runtime/platform/signal_blocker.h

// Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.

#ifndef RUNTIME_PLATFORM_SIGNAL_BLOCKER_H_
#define RUNTIME_PLATFORM_SIGNAL_BLOCKER_H_

#include "platform/assert.h"
#include "platform/globals.h"

#if defined(DART_HOST_OS_WINDOWS)
#error Do not include this file on Windows.
#endif

#include <pthread.h>
#include <signal.h>  // NOLINT

namespace dart {

class ThreadSignalBlocker {
 public:
  explicit ThreadSignalBlocker(int sig) {
    sigset_t signal_mask;
    sigemptyset(&signal_mask);
    sigaddset(&signal_mask, sig);
    // Add sig to signal mask.
    int r = pthread_sigmask(SIG_BLOCK, &signal_mask, &old);
    USE(r);
    ASSERT(r == 0);
  }

  ThreadSignalBlocker(int sigs_count, const int sigs[]) {
    sigset_t signal_mask;
    sigemptyset(&signal_mask);
    for (int i = 0; i < sigs_count; i++) {
      sigaddset(&signal_mask, sigs[i]);
    }
    // Add sig to signal mask.
    int r = pthread_sigmask(SIG_BLOCK, &signal_mask, &old);
    USE(r);
    ASSERT(r == 0);
  }

  ~ThreadSignalBlocker() {
    // Restore signal mask.
    int r = pthread_sigmask(SIG_SETMASK, &old, nullptr);
    USE(r);
    ASSERT(r == 0);
  }

 private:
  sigset_t old;
};

// The definition below is copied from Linux and adapted to avoid lint
// errors (type long int changed to intptr_t and do/while split on
// separate lines with body in {}s) and to also block signals.
#define TEMP_FAILURE_RETRY(expression)                                         \
  ({                                                                           \
    ThreadSignalBlocker tsb(SIGPROF);                                          \
    intptr_t __result;                                                         \
    do {                                                                       \
      __result = (expression);                                                 \
    } while ((__result == -1L) && (errno == EINTR));                           \
    __result;                                                                  \
  })

// This is a version of TEMP_FAILURE_RETRY which does not use the value
// returned from the expression.
#define VOID_TEMP_FAILURE_RETRY(expression)                                    \
  (static_cast<void>(TEMP_FAILURE_RETRY(expression)))

// This macro can be used to insert checks that a call is made, that
// was expected to not return EINTR, but did it anyway.
#define NO_RETRY_EXPECTED(expression)                                          \
  ({                                                                           \
    intptr_t __result = (expression);                                          \
    if (__result == -1L && errno == EINTR) {                                   \
      FATAL("Unexpected EINTR errno");                                         \
    }                                                                          \
    __result;                                                                  \
  })

#define VOID_NO_RETRY_EXPECTED(expression)                                     \
  (static_cast<void>(NO_RETRY_EXPECTED(expression)))

// Define to check in debug mode, if a signal is currently being blocked.
#define CHECK_IS_BLOCKING(signal)                                              \
  ({                                                                           \
    sigset_t signal_mask;                                                      \
    int __r = pthread_sigmask(SIG_BLOCK, nullptr, &signal_mask);               \
    USE(__r);                                                                  \
    ASSERT(__r == 0);                                                          \
    sigismember(&signal_mask, signal);                                         \
  })

// Versions of the above, that does not enter a signal blocking scope. Use only
// when a signal blocking scope is entered manually.
#define TEMP_FAILURE_RETRY_NO_SIGNAL_BLOCKER(expression)                       \
  ({                                                                           \
    intptr_t __result;                                                         \
    ASSERT(CHECK_IS_BLOCKING(SIGPROF));                                        \
    do {                                                                       \
      __result = (expression);                                                 \
    } while ((__result == -1L) && (errno == EINTR));                           \
    __result;                                                                  \
  })

#define VOID_TEMP_FAILURE_RETRY_NO_SIGNAL_BLOCKER(expression)                  \
  (static_cast<void>(TEMP_FAILURE_RETRY_NO_SIGNAL_BLOCKER(expression)))

}  // namespace dart

#endif  // RUNTIME_PLATFORM_SIGNAL_BLOCKER_H_