POSIX: don't spawn zombies.

http://codereview.chromium.org/93147

BUG=9401


git-svn-id: svn://svn.chromium.org/chrome/trunk/src@14705 0039d316-1c4b-4281-b951-d872f2087c98

base/process_posix.cc

@@ -18,8 +18,9 @@ void Process::Terminate(int result_code) {
   // result_code isn't supportable.
   if (!process_)
     return;
-  // Wait so we clean up the zombie
-  KillProcess(process_, result_code, true);
+  // We don't wait here. It's the responsibility of other code to reap the
+  // child.
+  KillProcess(process_, result_code, false);
 }
 
 bool Process::IsProcessBackgrounded() const {

base/process_util.h

@@ -172,9 +172,13 @@ bool KillProcessById(ProcessId process_id, int exit_code, bool wait);
 #endif
 
 // Get the termination status (exit code) of the process and return true if the
-// status indicates the process crashed.  It is an error to call this if the
-// process hasn't terminated yet.
-bool DidProcessCrash(ProcessHandle handle);
+// status indicates the process crashed. |child_exited| is set to true iff the
+// child process has terminated. (|child_exited| may be NULL.)
+//
+// On Windows, it is an error to call this if the process hasn't terminated
+// yet. On POSIX, |child_exited| is set correctly since we detect terminate in
+// a different manner on POSIX.
+bool DidProcessCrash(bool* child_exited, ProcessHandle handle);
 
 // Waits for process to exit. In POSIX systems, if the process hasn't been
 // signaled then puts the exit code in |exit_code|; otherwise it's considered

base/process_util_posix.cc

@@ -56,23 +56,25 @@ ProcessId GetProcId(ProcessHandle process) {
 // entry structure.  Ignores specified exit_code; posix can't force that.
 // Returns true if this is successful, false otherwise.
 bool KillProcess(ProcessHandle process_id, int exit_code, bool wait) {
-  bool result = false;
+  bool result = kill(process_id, SIGTERM) == 0;
 
-  int status = kill(process_id, SIGTERM);
-  if (!status && wait) {
+  if (result && wait) {
     int tries = 60;
     // The process may not end immediately due to pending I/O
     while (tries-- > 0) {
-      int pid = waitpid(process_id, &status, WNOHANG);
-      if (pid == process_id) {
-        result = true;
+      int pid = waitpid(process_id, NULL, WNOHANG);
+      if (pid == process_id)
         break;
-      }
+
       sleep(1);
     }
+
+    result = kill(process_id, SIGKILL) == 0;
   }
+
   if (!result)
     DLOG(ERROR) << "Unable to terminate process.";
+
   return result;
 }
 
@@ -141,13 +143,24 @@ void RaiseProcessToHighPriority() {
   // setpriority() or sched_getscheduler, but these all require extra rights.
 }
 
-bool DidProcessCrash(ProcessHandle handle) {
+bool DidProcessCrash(bool* child_exited, ProcessHandle handle) {
   int status;
-  if (waitpid(handle, &status, WNOHANG)) {
-    // I feel like dancing!
+  const int result = waitpid(handle, &status, WNOHANG);
+  if (result == -1) {
+    LOG(ERROR) << "waitpid failed pid:" << handle << " errno:" << errno;
+    if (child_exited)
+      *child_exited = false;
+    return false;
+  } else if (result == 0) {
+    // the child hasn't exited yet.
+    if (child_exited)
+      *child_exited = false;
     return false;
   }
 
+  if (child_exited)
+    *child_exited = true;
+
   if (WIFSIGNALED(status)) {
     switch(WTERMSIG(status)) {
       case SIGSEGV:

base/process_util_win.cc

@@ -270,8 +270,12 @@ bool KillProcess(ProcessHandle process, int exit_code, bool wait) {
   return result;
 }
 
-bool DidProcessCrash(ProcessHandle handle) {
+bool DidProcessCrash(bool* child_exited, ProcessHandle handle) {
   DWORD exitcode = 0;
+
+  if (child_exited)
+    *child_exited = true;  // On Windows it an error to call this function if
+                           // the child hasn't already exited.
   if (!::GetExitCodeProcess(handle, &exitcode)) {
     NOTREACHED();
     return false;

chrome/browser/browser_main.cc

@@ -56,6 +56,7 @@
 // TODO(port): get rid of this include. It's used just to provide declarations
 // and stub definitions for classes we encouter during the porting effort.
 #include "chrome/common/temp_scaffolding_stubs.h"
+#include <signal.h>
 #endif
 
 // TODO(port): several win-only methods have been pulled out of this, but
@@ -180,6 +181,12 @@ void RunUIMessageLoop(BrowserProcess* browser_process) {
 #endif
 }
 
+#if defined(OS_POSIX)
+// See comment below, where sigaction is called.
+void SIGCHLDHandler(int signal) {
+}
+#endif
+
 }  // namespace
 
 // Main routine for running as the Browser process.
@@ -201,6 +208,14 @@ int BrowserMain(const MainFunctionParams& parameters) {
   tracked_objects::AutoTracking tracking_objects;
 #endif
 
+#if defined(OS_POSIX)
+  // We need to accept SIGCHLD, even though our handler is a no-op because
+  // otherwise we cannot wait on children. (According to POSIX 2001.)
+  struct sigaction action = {0};
+  action.sa_handler = SIGCHLDHandler;
+  CHECK(sigaction(SIGCHLD, &action, NULL) == 0);
+#endif
+
   // Do platform-specific things (such as finishing initializing Cocoa)
   // prior to instantiating the message loop. This could be turned into a
   // broadcast notification.

chrome/browser/renderer_host/browser_render_process_host.cc

@@ -668,13 +668,24 @@ void BrowserRenderProcessHost::OnChannelError() {
   DCHECK(process_.handle());
   DCHECK(channel_.get());
 
-  if (base::DidProcessCrash(process_.handle())) {
+  bool child_exited;
+  if (base::DidProcessCrash(&child_exited, process_.handle())) {
     NotificationService::current()->Notify(
         NotificationType::RENDERER_PROCESS_CRASHED,
         Source<RenderProcessHost>(this), NotificationService::NoDetails());
   }
 
-  process_.Close();
+  // POSIX: If the process crashed, then the kernel closed the socket for it
+  // and so the child has already died by the time we get here. Since
+  // DidProcessCrash called waitpid with WNOHANG, it'll reap the process.
+  // However, if DidProcessCrash didn't reap the child, we'll need to in
+  // ~BrowserRenderProcessHost via ProcessWatcher. So we can't close the handle
+  // here.
+  //
+  // This is moot on Windows where |child_exited| will always be true.
+  if (child_exited)
+    process_.Close();
+
   channel_.reset();
 
   // This process should detach all the listeners, causing the object to be

chrome/chrome.gyp

@@ -250,7 +250,8 @@
         'common/pref_names.h',
         'common/pref_service.cc',
         'common/pref_service.h',
-        'common/process_watcher.cc',
+        'common/process_watcher_posix.cc',
+        'common/process_watcher_win.cc',
         'common/process_watcher.h',
         'common/property_bag.cc',
         'common/property_bag.h',
@@ -348,7 +349,6 @@
             'common/classfactory.cc',
             'common/drag_drop_types.cc',
             'common/os_exchange_data.cc',
-            'common/process_watcher.cc',
           ],
         }],
       ],

chrome/common/child_process_host.cc

@@ -117,7 +117,7 @@ void ChildProcessHost::OnWaitableEventSignaled(base::WaitableEvent *event) {
   DCHECK(handle());
   DCHECK_EQ(object, handle());
 
-  bool did_crash = base::DidProcessCrash(object);
+  bool did_crash = base::DidProcessCrash(NULL, object);
   if (did_crash) {
     // Report that this child process crashed.
     Notify(NotificationType::CHILD_PROCESS_CRASHED);

chrome/common/common.vcproj

@@ -698,7 +698,7 @@
 			>
 		</File>
 		<File
-			RelativePath=".\process_watcher.cc"
+			RelativePath=".\process_watcher_win.cc"
 			>
 		</File>
 		<File

chrome/common/process_watcher_posix.cc

@@ -0,0 +1,79 @@
+// 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/types.h>
+#include <sys/wait.h>
+
+#include "base/platform_thread.h"
+
+// Return true if the given child is dead. This will also reap the process.
+// Doesn't block.
+static bool IsChildDead(pid_t child) {
+  const int result = waitpid(child, NULL, WNOHANG);
+  if (result == -1) {
+    NOTREACHED();
+  } else if (result > 0) {
+    // The child has died.
+    return true;
+  }
+
+  return false;
+}
+
+// A thread class which waits for the given child to exit and reaps it.
+// If the child doesn't exit within a couple of seconds, kill it.
+class BackgroundReaper : public PlatformThread::Delegate {
+ public:
+  explicit BackgroundReaper(pid_t child)
+      : child_(child) {
+  }
+
+  void ThreadMain() {
+    WaitForChildToDie();
+    delete this;
+  }
+
+  void WaitForChildToDie() {
+    // There's no good way to wait for a specific child to exit in a timed
+    // fashion. (No kqueue on Linux), so we just loop and sleep.
+
+    // Waits 0.5 * 4 = 2 seconds.
+    for (unsigned i = 0; i < 4; ++i) {
+      PlatformThread::Sleep(500);  // 0.5 seconds
+      if (IsChildDead(child_))
+        return;
+    }
+
+    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.
+      int result;
+      do {
+        result = waitpid(child_, NULL, 0);
+      } while (result == -1 && errno == EINTR);
+    } else {
+      LOG(ERROR) << "While waiting for " << child_ << " to terminate we"
+                 << " failed to deliver a SIGKILL signal (" << errno << ").";
+    }
+  }
+
+ private:
+  const pid_t child_;
+
+  DISALLOW_COPY_AND_ASSIGN(BackgroundReaper);
+};
+
+// static
+void ProcessWatcher::EnsureProcessTerminated(base::ProcessHandle process) {
+  // If the child is already dead, then there's nothing to do
+  if (IsChildDead(process))
+    return;
+
+  BackgroundReaper* reaper = new BackgroundReaper(process);
+  PlatformThread::CreateNonJoinable(0, reaper);
+}

chrome/common/temp_scaffolding_stubs.cc

@@ -225,11 +225,6 @@ LoginHandler* CreateLoginPrompt(net::AuthChallengeInfo* auth_info,
   return NULL;
 }
 
-void ProcessWatcher::EnsureProcessTerminated(int) {
-  NOTIMPLEMENTED();
-}
-
-
 //--------------------------------------------------------------------------
 
 MemoryDetails::MemoryDetails() {

chrome/test/ui/ui_test.cc

@@ -292,7 +292,18 @@ void UITest::LaunchBrowser(const CommandLine& arguments, bool clear_profile) {
   if (!homepage_.empty())
     command_line.AppendSwitchWithValue(switches::kHomePage,
                                        homepage_);
-  PathService::Get(chrome::DIR_USER_DATA, &user_data_dir_);
+#if defined(OS_POSIX)
+  const char* alternative_userdir = getenv("CHROME_UI_TESTS_USER_DATA_DIR");
+#else
+  const FilePath::StringType::value_type* const alternative_userdir = NULL;
+#endif
+
+  if (alternative_userdir) {
+    user_data_dir_ = FilePath(alternative_userdir);
+  } else {
+    PathService::Get(chrome::DIR_USER_DATA, &user_data_dir_);
+  }
+
   if (!user_data_dir_.empty())
     command_line.AppendSwitchWithValue(switches::kUserDataDir,
                                        user_data_dir_.ToWStringHack());