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px4_daemon: fix locking

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It was not enough to lock individual accesses to the maps.
For example it could happen that a thread was started and exited very
quickly, before the pthread_t item was inserted into the map, such
that when the cleanup method was called, the thread and pipe fd were not
found (and fd=0=stdin was closed).
This commit is contained in:
Beat Küng
2018-08-06 08:08:40 +02:00
committed by Lorenz Meier
parent 5b171bd614
commit 1f0655302c
3 changed files with 68 additions and 122 deletions
Download Patch File Download Diff File Expand all files Collapse all files
platforms/posix/src/px4_daemon/server.cpp
+48 -15
View File
@@ -58,7 +58,8 @@ namespace px4_daemon
Server *Server::_instance = nullptr;
Server::Server(int instance_id)
: _instance_id(instance_id)
: _mutex(PTHREAD_MUTEX_INITIALIZER),
_instance_id(instance_id)
{
_instance = this;
}
@@ -194,36 +195,53 @@ Server::_execute_cmd_packet(const client_send_packet_s &packet)
args->pipe_fd = pipe_fd;
args->is_atty = packet.payload.execute_msg.is_atty;
if (0 != pthread_create(&new_pthread, NULL, Server::_run_cmd, (void *)args)) {
PX4_ERR("could not start pthread");
_lock(); // need to lock, otherwise the thread could already exit before we insert into the map
ret = pthread_create(&new_pthread, NULL, Server::_run_cmd, (void *)args);
if (ret != 0) {
PX4_ERR("could not start pthread (%i)", ret);
delete args;
return;
} else {
// We won't join the thread, so detach to automatically release resources at its end
pthread_detach(new_pthread);
// We keep two maps for cleanup if a thread is finished or killed.
_client_uuid_to_pthread.insert(std::pair<uint64_t, pthread_t>
(packet.header.client_uuid, new_pthread));
_pthread_to_pipe_fd.insert(std::pair<pthread_t, int>
(new_pthread, pipe_fd));
}
// We keep two maps for cleanup if a thread is finished or killed.
_client_uuid_to_pthread.insert(std::pair<uint64_t, pthread_t>
(packet.header.client_uuid, new_pthread));
_pthread_to_pipe_fd.insert(std::pair<pthread_t, int>
(new_pthread, pipe_fd));
_unlock();
}
void
Server::_kill_cmd_packet(const client_send_packet_s &packet)
{
// TODO: we currently ignore the signal type.
_lock();
pthread_t pthread_to_kill = _client_uuid_to_pthread.get(packet.header.client_uuid);
// TODO: we currently ignore the signal type.
auto client_uuid_iter = _client_uuid_to_pthread.find(packet.header.client_uuid);
if (client_uuid_iter == _client_uuid_to_pthread.end()) {
_unlock();
return;
}
pthread_t pthread_to_kill = client_uuid_iter->second;
// TODO: use a more graceful exit method to avoid resource leaks
int ret = pthread_cancel(pthread_to_kill);
__cleanup_thread(packet.header.client_uuid);
_unlock();
if (ret != 0) {
PX4_ERR("failed to cancel thread");
}
_cleanup_thread(packet.header.client_uuid);
// We don't send retval when we get killed.
// The client knows this and just exits without confirmation.
}
@@ -291,9 +309,24 @@ Server::_send_retval(const int pipe_fd, const int retval, const uint64_t client_
void
Server::_cleanup_thread(const uint64_t client_uuid)
{
pthread_t pthread_killed = _client_uuid_to_pthread.get(client_uuid);
int pipe_fd = _pthread_to_pipe_fd.get(pthread_killed);
_lock();
__cleanup_thread(client_uuid);
_unlock();
}
void
Server::__cleanup_thread(const uint64_t client_uuid)
{
pthread_t pthread_killed = _client_uuid_to_pthread[client_uuid];
auto pipe_iter = _pthread_to_pipe_fd.find(pthread_killed);
if (pipe_iter == _pthread_to_pipe_fd.end()) {
// can happen if the thread already exited and then got a kill packet
PX4_DEBUG("pipe fd already closed");
return;
}
int pipe_fd = pipe_iter->second;
close(pipe_fd);
char path[RECV_PIPE_PATH_LEN] = {};