Update upstream source from tag 'upstream/6.0.0'master

Update to upstream version '6.0.0'
with Debian dir 5604a80ec1c96ca76f25f40d78e6ef855abec322

1 files changed, 116 insertions, 125 deletions

diff --git a/src/mongo/util/concurrency/thread_name.cpp b/src/mongo/util/concurrency/thread_name.cpp
index 5109b079c6d..1a950c24bfa 100644
--- a/src/mongo/util/concurrency/thread_name.cpp
+++ b/src/mongo/util/concurrency/thread_name.cpp
@@ -44,6 +44,10 @@
 #include <mach/thread_info.h>
 #endif
 #endif
+#if defined(__linux__)
+#include <sys/syscall.h>
+#include <sys/types.h>
+#endif
 
 #include <fmt/format.h>
 
@@ -51,18 +55,13 @@
 #include "mongo/config.h"
 #include "mongo/logv2/log.h"
 #include "mongo/platform/atomic_word.h"
-#include "mongo/platform/process_id.h"
-#include "mongo/util/thread_context.h"
+#include "mongo/util/str.h"
 
 namespace mongo {
 using namespace fmt::literals;
 
 namespace {
 
-bool isMainThread() {
-    return ProcessId::getCurrent() == ProcessId::getCurrentThreadId();
-}
-
 #ifdef _WIN32
 // From https://msdn.microsoft.com/en-us/library/xcb2z8hs.aspx
 // Note: The thread name is only set for the thread if the debugger is attached.
@@ -93,15 +92,49 @@ void setWindowsThreadName(DWORD dwThreadID, const char* threadName) {
 }
 #endif
 
-void setOSThreadName(const std::string& threadName) {
+constexpr auto kMainId = size_t{0};
+
+auto makeAnonymousThreadName() {
+    static auto gNextAnonymousId = AtomicWord<size_t>{kMainId};
+    auto id = gNextAnonymousId.fetchAndAdd(1);
+    if (id == kMainId) {
+        // The first thread name should always be "main".
+        return make_intrusive<ThreadName>("main");
+    } else {
+        return make_intrusive<ThreadName>("thread{}"_format(id));
+    }
+}
+
+struct ThreadNameSconce {
+    ThreadNameSconce() : cachedPtr(makeAnonymousThreadName()) {
+        // Note that we're not setting the thread name here. It will log differently, but appear the
+        // same in top and like.
+    }
+
+    // At any given time, either cachedPtr or activePtr can be valid, but not both.
+    boost::intrusive_ptr<ThreadName> activePtr;
+    boost::intrusive_ptr<ThreadName> cachedPtr;
+};
+
+auto getSconce = ThreadContext::declareDecoration<ThreadNameSconce>();
+auto& getThreadName(const boost::intrusive_ptr<ThreadContext>& context) {
+    auto& sconce = getSconce(context.get());
+    if (sconce.activePtr) {
+        return sconce.activePtr;
+    }
+
+    return sconce.cachedPtr;
+}
+
+void setOSThreadName(StringData threadName) {
 #if defined(_WIN32)
     // Naming should not be expensive compared to thread creation and connection set up, but if
     // testing shows otherwise we should make this depend on DEBUG again.
-    setWindowsThreadName(GetCurrentThreadId(), threadName.c_str());
+    setWindowsThreadName(GetCurrentThreadId(), threadName.rawData());
 #elif defined(__APPLE__)
     // Maximum thread name length on OS X is MAXTHREADNAMESIZE (64 characters). This assumes
     // OS X 10.6 or later.
-    std::string threadNameCopy = threadName;
+    std::string threadNameCopy = threadName.toString();
     if (threadNameCopy.size() > MAXTHREADNAMESIZE) {
         threadNameCopy.resize(MAXTHREADNAMESIZE - 4);
         threadNameCopy += "...";
@@ -117,137 +150,95 @@ void setOSThreadName(const std::string& threadName) {
     // Do not set thread name on the main() thread. Setting the name on main thread breaks
     // pgrep/pkill since these programs base this name on /proc/*/status which displays the thread
     // name, not the executable name.
-    if (isMainThread())
-        return;
-    //  Maximum thread name length supported on Linux is 16 including the null terminator.
-    //  Ideally we use short and descriptive thread names that fit: this helps for log
-    //  readability as well. Still, as the limit is so low and a few current names exceed the
-    //  limit, it's best to shorten long names.
-    static constexpr size_t kMaxThreadNameLength = 16 - 1;
-    boost::optional<std::string> shortNameBuf;
-    const char* truncName = threadName.c_str();
-    if (threadName.size() > kMaxThreadNameLength) {
-        StringData sd = threadName;
-        shortNameBuf = "{}.{}"_format(sd.substr(0, 7), sd.substr(sd.size() - 7));
-        truncName = shortNameBuf->c_str();
-    }
-
-    int error = pthread_setname_np(pthread_self(), truncName);
-    if (error) {
-        LOGV2(23103,
-              "Ignoring error from setting thread name: {error}",
-              "Ignoring error from setting thread name",
-              "error"_attr = errnoWithDescription(error));
+    if (getpid() != syscall(SYS_gettid)) {
+        //  Maximum thread name length supported on Linux is 16 including the null terminator.
+        //  Ideally we use short and descriptive thread names that fit: this helps for log
+        //  readability as well. Still, as the limit is so low and a few current names exceed the
+        //  limit, it's best to shorten long names.
+        int error = 0;
+        if (threadName.size() > 15) {
+            std::string shortName = str::stream()
+                << threadName.substr(0, 7) << '.' << threadName.substr(threadName.size() - 7);
+            error = pthread_setname_np(pthread_self(), shortName.c_str());
+        } else {
+            error = pthread_setname_np(pthread_self(), threadName.rawData());
+        }
+
+        if (error) {
+            LOGV2(23103,
+                  "Ignoring error from setting thread name: {error}",
+                  "Ignoring error from setting thread name",
+                  "error"_attr = errnoWithDescription(error));
+        }
     }
 #endif
 }
 
-/**
- * Manages the relationship of our high-level ThreadNameRef strings to
- * the thread local context, and efficiently notifying the OS of name
- * changes. We try to apply temporary names to threads to make them
- * meaningful representations of the kind of work the thread is doing.
- * But sharing these names with the OS is slow and name length is limited.  So
- * ThreadNameInfo is an auxiliary resource to the OS thread name, available to
- * the LOGV2 system and to GDB.
- *
- * ThreadNameInfo is a decoration of ThreadContext.
- * ThreadContext are held by thread_local storage and so threads started
- * after server initialization will have an associated ThreadNameInfo.
- *
- * A name is "active" when it has been pushed to the OS by `setHandle`. The
- * association can be abandoned by calling `release`. This doesn't affect the
- * OS, but indicates that the name binding is abandoned and shouldn't be
- * preserved by returning it from subsequent `setHandle` calls. We do however
- * retain the inactive reference in hopes of perhaps identifying redundant
- * `setHandle` calls that would set the OS thread name to the same value it
- * already has.
- *
- * Upon construction, a ThreadNameInfo has an inactive unique name that
- * the OS doesn't know about yet. A push/pop style call sequence of
- * `h=getHandle()` then (eventually) `setHandle(h)` can make this name
- * the active (known to the OS) thread name.
- */
-class ThreadNameInfo {
-public:
-    /** Returns the thread name ref, whether it's active or not. */
-    const ThreadNameRef& getHandle() const {
-        return _h;
-    }
+}  // namespace
 
-    /**
-     * Changes the thread name ref to `name`, marking it active,
-     * and updating the OS thread name if necessary.
-     *
-     * If there was a previous active thread name, it is returned so that
-     * callers can perhaps restore it and implement a temporary rename.
-     * Inactive thread names are considered abandoned and are not returned.
-     */
-    ThreadNameRef setHandle(ThreadNameRef name) {
-        bool alreadyActive = std::exchange(_active, true);
-        if (name == _h)
-            return {};
-        auto old = std::exchange(_h, std::move(name));
-        setOSThreadName(*_h);
-        if (alreadyActive)
-            return old;
-        return {};
-    }
+ThreadName::Id ThreadName::_nextId() {
+    static auto gNextId = AtomicWord<Id>{0};
+    return gNextId.fetchAndAdd(1);
+}
 
-    /**
-     * Mark the current ThreadNameRef as inactive. This is only a marking and
-     * does not affect the OS thread name. The ThreadNameRef is retained
-     * so that redundant setHandle calls can be recognized and elided.
-     */
-    void release() {
-        _active = false;
+StringData ThreadName::getStaticString() {
+    auto& context = ThreadContext::get();
+    if (!context) {
+        // Use a static fallback to avoid allocations. This is the string that will be used before
+        // initializers run in main a.k.a. pre-init.
+        static constexpr auto kFallback = "-"_sd;
+        return kFallback;
     }
 
-    /**
-     * Get a pointer to this thread's ThreadNameInfo.
-     * Returns null if there's no ThreadContext to get it from.
-     */
-    static ThreadNameInfo* forThisThread() {
-        auto& context = ThreadContext::get();
-        return context ? &_decoration(*context) : nullptr;
-    }
+    return getThreadName(context)->toString();
+}
 
-private:
-    inline static auto _decoration = ThreadContext::declareDecoration<ThreadNameInfo>();
-
-    /**
-     * Main thread always gets "main". Other threads are sequentially
-     * named as "thread1", "thread2", etc.
-     */
-    static std::string _makeAnonymousThreadName() {
-        if (isMainThread())
-            return "main";
-        static AtomicWord<uint64_t> next{1};
-        return "thread{}"_format(next.fetchAndAdd(1));
-    }
+boost::intrusive_ptr<ThreadName> ThreadName::get(boost::intrusive_ptr<ThreadContext> context) {
+    return getThreadName(context);
+}
 
-    ThreadNameRef _h{_makeAnonymousThreadName()};
-    bool _active = false;
-};
+boost::intrusive_ptr<ThreadName> ThreadName::set(boost::intrusive_ptr<ThreadContext> context,
+                                                 boost::intrusive_ptr<ThreadName> name) {
+    invariant(name);
 
-}  // namespace
+    auto& sconce = getSconce(context.get());
 
-ThreadNameRef getThreadNameRef() {
-    if (auto info = ThreadNameInfo::forThisThread())
-        return info->getHandle();
-    return {};
-}
+    if (sconce.activePtr) {
+        invariant(!sconce.cachedPtr);
+        if (*sconce.activePtr == *name) {
+            // The name was already set, skip setting it to the OS thread name.
+            return {};
+        } else {
+            // Replace the current active name with the new one, and set the OS thread name.
+            setOSThreadName(name->toString());
+            return std::exchange(sconce.activePtr, name);
+        }
+    } else if (sconce.cachedPtr) {
+        if (*sconce.cachedPtr == *name) {
+            // The name was cached, set it as active and skip setting it to the OS thread name.
+            sconce.activePtr = std::exchange(sconce.cachedPtr, {});
+            return {};
+        } else {
+            // The new name is different than the cached name, set the active, reset the cached, and
+            // set the OS thread name.
+            setOSThreadName(name->toString());
 
-ThreadNameRef setThreadNameRef(ThreadNameRef name) {
-    invariant(name);
-    if (auto info = ThreadNameInfo::forThisThread())
-        return info->setHandle(std::move(name));
-    return {};
+            sconce.activePtr = name;
+            sconce.cachedPtr.reset();
+            return {};
+        }
+    }
+
+    MONGO_UNREACHABLE;
 }
 
-void releaseThreadNameRef() {
-    if (auto info = ThreadNameInfo::forThisThread())
-        info->release();
+void ThreadName::release(boost::intrusive_ptr<ThreadContext> context) {
+    auto& sconce = getSconce(context.get());
+    if (sconce.activePtr) {
+        sconce.cachedPtr = std::exchange(sconce.activePtr, {});
+    }
 }
 
+ThreadName::ThreadName(StringData name) : _id(_nextId()), _storage(name.toString()){};
+
 }  // namespace mongo