third_party/perfetto/src/trace_processor/importers/common/process_tracker.cc

/*
 * Copyright (C) 2018 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#include "src/trace_processor/importers/common/process_tracker.h"
#include "src/trace_processor/storage/stats.h"

#include <cinttypes>
#include <utility>

namespace perfetto {
namespace trace_processor {

ProcessTracker::ProcessTracker(TraceProcessorContext* context)
    : context_(context), args_tracker_(context) {
  // Reserve utid/upid 0. These are special as embedders (e.g. Perfetto UI)
  // exclude them from certain views (e.g. thread state) under the assumption
  // that they correspond to the idle (swapper) process. When parsing Linux
  // system traces, SetPidZeroIsUpidZeroIdleProcess will be called to associate
  // tid0/pid0 to utid0/upid0. If other types of traces refer to tid0/pid0,
  // then they will get their own non-zero utid/upid, so that those threads are
  // still surfaced in embedder UIs.
  tables::ThreadTable::Row thread_row;
  thread_row.tid = 0u;
  thread_row.upid = 0u;
  thread_row.is_main_thread = true;
  context_->storage->mutable_thread_table()->Insert(thread_row);

  tables::ProcessTable::Row process_row;
  process_row.pid = 0u;
  context_->storage->mutable_process_table()->Insert(process_row);

  // An element to match the reserved tid = 0.
  thread_name_priorities_.push_back(ThreadNamePriority::kOther);
}

ProcessTracker::~ProcessTracker() = default;

UniqueTid ProcessTracker::StartNewThread(std::optional<int64_t> timestamp,
                                         uint32_t tid) {
  tables::ThreadTable::Row row;
  row.tid = tid;
  row.start_ts = timestamp;

  auto* thread_table = context_->storage->mutable_thread_table();
  UniqueTid new_utid = thread_table->Insert(row).row;
  tids_[tid].emplace_back(new_utid);
  PERFETTO_DCHECK(thread_name_priorities_.size() == new_utid);
  thread_name_priorities_.push_back(ThreadNamePriority::kOther);
  return new_utid;
}

void ProcessTracker::EndThread(int64_t timestamp, uint32_t tid) {
  auto* thread_table = context_->storage->mutable_thread_table();
  auto* process_table = context_->storage->mutable_process_table();

  // Don't bother creating a new thread if we're just going to
  // end it straight away.
  //
  // This is useful in situations where we get a sched_process_free event for a
  // worker thread in a process *after* the main thread finishes - in that case
  // we would have already ended the process and we don't want to
  // create a new thread here (see b/193520421 for an example of a trace
  // where this happens in practice).
  std::optional<UniqueTid> opt_utid = GetThreadOrNull(tid);
  if (!opt_utid)
    return;

  UniqueTid utid = *opt_utid;
  thread_table->mutable_end_ts()->Set(utid, timestamp);

  // Remove the thread from the list of threads being tracked as any event after
  // this one should be ignored.
  auto& vector = tids_[tid];
  vector.erase(std::remove(vector.begin(), vector.end(), utid));

  auto opt_upid = thread_table->upid()[utid];
  if (!opt_upid.has_value() || process_table->pid()[*opt_upid] != tid)
    return;

  // If the process pid and thread tid are equal then, as is the main thread
  // of the process, we should also finish the process itself.
  PERFETTO_DCHECK(thread_table->is_main_thread()[utid].value());
  process_table->mutable_end_ts()->Set(*opt_upid, timestamp);
  pids_.Erase(tid);
}

std::optional<UniqueTid> ProcessTracker::GetThreadOrNull(uint32_t tid) {
  auto opt_utid = GetThreadOrNull(tid, std::nullopt);
  if (!opt_utid)
    return std::nullopt;

  auto* threads = context_->storage->mutable_thread_table();
  UniqueTid utid = *opt_utid;

  // Ensure that the tid matches the tid we were looking for.
  PERFETTO_DCHECK(threads->tid()[utid] == tid);

  // If the thread is being tracked by the process tracker, it should not be
  // known to have ended.
  PERFETTO_DCHECK(!threads->end_ts()[utid].has_value());

  return utid;
}

UniqueTid ProcessTracker::GetOrCreateThread(uint32_t tid) {
  auto utid = GetThreadOrNull(tid);
  return utid ? *utid : StartNewThread(std::nullopt, tid);
}

UniqueTid ProcessTracker::UpdateThreadName(uint32_t tid,
                                           StringId thread_name_id,
                                           ThreadNamePriority priority) {
  auto utid = GetOrCreateThread(tid);
  UpdateThreadNameByUtid(utid, thread_name_id, priority);
  return utid;
}

void ProcessTracker::UpdateThreadNameByUtid(UniqueTid utid,
                                            StringId thread_name_id,
                                            ThreadNamePriority priority) {
  if (thread_name_id.is_null())
    return;

  auto* thread_table = context_->storage->mutable_thread_table();
  if (priority >= thread_name_priorities_[utid]) {
    thread_table->mutable_name()->Set(utid, thread_name_id);
    thread_name_priorities_[utid] = priority;
  }
}

bool ProcessTracker::IsThreadAlive(UniqueTid utid) {
  auto* threads = context_->storage->mutable_thread_table();
  auto* processes = context_->storage->mutable_process_table();

  // If the thread has an end ts, it's certainly dead.
  if (threads->end_ts()[utid].has_value())
    return false;

  // If we don't know the parent process, we have to consider this thread alive.
  auto opt_current_upid = threads->upid()[utid];
  if (!opt_current_upid)
    return true;

  // If the process is already dead, the thread can't be alive.
  UniquePid current_upid = *opt_current_upid;
  if (processes->end_ts()[current_upid].has_value())
    return false;

  // If the process has been replaced in |pids_|, this thread is dead.
  uint32_t current_pid = processes->pid()[current_upid];
  auto pid_it = pids_.Find(current_pid);
  if (pid_it && *pid_it != current_upid)
    return false;

  return true;
}

std::optional<UniqueTid> ProcessTracker::GetThreadOrNull(
    uint32_t tid,
    std::optional<uint32_t> pid) {
  auto* threads = context_->storage->mutable_thread_table();
  auto* processes = context_->storage->mutable_process_table();

  auto vector_it = tids_.Find(tid);
  if (!vector_it)
    return std::nullopt;

  // Iterate backwards through the threads so ones later in the trace are more
  // likely to be picked.
  const auto& vector = *vector_it;
  for (auto it = vector.rbegin(); it != vector.rend(); it++) {
    UniqueTid current_utid = *it;

    // If we finished this thread, we should have removed it from the vector
    // entirely.
    PERFETTO_DCHECK(!threads->end_ts()[current_utid].has_value());

    // If the thread is dead, ignore it.
    if (!IsThreadAlive(current_utid))
      continue;

    // If we don't know the parent process, we have to choose this thread.
    auto opt_current_upid = threads->upid()[current_utid];
    if (!opt_current_upid)
      return current_utid;

    // We found a thread that matches both the tid and its parent pid.
    uint32_t current_pid = processes->pid()[*opt_current_upid];
    if (!pid || current_pid == *pid)
      return current_utid;
  }
  return std::nullopt;
}

UniqueTid ProcessTracker::UpdateThread(uint32_t tid, uint32_t pid) {
  auto* thread_table = context_->storage->mutable_thread_table();

  // Try looking for a thread that matches both tid and thread group id (pid).
  std::optional<UniqueTid> opt_utid = GetThreadOrNull(tid, pid);

  // If no matching thread was found, create a new one.
  UniqueTid utid = opt_utid ? *opt_utid : StartNewThread(std::nullopt, tid);
  PERFETTO_DCHECK(thread_table->tid()[utid] == tid);

  // Find matching process or create new one.
  if (!thread_table->upid()[utid].has_value()) {
    AssociateThreadToProcess(utid, GetOrCreateProcess(pid));
  }

  ResolvePendingAssociations(utid, *thread_table->upid()[utid]);

  return utid;
}

void ProcessTracker::UpdateTrustedPid(uint32_t trusted_pid, uint64_t uuid) {
  trusted_pids_[uuid] = trusted_pid;
}

std::optional<uint32_t> ProcessTracker::GetTrustedPid(uint64_t uuid) {
  if (trusted_pids_.find(uuid) == trusted_pids_.end())
    return std::nullopt;
  return trusted_pids_[uuid];
}

std::optional<uint32_t> ProcessTracker::ResolveNamespacedTid(
    uint32_t root_level_pid,
    uint32_t tid) {
  if (root_level_pid <= 0)  // Not a valid pid.
    return std::nullopt;

  // If the process doesn't run in a namespace (or traced_probes doesn't observe
  // that), return std::nullopt as failure to resolve.
  auto process_it = namespaced_processes_.find(root_level_pid);
  if (process_it == namespaced_processes_.end())
    return std::nullopt;

  // Check if it's the main thread.
  const auto& process = process_it->second;
  auto ns_level = process.nspid.size() - 1;
  auto pid_local = process.nspid.back();
  if (pid_local == tid)
    return root_level_pid;

  // Check if any non-main thread has a matching ns-local thread ID.
  for (const auto& root_level_tid : process.threads) {
    const auto& thread = namespaced_threads_[root_level_tid];
    PERFETTO_DCHECK(thread.nstid.size() > ns_level);
    auto tid_ns_local = thread.nstid[ns_level];
    if (tid_ns_local == tid)
      return thread.tid;
  }

  // Failed to resolve or the thread isn't namespaced
  return std::nullopt;
}

UniquePid ProcessTracker::StartNewProcess(std::optional<int64_t> timestamp,
                                          std::optional<uint32_t> parent_tid,
                                          uint32_t pid,
                                          StringId main_thread_name,
                                          ThreadNamePriority priority) {
  pids_.Erase(pid);
  // TODO(eseckler): Consider erasing all old entries in |tids_| that match the
  // |pid| (those would be for an older process with the same pid). Right now,
  // we keep them in |tids_| (if they weren't erased by EndThread()), but ignore
  // them in GetThreadOrNull().

  // Create a new UTID for the main thread, so we don't end up reusing an old
  // entry in case of TID recycling.
  UniqueTid utid = StartNewThread(timestamp, /*tid=*/pid);
  UpdateThreadNameByUtid(utid, main_thread_name, priority);

  // Note that we erased the pid above so this should always return a new
  // process.
  UniquePid upid = GetOrCreateProcess(pid);

  auto* process_table = context_->storage->mutable_process_table();
  auto* thread_table = context_->storage->mutable_thread_table();

  PERFETTO_DCHECK(!process_table->name()[upid].has_value());
  PERFETTO_DCHECK(!process_table->start_ts()[upid].has_value());

  if (timestamp) {
    process_table->mutable_start_ts()->Set(upid, *timestamp);
  }
  process_table->mutable_name()->Set(upid, main_thread_name);

  if (parent_tid) {
    UniqueTid parent_utid = GetOrCreateThread(*parent_tid);
    auto opt_parent_upid = thread_table->upid()[parent_utid];
    if (opt_parent_upid.has_value()) {
      process_table->mutable_parent_upid()->Set(upid, *opt_parent_upid);
    } else {
      pending_parent_assocs_.emplace_back(parent_utid, upid);
    }
  }
  return upid;
}

UniquePid ProcessTracker::SetProcessMetadata(uint32_t pid,
                                             std::optional<uint32_t> ppid,
                                             base::StringView name,
                                             base::StringView cmdline) {
  std::optional<UniquePid> pupid;
  if (ppid.has_value()) {
    pupid = GetOrCreateProcess(ppid.value());
  }

  UniquePid upid = GetOrCreateProcess(pid);
  auto* process_table = context_->storage->mutable_process_table();

  StringId proc_name_id = context_->storage->InternString(name);
  process_table->mutable_name()->Set(upid, proc_name_id);
  process_table->mutable_cmdline()->Set(
      upid, context_->storage->InternString(cmdline));
  if (pupid)
    process_table->mutable_parent_upid()->Set(upid, *pupid);

  return upid;
}

void ProcessTracker::SetProcessUid(UniquePid upid, uint32_t uid) {
  auto* process_table = context_->storage->mutable_process_table();
  process_table->mutable_uid()->Set(upid, uid);

  // The notion of the app ID (as derived from the uid) is defined in
  // frameworks/base/core/java/android/os/UserHandle.java
  process_table->mutable_android_appid()->Set(upid, uid % 100000);
}

void ProcessTracker::SetProcessNameIfUnset(UniquePid upid,
                                           StringId process_name_id) {
  auto* process_table = context_->storage->mutable_process_table();
  if (!process_table->name()[upid].has_value())
    process_table->mutable_name()->Set(upid, process_name_id);
}

void ProcessTracker::SetStartTsIfUnset(UniquePid upid,
                                       int64_t start_ts_nanoseconds) {
  auto* process_table = context_->storage->mutable_process_table();
  if (!process_table->start_ts()[upid].has_value())
    process_table->mutable_start_ts()->Set(upid, start_ts_nanoseconds);
}

void ProcessTracker::UpdateThreadNameAndMaybeProcessName(
    uint32_t tid,
    StringId thread_name,
    ThreadNamePriority priority) {
  auto* thread_table = context_->storage->mutable_thread_table();
  auto* process_table = context_->storage->mutable_process_table();

  UniqueTid utid = UpdateThreadName(tid, thread_name, priority);
  std::optional<UniquePid> opt_upid = thread_table->upid()[utid];
  if (opt_upid.has_value() && process_table->pid()[*opt_upid] == tid) {
    PERFETTO_DCHECK(thread_table->is_main_thread()[utid]);
    process_table->mutable_name()->Set(*opt_upid, thread_name);
  }
}

UniquePid ProcessTracker::GetOrCreateProcess(uint32_t pid) {
  auto* process_table = context_->storage->mutable_process_table();

  // If the insertion succeeds, we'll fill the upid below.
  auto it_and_ins = pids_.Insert(pid, UniquePid{0});
  if (!it_and_ins.second) {
    // Ensure that the process has not ended.
    PERFETTO_DCHECK(!process_table->end_ts()[*it_and_ins.first].has_value());
    return *it_and_ins.first;
  }

  tables::ProcessTable::Row row;
  row.pid = pid;

  UniquePid upid = process_table->Insert(row).row;
  *it_and_ins.first = upid;  // Update the newly inserted hashmap entry.

  // Create an entry for the main thread.
  // We cannot call StartNewThread() here, because threads for this process
  // (including the main thread) might have been seen already prior to this
  // call. This call usually comes from the ProcessTree dump which is delayed.
  UpdateThread(/*tid=*/pid, pid);
  return upid;
}

void ProcessTracker::AssociateThreads(UniqueTid utid1, UniqueTid utid2) {
  auto* tt = context_->storage->mutable_thread_table();

  // First of all check if one of the two threads is already bound to a process.
  // If that is the case, map the other thread to the same process and resolve
  // recursively any associations pending on the other thread.

  auto opt_upid1 = tt->upid()[utid1];
  auto opt_upid2 = tt->upid()[utid2];

  if (opt_upid1.has_value() && !opt_upid2.has_value()) {
    AssociateThreadToProcess(utid2, *opt_upid1);
    ResolvePendingAssociations(utid2, *opt_upid1);
    return;
  }

  if (opt_upid2.has_value() && !opt_upid1.has_value()) {
    AssociateThreadToProcess(utid1, *opt_upid2);
    ResolvePendingAssociations(utid1, *opt_upid2);
    return;
  }

  if (opt_upid1.has_value() && opt_upid1 != opt_upid2) {
    // Cannot associate two threads that belong to two different processes.
    PERFETTO_ELOG("Process tracker failure. Cannot associate threads %u, %u",
                  tt->tid()[utid1], tt->tid()[utid2]);
    context_->storage->IncrementStats(stats::process_tracker_errors);
    return;
  }

  pending_assocs_.emplace_back(utid1, utid2);
}

void ProcessTracker::ResolvePendingAssociations(UniqueTid utid_arg,
                                                UniquePid upid) {
  auto* tt = context_->storage->mutable_thread_table();
  auto* pt = context_->storage->mutable_process_table();
  PERFETTO_DCHECK(tt->upid()[utid_arg] == upid);

  std::vector<UniqueTid> resolved_utids;
  resolved_utids.emplace_back(utid_arg);

  while (!resolved_utids.empty()) {
    UniqueTid utid = resolved_utids.back();
    resolved_utids.pop_back();
    for (auto it = pending_parent_assocs_.begin();
         it != pending_parent_assocs_.end();) {
      UniqueTid parent_utid = it->first;
      UniquePid child_upid = it->second;

      if (parent_utid != utid) {
        ++it;
        continue;
      }
      PERFETTO_DCHECK(child_upid != upid);

      // Set the parent pid of the other process
      PERFETTO_DCHECK(!pt->parent_upid()[child_upid] ||
                      pt->parent_upid()[child_upid] == upid);
      pt->mutable_parent_upid()->Set(child_upid, upid);

      // Erase the pair. The |pending_parent_assocs_| vector is not sorted and
      // swapping a std::pair<uint32_t, uint32_t> is cheap.
      std::swap(*it, pending_parent_assocs_.back());
      pending_parent_assocs_.pop_back();
    }

    auto end = pending_assocs_.end();
    for (auto it = pending_assocs_.begin(); it != end;) {
      UniqueTid other_utid;
      if (it->first == utid) {
        other_utid = it->second;
      } else if (it->second == utid) {
        other_utid = it->first;
      } else {
        ++it;
        continue;
      }

      PERFETTO_DCHECK(other_utid != utid);

      // Update the other thread and associated it to the same process.
      PERFETTO_DCHECK(!tt->upid()[other_utid] ||
                      tt->upid()[other_utid] == upid);
      AssociateThreadToProcess(other_utid, upid);

      // Swap the current element to the end of the list and move the end
      // iterator back. This works because |pending_assocs_| is not sorted. We
      // do it this way rather than modifying |pending_assocs_| directly to
      // prevent undefined behaviour caused by modifying a vector while
      // iterating through it.
      std::swap(*it, *(--end));

      // Recurse into the newly resolved thread. Some other threads might have
      // been bound to that.
      resolved_utids.emplace_back(other_utid);
    }

    // Make sure to actually erase the utids which have been resolved.
    pending_assocs_.erase(end, pending_assocs_.end());
  }  // while (!resolved_utids.empty())
}

void ProcessTracker::AssociateThreadToProcess(UniqueTid utid, UniquePid upid) {
  auto* thread_table = context_->storage->mutable_thread_table();
  thread_table->mutable_upid()->Set(utid, upid);
  auto* process_table = context_->storage->mutable_process_table();
  bool main_thread = thread_table->tid()[utid] == process_table->pid()[upid];
  thread_table->mutable_is_main_thread()->Set(utid, main_thread);
}

void ProcessTracker::SetPidZeroIsUpidZeroIdleProcess() {
  // Create a mapping from (t|p)id 0 -> u(t|p)id 0 for the idle process.
  tids_.Insert(0, std::vector<UniqueTid>{0});
  pids_.Insert(0, UniquePid{0});

  auto swapper_id = context_->storage->InternString("swapper");
  UpdateThreadName(0, swapper_id, ThreadNamePriority::kTraceProcessorConstant);
}

ArgsTracker::BoundInserter ProcessTracker::AddArgsTo(UniquePid upid) {
  return args_tracker_.AddArgsTo(upid);
}

void ProcessTracker::NotifyEndOfFile() {
  args_tracker_.Flush();
  tids_.Clear();
  pids_.Clear();
  pending_assocs_.clear();
  pending_parent_assocs_.clear();
  thread_name_priorities_.clear();
  trusted_pids_.clear();
  namespaced_threads_.clear();
  namespaced_processes_.clear();
}

void ProcessTracker::UpdateNamespacedProcess(uint32_t pid,
                                             std::vector<uint32_t> nspid) {
  namespaced_processes_[pid] = {pid, std::move(nspid), {}};
}

void ProcessTracker::UpdateNamespacedThread(uint32_t pid,
                                            uint32_t tid,
                                            std::vector<uint32_t> nstid) {
  PERFETTO_DCHECK(namespaced_processes_.find(pid) !=
                  namespaced_processes_.end());
  auto& process = namespaced_processes_[pid];
  process.threads.emplace(tid);

  namespaced_threads_[tid] = {pid, tid, std::move(nstid)};
}

}  // namespace trace_processor
}  // namespace perfetto