index ced0438ab10..5b9a409e8ab 100644
--- a/src/mongo/util/stacktrace_posix.cpp
+++ b/src/mongo/util/stacktrace_posix.cpp
@@ -55,7 +55,7 @@
 #define MONGO_STACKTRACE_BACKEND_LIBUNWIND 1
 #define MONGO_STACKTRACE_BACKEND_EXECINFO 2
 
-#if defined(MONGO_USE_LIBUNWIND)
+#if defined(MONGO_CONFIG_USE_LIBUNWIND)
 #define MONGO_STACKTRACE_BACKEND MONGO_STACKTRACE_BACKEND_LIBUNWIND
 #elif defined(MONGO_CONFIG_HAVE_EXECINFO_BACKTRACE)
 #define MONGO_STACKTRACE_BACKEND MONGO_STACKTRACE_BACKEND_EXECINFO
diff --git a/src/mongo/util/stacktrace_test.cpp b/src/mongo/util/stacktrace_test.cpp
index 441c965de00..ad82d9aa607 100644
--- a/src/mongo/util/stacktrace_test.cpp
+++ b/src/mongo/util/stacktrace_test.cpp
@@ -848,7 +848,7 @@ TEST_F(PrintAllThreadStacksTest, Go_200_Threads) {
 
 #endif  // defined(MONGO_STACKTRACE_CAN_DUMP_ALL_THREADS)
 
-#if defined(MONGO_USE_LIBUNWIND) || defined(MONGO_CONFIG_HAVE_EXECINFO_BACKTRACE)
+#if defined(MONGO_CONFIG_USE_LIBUNWIND) || defined(MONGO_CONFIG_HAVE_EXECINFO_BACKTRACE)
 /**
  * Try to backtrace from a stack containing a libc function. To do this
  * we need a libc function that makes a user-provided callback, like qsort.
diff --git a/src/mongo/util/tcmalloc_parameters.idl b/src/mongo/util/tcmalloc_parameters.idl
index 15993865720..70586cda5e3 100644
--- a/src/mongo/util/tcmalloc_parameters.idl
+++ b/src/mongo/util/tcmalloc_parameters.idl
@@ -54,7 +54,7 @@ server_parameters:
     cpp_varname: HeapProfilingEnabled
     default: false
     condition:
-      preprocessor: defined(_POSIX_VERSION) && (defined(MONGO_CONFIG_HAVE_EXECINFO_BACKTRACE) || defined(MONGO_USE_LIBUNWIND))
+      preprocessor: defined(_POSIX_VERSION) && (defined(MONGO_CONFIG_HAVE_EXECINFO_BACKTRACE) || defined(MONGO_CONFIG_USE_LIBUNWIND))
 
   heapProfilingSampleIntervalBytes:
     description: "Configure heap profiling sample interval bytes"
@@ -64,7 +64,7 @@ server_parameters:
     # 256kb
     default: 262144
     condition:
-      preprocessor: defined(_POSIX_VERSION) && (defined(MONGO_CONFIG_HAVE_EXECINFO_BACKTRACE) || defined(MONGO_USE_LIBUNWIND))
+      preprocessor: defined(_POSIX_VERSION) && (defined(MONGO_CONFIG_HAVE_EXECINFO_BACKTRACE) || defined(MONGO_CONFIG_USE_LIBUNWIND))
 
   tcmallocEnableMarkThreadTemporarilyIdle:
     description: 'REMOVED: Setting this parameter has no effect and it will be removed in a future version of MongoDB.'
diff --git a/src/third_party/SConscript b/src/third_party/SConscript
index 840c1c96601..951e100b958 100644
--- a/src/third_party/SConscript
+++ b/src/third_party/SConscript
@@ -185,12 +185,12 @@ if not use_system_version_of_library('kms-message'):
 
 if use_system_libunwind:
     thirdPartyEnvironmentModifications['unwind'] = {
-        'CPPDEFINES' : ['MONGO_USE_LIBUNWIND', 'UNW_LOCAL_ONLY'],
+        'CPPDEFINES' : ['UNW_LOCAL_ONLY'],
         'SYSLIBDEPS' : [env['LIBDEPS_UNWIND_SYSLIBDEP'], 'lzma'],
     }
 elif use_vendored_libunwind:
     thirdPartyEnvironmentModifications['unwind'] = {
-        'CPPDEFINES' : ['MONGO_USE_LIBUNWIND', 'UNW_LOCAL_ONLY'],
+        'CPPDEFINES' : ['UNW_LOCAL_ONLY'],
         'LIBDEPS' : ['$BUILD_DIR/third_party/shim_unwind'],
         'SYSLIBDEPS' : ['lzma'],
     }
diff --git a/src/third_party/unwind/SConscript b/src/third_party/unwind/SConscript
index 6b4ca0488ac..c425cdc2195 100644
--- a/src/third_party/unwind/SConscript
+++ b/src/third_party/unwind/SConscript
@@ -110,7 +110,7 @@ env.Append(
 # propagates to consumers that Inject (depend on) unwind.
 env.RegisterConsumerModifications(
     CPPPATH=[unwind_platform.Dir("install/include")],
-    CPPDEFINES=['UNW_LOCAL_ONLY', 'MONGO_USE_LIBUNWIND'],
+    CPPDEFINES=['UNW_LOCAL_ONLY'],
     LIBS=['lzma'])
 
 env.Append(