clang-tools-extra/clangd/support/ThreadCrashReporter.cpp

   1 //===--- ThreadCrashReporter.cpp - Thread local signal handling --*- C++-*-===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8
   9 #include "support/ThreadCrashReporter.h"
  10 #include <atomic>
  11
  12 namespace clang {
  13 namespace clangd {
  14
  15 static thread_local ThreadCrashReporter *CurrentReporter = nullptr;
  16
  17 void ThreadCrashReporter::runCrashHandlers() {
  18   // No signal handling is done here on top of what AddSignalHandler() does:
  19   // on Windows the signal handling is implmented via
  20   // SetUnhandledExceptionFilter() which is thread-directed, and on Unix
  21   // platforms the handlers are only called for KillSigs out of which only
  22   // SIGQUIT seems to be process-directed and would be delivered to any thread
  23   // that is not blocking it, but if the thread it gets delivered to has a
  24   // ThreadCrashReporter installed during the interrupt — it seems reasonable to
  25   // let it run and print the thread's context information.
  26
  27   // Call the reporters in LIFO order.
  28   ThreadCrashReporter *Reporter = CurrentReporter;
  29   while (Reporter) {
  30     Reporter->Callback();
  31     Reporter = Reporter->Next;
  32   }
  33 }
  34
  35 ThreadCrashReporter::ThreadCrashReporter(SignalCallback ThreadLocalCallback)
  36     : Callback(std::move(ThreadLocalCallback)), Next(nullptr) {
  37   this->Next = CurrentReporter;
  38   CurrentReporter = this;
  39   // Don't reorder subsequent operations: whatever comes after might crash and
  40   // we want the crash handler to see the reporter values we just set.
  41   std::atomic_signal_fence(std::memory_order_seq_cst);
  42 }
  43
  44 ThreadCrashReporter::~ThreadCrashReporter() {
  45   assert(CurrentReporter == this);
  46   CurrentReporter = this->Next;
  47   // Don't reorder subsequent operations: whatever comes after might crash and
  48   // we want the crash handler to see the reporter values we just set.
  49   std::atomic_signal_fence(std::memory_order_seq_cst);
  50 }
  51
  52 } // namespace clangd
  53 } // namespace clang