Index: content/common/process_watcher_mac.cc |
=================================================================== |
--- content/common/process_watcher_mac.cc (revision 111236) |
+++ content/common/process_watcher_mac.cc (working copy) |
@@ -1,170 +0,0 @@ |
-// 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 "content/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 { |
- |
-const int kWaitBeforeKillSeconds = 2; |
- |
-// 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) { |
- DPLOG(ERROR) << "waitpid(" << child << ", NULL, 0)"; |
- } |
-} |
- |
-// Waits for |timeout| seconds for the given |child| to exit and reap it. If |
-// the child doesn't exit within the time specified, kills it. |
-// |
-// This function takes two approaches: first, it tries to use kqueue to |
-// observe when the process exits. kevent can monitor a kqueue with a |
-// timeout, so this method is preferred to wait for a specified period of |
-// time. Once the kqueue indicates the process has exited, waitpid will reap |
-// the exited child. If the kqueue doesn't provide an exit event notification, |
-// before the timeout expires, or if the kqueue fails or misbehaves, the |
-// process will be mercilessly killed and reaped. |
-// |
-// A child process passed to this function may be in one of several states: |
-// running, terminated and not yet reaped, and (apparently, and unfortunately) |
-// terminated and already reaped. Normally, a process will at least have been |
-// asked to exit before this function is called, but this is not required. |
-// If a process is terminating and unreaped, there may be a window between the |
-// time that kqueue will no longer recognize it and when it becomes an actual |
-// zombie that a non-blocking (WNOHANG) waitpid can reap. This condition is |
-// detected when kqueue indicates that the process is not running and a |
-// non-blocking waitpid fails to reap the process but indicates that it is |
-// still running. In this event, a blocking attempt to reap the process |
-// collects the known-dying child, preventing zombies from congregating. |
-// |
-// In the event that the kqueue misbehaves entirely, as it might under a |
-// EMFILE condition ("too many open files", or out of file descriptors), this |
-// function will forcibly kill and reap the child without delay. This |
-// eliminates another potential zombie vector. (If you're out of file |
-// descriptors, you're probably deep into something else, but that doesn't |
-// mean that zombies be allowed to kick you while you're down.) |
-// |
-// The fact that this function seemingly can be called to wait on a child |
-// that's not only already terminated but already reaped is a bit of a |
-// problem: a reaped child's pid can be reclaimed and may refer to a distinct |
-// process in that case. The fact that this function can seemingly be called |
-// to wait on a process that's not even a child is also a problem: kqueue will |
-// work in that case, but waitpid won't, and killing a non-child might not be |
-// the best approach. |
-void WaitForChildToDie(pid_t child, int timeout) { |
- DCHECK(child > 0); |
- DCHECK(timeout > 0); |
- |
- // DON'T ADD ANY EARLY RETURNS TO THIS FUNCTION without ensuring that |
- // |child| has been reaped. Specifically, even if a kqueue, kevent, or other |
- // call fails, this function should fall back to the last resort of trying |
- // to kill and reap the process. Not observing this rule will resurrect |
- // zombies. |
- |
- int result; |
- |
- int kq = HANDLE_EINTR(kqueue()); |
- if (kq == -1) { |
- DPLOG(ERROR) << "kqueue()"; |
- } else { |
- file_util::ScopedFD auto_close_kq(&kq); |
- |
- struct kevent change = {0}; |
- EV_SET(&change, child, EVFILT_PROC, EV_ADD, NOTE_EXIT, 0, NULL); |
- result = HANDLE_EINTR(kevent(kq, &change, 1, NULL, 0, NULL)); |
- |
- if (result == -1) { |
- if (errno != ESRCH) { |
- DPLOG(ERROR) << "kevent (setup " << child << ")"; |
- } else { |
- // At this point, one of the following has occurred: |
- // 1. The process has died but has not yet been reaped. |
- // 2. The process has died and has already been reaped. |
- // 3. The process is in the process of dying. It's no longer |
- // kqueueable, but it may not be waitable yet either. Mark calls |
- // this case the "zombie death race". |
- |
- result = HANDLE_EINTR(waitpid(child, NULL, WNOHANG)); |
- |
- if (result != 0) { |
- // A positive result indicates case 1. waitpid succeeded and reaped |
- // the child. A result of -1 indicates case 2. The child has already |
- // been reaped. In both of these cases, no further action is |
- // necessary. |
- return; |
- } |
- |
- // |result| is 0, indicating case 3. The process will be waitable in |
- // short order. Fall back out of the kqueue code to kill it (for good |
- // measure) and reap it. |
- } |
- } else { |
- // Keep track of the elapsed time to be able to restart kevent if it's |
- // interrupted. |
- base::TimeDelta remaining_delta = base::TimeDelta::FromSeconds(timeout); |
- base::Time deadline = base::Time::Now() + remaining_delta; |
- result = -1; |
- struct kevent event = {0}; |
- while (remaining_delta.InMilliseconds() > 0) { |
- const struct timespec remaining_timespec = remaining_delta.ToTimeSpec(); |
- result = kevent(kq, NULL, 0, &event, 1, &remaining_timespec); |
- if (result == -1 && errno == EINTR) { |
- remaining_delta = deadline - base::Time::Now(); |
- result = 0; |
- } else { |
- break; |
- } |
- } |
- |
- if (result == -1) { |
- DPLOG(ERROR) << "kevent (wait " << child << ")"; |
- } else if (result > 1) { |
- DLOG(ERROR) << "kevent (wait " << child << "): unexpected result " |
- << result; |
- } else if (result == 1) { |
- if ((event.fflags & NOTE_EXIT) && |
- (event.ident == static_cast<uintptr_t>(child))) { |
- // The process is dead or dying. This won't block for long, if at |
- // all. |
- BlockingReap(child); |
- return; |
- } else { |
- DLOG(ERROR) << "kevent (wait " << child |
- << "): unexpected event: fflags=" << event.fflags |
- << ", ident=" << event.ident; |
- } |
- } |
- } |
- } |
- |
- // The child is still alive, or is very freshly dead. Be sure by sending it |
- // a signal. This is safe even if it's freshly dead, because it will be a |
- // zombie (or on the way to zombiedom) and kill will return 0 even if the |
- // signal is not delivered to a live process. |
- result = kill(child, SIGKILL); |
- if (result == -1) { |
- DPLOG(ERROR) << "kill(" << child << ", SIGKILL)"; |
- } else { |
- // The child is definitely on the way out now. BlockingReap won't need to |
- // wait for long, if at all. |
- BlockingReap(child); |
- } |
-} |
- |
-} // namespace |
- |
-void ProcessWatcher::EnsureProcessTerminated(base::ProcessHandle process) { |
- WaitForChildToDie(process, kWaitBeforeKillSeconds); |
-} |