Make ProcessWatcher use kqueues on Mac.

chrome/common/process_watcher_mac.cc

+// Copyright (c) 2009 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "chrome/common/process_watcher.h"
+
+#include <errno.h>
+#include <signal.h>
+#include <sys/event.h>
+#include <sys/types.h>
+#include <sys/wait.h>
+
+#include "base/eintr_wrapper.h"
+#include "base/file_util.h"
+#include "base/time.h"
+
+namespace {
+
+// Return true if the given child is dead. This will also reap the process.
+// Doesn't block.
+bool IsChildDead(pid_t child) {
+  const pid_t result = HANDLE_EINTR(waitpid(child, NULL, WNOHANG));
+  if (result == -1) {
+    PLOG(ERROR)  << "call to waitpid() failed.";
+  } else if (result > 0) {
+    // The child has died.
+    return true;
+  }
+
+  return false;
+}
+
+// Reap |child| process.
+// This call blocks until completion.
+void BlockingReap(pid_t child) {
+  const pid_t result = HANDLE_EINTR(waitpid(child, NULL, 0));
+  if (result == -1) {
+    PLOG(ERROR) << "waitpid(" << child << ")";
+    NOTREACHED();
+  }
+}
+
+// Waits for |timeout| seconds for the given |child| to exit and reap it.
+// If the child doesn't exit within a couple of seconds, kill it.
+void WaitForChildToDie(pid_t child, unsigned timeout) {
+  int kq = HANDLE_EINTR(kqueue());
+  file_util::ScopedFD auto_close(&kq);
+  if (kq == -1) {
+    PLOG(ERROR) << "Failed to create kqueue";
+    return;
+  }
+
+  struct kevent event_to_add = {0};
+  EV_SET(&event_to_add, child, EVFILT_PROC, EV_ADD, NOTE_EXIT, 0, NULL);
+  // Register interest with kqueue.
+  int result = HANDLE_EINTR(kevent(kq, &event_to_add, 1, NULL, 0, NULL));
+  if (result == -1 && errno == ESRCH) {
+    // A "No Such Process" error is fine, the process may have died already
+    // and been reaped by someone else.
+    return;
+  }
+
+  if (result == -1) {
+    PLOG(ERROR) << "Failed to register event to listen for death of pid "
+                << child;
+    return;
+  }
+
+  struct kevent event = {0};
+
+  DCHECK(timeout != 0);
+
+  int num_processes_that_died = -1;
+  using base::Time;
+  using base::TimeDelta;
+  // We need to keep track of the elapsed time - if kevent() returns
+  // EINTR in the middle of blocking call we want to make up what's left
+  // of the timeout.
+  TimeDelta time_left = TimeDelta::FromSeconds(timeout);
+  Time wakeup = Time::Now() + time_left;
+  while(time_left.InMilliseconds() > 0) {
+    const struct timespec timeout = time_left.ToTimeSpec();
+    num_processes_that_died = kevent(kq, NULL, 0, &event, 1, &timeout);
+    if (num_processes_that_died >= 0)
+      break;
+    if (num_processes_that_died == -1 && errno == EINTR) {
+      time_left = wakeup - Time::Now();
+      continue;
+    }
+
+    // If we got here, kevent() must have returned -1.
+    PLOG(ERROR) << "kevent() failed";
+    break;
+  }
+
+  if (num_processes_that_died == -1) {
+    PLOG(ERROR) << "kevent failed";
+    return;
+  }
+  if (num_processes_that_died == 1) {
+    if (event.fflags & NOTE_EXIT &&
+        event.ident == static_cast<uintptr_t>(child)) {
+      // Process died, it's safe to make a blocking call here since the
+      // kqueue() notification occurs when the process is already zombified.
+      BlockingReap(child);
+      return;
+    } else {
+      PLOG(ERROR) << "kevent() returned unexpected result - ke.fflags ="
+                  << event.fflags
+                  << " ke.ident ="
+                  << event.ident
+                  << " while listening for pid="
+                  << child;
+    }
+  }
+
+  // If we got here the child is still alive so kill it...
+  if (kill(child, SIGKILL) == 0) {
+    // SIGKILL is uncatchable. Since the signal was delivered, we can
+    // just wait for the process to die now in a blocking manner.
+    BlockingReap(child);
+  } else {
+    PLOG(ERROR) << "While waiting for " << child << " to terminate we"
+               << " failed to deliver a SIGKILL signal";
+  }
+}
+
+}  // namespace
+
+void ProcessWatcher::EnsureProcessTerminated(base::ProcessHandle process) {
+  // If the child is already dead, then there's nothing to do.
+  if (IsChildDead(process)) {
+    return;
+  }
+  WaitForChildToDie(process, 2);
+}