Show all system process in the task_manager.

chrome/browser/chromeos/arc/arc_process_service.cc

 // Copyright 2016 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.
 //
 // The main point of this class is to cache ARC proc nspid<->pid mapping
 // globally. Since the calculation is costly, a dedicated worker thread is
 // used. All read/write of its internal data structure (i.e., the mapping)
 // should be on this thread.
 
 #include "chrome/browser/chromeos/arc/arc_process_service.h"
 
+#include <algorithm>
 #include <queue>
 #include <set>
 #include <string>
 
+#include "base/callback.h"
 #include "base/process/process.h"
 #include "base/process/process_iterator.h"
 #include "base/task_runner_util.h"
 #include "base/trace_event/trace_event.h"
 #include "content/public/browser/browser_thread.h"
 
 namespace arc {
 
 namespace {
 
-const char kSequenceToken[] = "arc_process_service";
-
 // Weak pointer.  This class is owned by ArcServiceManager.
 ArcProcessService* g_arc_process_service = nullptr;
 
+// Matches the process name "/init" in the process tree and get the
+// corresponding process ID.
+base::ProcessId GetArcInitProcessId(
+    const base::ProcessIterator::ProcessEntries& entry_list) {
+  for (const base::ProcessEntry& entry : entry_list) {
+    // TODO(nya): Add more constraints to avoid mismatches.
+    std::string process_name =

[Luis Héctor Chávez, 2016/07/15 16:19:41]

I know you didn't write this code, but can you improve it to avoid unnecessary
allocations?

static constexpr char kInitName[] = "/init";

for (const base::ProcessEntry& entry : entry_list) {
  if (entry.cmd_line_args().empty())
    continue;
  const std::string& process_name = entry.cmd_line_args()[0];
  if (process_name == kInitName)
    return entry.pid();
}

[Hsu-Cheng, 2016/07/27 08:07:59]

Done.

+        !entry.cmd_line_args().empty() ? entry.cmd_line_args()[0] : "";
+    if (process_name == "/init") {
+      return entry.pid();
+    }
+  }
+  return base::kNullProcessId;
+}
+
+std::vector<arc::ArcProcess> GetArcSystemProcessList() {
+  std::vector<arc::ArcProcess> ret_processes;
+  const base::ProcessIterator::ProcessEntries& entry_list =
+      base::ProcessIterator(nullptr).Snapshot();
+  base::ProcessId arc_init_pid = GetArcInitProcessId(entry_list);

[cylee1, 2016/07/15 23:17:03]

nit: can be const

[Hsu-Cheng, 2016/07/27 08:07:59]

Done.

+
+  if (arc_init_pid == base::kNullProcessId) {
+    return ret_processes;
+  }
+
+  // Enumerate the child processes of ARC init for gathering ARC System
+  // Processes.
+  for (const base::ProcessEntry& entry : entry_list) {
+    // TODO(hctsai): For now, we only gather direct child process of init, need
+    //               to get the processes below. For example, installd might
+    //               fork dex2oat and it can be executed for minutes.
+    if (entry.parent_pid() == arc_init_pid) {
+      const base::ProcessId child_pid = entry.pid();
+      const base::ProcessId child_nspid =
+          base::Process(child_pid).GetPidInNamespace();
+      const std::string process_name =

[cylee1, 2016/07/15 23:17:03]

nit: can move inside the if

[Hsu-Cheng, 2016/07/27 08:07:59]

Done.

+          !entry.cmd_line_args().empty() ? entry.cmd_line_args()[0] : "";
+      if (child_nspid != base::kNullProcessId) {
+        ret_processes.emplace_back(child_nspid, child_pid, process_name,
+                                   mojom::ProcessState::PERSISTENT);
+      }
+    }
+  }
+
+  return ret_processes;
+}
+
 }  // namespace
 
 using base::kNullProcessId;
 using base::Process;
 using base::ProcessId;
 using base::SequencedWorkerPool;
 using std::map;
 using std::set;
 using std::vector;
 
 ArcProcessService::ArcProcessService(ArcBridgeService* bridge_service)
     : ArcService(bridge_service),
-      worker_pool_(new SequencedWorkerPool(1, "arc_process_manager")),
       weak_ptr_factory_(this) {
   DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
   arc_bridge_service()->process()->AddObserver(this);
   DCHECK(!g_arc_process_service);
   g_arc_process_service = this;
   // Not intended to be used from the creating thread.

[Luis Héctor Chávez, 2016/07/15 16:19:42]

Remove?

[Hsu-Cheng, 2016/07/27 08:07:59]

Done.

-  thread_checker_.DetachFromThread();
 }
 
 ArcProcessService::~ArcProcessService() {
   DCHECK(g_arc_process_service == this);
   g_arc_process_service = nullptr;
   arc_bridge_service()->process()->RemoveObserver(this);
-  worker_pool_->Shutdown();
 }
 
 // static
 ArcProcessService* ArcProcessService::Get() {
   DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
   return g_arc_process_service;
 }
 
 void ArcProcessService::OnInstanceReady() {
   DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
-  worker_pool_->PostNamedSequencedWorkerTask(
-      kSequenceToken,
+  heavy_task_runner_->PostTask(

[cylee1, 2016/07/15 23:17:03]

Are you sure SingleThreadTaskRunner work as intended in a dedicated thread? 
To me it looks like an interface and require a subclass to "implement" its real
functionality (e.g., create new thread). You can check its usage in the
"subclass" and "instantiation" section of this class on cs.chromium.org . I'm
happy to know if I were wrong.

You can use
https://cs.chromium.org/chromium/src/base/threading/platform_thread.h?rcl=0&l...
to print current thread id to verify it.

[Hsu-Cheng, 2016/07/27 08:07:59]

Done.

       FROM_HERE,
-      base::Bind(&ArcProcessService::Reset,
-                 weak_ptr_factory_.GetWeakPtr()));
+      base::Bind(&ArcProcessService::Reset, weak_ptr_factory_.GetWeakPtr()));

[Luis Héctor Chávez, 2016/07/15 16:19:41]

This is still problematic, since WeakPtrs are not designed to be used across
threads. Is there any particular reason you avoided using the solution I
proposed (having a ref-counted class that owns exclusive access to
|nspid_to_pid_|), which does not have this problem? Doing it that way will also
avoid all the (*pid_map) and inheriting from an STL container.

[cylee1, 2016/07/15 23:17:03]

To be more clear, you should not use (dereference) a WeakPtr on another thread
other than the creating thread.

[Hsu-Cheng, 2016/07/27 08:07:59]

I did move on this way. The NSPidToPidMap class is added and the methods are
bound to it.
Done.

 }
 
 void ArcProcessService::Reset() {
-  DCHECK(thread_checker_.CalledOnValidThread());
-  nspid_to_pid_.clear();
+  nspid_to_pid_->clear();

[cylee1, 2016/07/15 23:17:03]

Shouldn't we only modify the object in the dedicated thread to avoid race ?

[Hsu-Cheng, 2016/07/27 08:07:59]

Done.

 }
 
-bool ArcProcessService::RequestProcessList(
+void ArcProcessService::RequestSystemProcessList(
     RequestProcessListCallback callback) {
   DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
 
+  base::PostTaskAndReplyWithResult(heavy_task_runner_.get(), FROM_HERE,
+                                   base::Bind(&GetArcSystemProcessList),
+                                   callback);
+}
+
+bool ArcProcessService::RequestAppProcessList(
+    RequestProcessListCallback callback) {
+  DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
+
   arc::mojom::ProcessInstance* process_instance =
       arc_bridge_service()->process()->instance();
   if (!process_instance) {
     return false;
   }
   process_instance->RequestProcessList(
       base::Bind(&ArcProcessService::OnReceiveProcessList,
                  weak_ptr_factory_.GetWeakPtr(),
                  callback));
   return true;
 }
 
+// static
 void ArcProcessService::OnReceiveProcessList(
     const RequestProcessListCallback& callback,
-    mojo::Array<arc::mojom::RunningAppProcessInfoPtr> mojo_processes) {
+    mojo::Array<arc::mojom::RunningAppProcessInfoPtr> instance_processes) {
   DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
 
-  auto raw_processes = new vector<mojom::RunningAppProcessInfoPtr>();
-  mojo_processes.Swap(raw_processes);
-
-  auto ret_processes = new vector<ArcProcess>();
-  // Post to its dedicated worker thread to avoid race condition.
-  // Since no two tasks with the same token should be run at the same.
-  // Note: GetSequencedTaskRunner's shutdown behavior defaults to
-  // SKIP_ON_SHUTDOWN (ongoing task blocks shutdown).
-  // So in theory using Unretained(this) should be fine since the life cycle
-  // of |this| is the same as the main browser.
-  // To be safe I still use weak pointers, but weak_ptrs can only bind to
-  // methods without return values. That's why I can't use
-  // PostTaskAndReplyWithResult but handle the return object by myself.
-  auto runner = worker_pool_->GetSequencedTaskRunner(
-      worker_pool_->GetNamedSequenceToken(kSequenceToken));
-  runner->PostTaskAndReply(
-      FROM_HERE,
-      base::Bind(&ArcProcessService::UpdateAndReturnProcessList,
-                 weak_ptr_factory_.GetWeakPtr(),
-                 base::Owned(raw_processes),
-                 base::Unretained(ret_processes)),
-      base::Bind(&ArcProcessService::CallbackRelay,
-                 weak_ptr_factory_.GetWeakPtr(),
-                 callback,
-                 base::Owned(ret_processes)));
+  base::PostTaskAndReplyWithResult(
+      heavy_task_runner_.get(), FROM_HERE,
+      base::Bind(&ArcProcessService::UpdateAndReturnProcessList, nspid_to_pid_,
+                 base::Passed(&instance_processes)),
+      callback);
 }
 
-void ArcProcessService::CallbackRelay(
-    const RequestProcessListCallback& callback,
-    const vector<ArcProcess>* ret_processes) {
-  DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
-  callback.Run(*ret_processes);
-}
-
-void ArcProcessService::UpdateAndReturnProcessList(
-    const vector<arc::mojom::RunningAppProcessInfoPtr>* raw_processes,
-    vector<ArcProcess>* ret_processes) {
-  DCHECK(thread_checker_.CalledOnValidThread());
-
-  // Cleanup dead pids in the cache |nspid_to_pid_|.
+// static
+vector<ArcProcess> ArcProcessService::UpdateAndReturnProcessList(
+    scoped_refptr<NSPidToPidMap> pid_map,
+    mojo::Array<arc::mojom::RunningAppProcessInfoPtr> processes) {
+  // Cleanup dead pids in the cache |pid_map|.
   set<ProcessId> nspid_to_remove;
-  for (const auto& entry : nspid_to_pid_) {
+  for (const auto& entry : *pid_map) {

[cylee1, 2016/07/15 23:17:03]

I think you can create a reference to the dereferenced pointer to avoid writing
*pid_map multiple times.

[Hsu-Cheng, 2016/07/27 08:07:59]

Done.

     nspid_to_remove.insert(entry.first);
   }
   bool unmapped_nspid = false;
-  for (const auto& entry : *raw_processes) {
+  for (const auto& entry : processes) {
     // erase() returns 0 if coudln't find the key. It means a new process.
     if (nspid_to_remove.erase(entry->pid) == 0) {
-      nspid_to_pid_[entry->pid] = kNullProcessId;
+      (*pid_map)[entry->pid] = base::kNullProcessId;
       unmapped_nspid = true;
     }
   }
   for (const auto& entry : nspid_to_remove) {
-    nspid_to_pid_.erase(entry);
+    (*pid_map).erase(entry);
   }
 
   // The operation is costly so avoid calling it when possible.
   if (unmapped_nspid) {
-    UpdateNspidToPidMap();
+    UpdateNspidToPidMap(*pid_map);
   }
 
-  PopulateProcessList(raw_processes, ret_processes);
+  return FilterProcessList(*pid_map, std::move(processes));
 }
 
-void ArcProcessService::PopulateProcessList(
-    const vector<arc::mojom::RunningAppProcessInfoPtr>* raw_processes,
-    vector<ArcProcess>* ret_processes) {
-  DCHECK(thread_checker_.CalledOnValidThread());
-
-  for (const auto& entry : *raw_processes) {
-    const auto it = nspid_to_pid_.find(entry->pid);
-    // In case the process already dies so couldn't find corresponding pid.
-    if (it != nspid_to_pid_.end() && it->second != kNullProcessId) {
-      ArcProcess arc_process(entry->pid, it->second, entry->process_name,
-                             entry->process_state);
+// static
+vector<ArcProcess> ArcProcessService::FilterProcessList(
+    NSPidToPidMap& pid_map,

[cylee1, 2016/07/15 23:17:03]

const ?

[Hsu-Cheng, 2016/07/27 08:07:59]

Done.

+    mojo::Array<arc::mojom::RunningAppProcessInfoPtr> processes) {
+  vector<ArcProcess> ret_processes;
+  for (const auto& entry : processes) {
+    const auto it = pid_map.find(entry->pid);
+    if (it != pid_map.end() && it->second != base::kNullProcessId) {
+      ArcProcess arc_process(entry->pid, pid_map[entry->pid],
+                             entry->process_name, entry->process_state);
       // |entry->packages| is provided only when process.mojom's verion is >=4.
       if (entry->packages) {
         for (const auto& package : entry->packages) {
           arc_process.packages().push_back(package.get());
         }
       }
-      ret_processes->push_back(std::move(arc_process));
+      ret_processes.push_back(std::move(arc_process));
     }
   }
+  return ret_processes;
 }
 
-// Computes a map from PID in ARC namespace to PID in system namespace.
-// The returned map contains ARC processes only.
-void ArcProcessService::UpdateNspidToPidMap() {
-  DCHECK(thread_checker_.CalledOnValidThread());
-
+// static
+void ArcProcessService::UpdateNspidToPidMap(NSPidToPidMap& pid_map) {
   TRACE_EVENT0("browser", "ArcProcessService::UpdateNspidToPidMap");
 
   // NB: Despite of its name, ProcessIterator::Snapshot() may return
   // inconsistent information because it simply walks procfs. Especially
   // we must not assume the parent-child relationships are consistent.
   const base::ProcessIterator::ProcessEntries& entry_list =
       base::ProcessIterator(nullptr).Snapshot();
 
-  // System may contain many different namespaces so several different
-  // processes may have the same nspid. We need to get the proper subset of
-  // processes to create correct nspid -> pid map.
-
   // Construct the process tree.
   // NB: This can contain a loop in case of race conditions.
   map<ProcessId, vector<ProcessId> > process_tree;
   for (const base::ProcessEntry& entry : entry_list)
     process_tree[entry.parent_pid()].push_back(entry.pid());
 
-  // Find the ARC init process.
-  ProcessId arc_init_pid = kNullProcessId;
-  for (const base::ProcessEntry& entry : entry_list) {
-    // TODO(nya): Add more constraints to avoid mismatches.
-    std::string process_name =
-        !entry.cmd_line_args().empty() ? entry.cmd_line_args()[0] : "";
-    if (process_name == "/init") {
-      arc_init_pid = entry.pid();
-      break;
-    }
-  }
+  ProcessId arc_init_pid = GetArcInitProcessId(entry_list);
 
   // Enumerate all processes under ARC init and create nspid -> pid map.
   if (arc_init_pid != kNullProcessId) {
     std::queue<ProcessId> queue;
     std::set<ProcessId> visited;
     queue.push(arc_init_pid);
     while (!queue.empty()) {
       ProcessId pid = queue.front();
       queue.pop();
       // Do not visit the same process twice. Otherwise we may enter an infinite
       // loop if |process_tree| contains a loop.
       if (!visited.insert(pid).second)
         continue;
 
       ProcessId nspid = base::Process(pid).GetPidInNamespace();
 
       // All ARC processes should be in namespace so nspid is usually non-null,
       // but this can happen if the process has already gone.
       // Only add processes we're interested in (those appear as keys in
-      // |nspid_to_pid_|).
-      if (nspid != kNullProcessId &&
-          nspid_to_pid_.find(nspid) != nspid_to_pid_.end())
-        nspid_to_pid_[nspid] = pid;
+      // |pid_map|).
+      if (nspid != kNullProcessId && pid_map.find(nspid) != pid_map.end())
+        pid_map[nspid] = pid;
 
       for (ProcessId child_pid : process_tree[pid])
         queue.push(child_pid);
     }
   }
 }
 
 }  // namespace arc