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LibCore: Have IPC server connections queue up unsendable messages

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If an IPC client is giving us EAGAIN when trying to send him a message,
we now queue up the messages inside the CoreIPCServer::Connection and
will retry flushing them on next post/receive.

This prevents WindowServer from freezing up when one of its clients is
not taking care of its incoming messages.
This commit is contained in:
Andreas Kling 2019-11-03 12:36:35 +01:00
parent 8c45891c80
commit 31c1b8ec3e
Notes: sideshowbarker 2024-07-19 11:27:18 +09:00 
Author: https://github.com/awesomekling
Commit: https://github.com/SerenityOS/serenity/commit/31c1b8ec3ef
1 changed files with 46 additions and 21 deletions
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67
Libraries/LibCore/CoreIPCServer.h
View file

@ -1,5 +1,6 @@
#pragma once
#include <AK/Queue.h>
#include <LibCore/CEvent.h>
#include <LibCore/CEventLoop.h>
#include <LibCore/CIODevice.h>
@ -70,7 +71,10 @@ namespace Server {
, m_client_id(client_id)
{
add_child(socket);
m_socket->on_ready_to_read = [this] { drain_client(); };
m_socket->on_ready_to_read = [this] {
drain_client();
flush_outgoing_messages();
};
#if defined(CIPC_DEBUG)
dbg() << "S: Created new Connection " << fd << client_id << " and said hello";
#endif
@ -89,9 +93,16 @@ namespace Server {
#if defined(CIPC_DEBUG)
dbg() << "S: -> C " << int(message.type) << " extra " << extra_data.size();
#endif
if (try_send_message(message, extra_data))
return;
QueuedMessage queued_message { message, extra_data };
if (!extra_data.is_empty())
const_cast<ServerMessage&>(message).extra_size = extra_data.size();
queued_message.message.extra_size = extra_data.size();
m_queue.enqueue(move(queued_message));
}
bool try_send_message(const ServerMessage& message, const ByteBuffer& extra_data)
{
struct iovec iov[2];
int iov_count = 1;
@ -104,29 +115,36 @@ namespace Server {
++iov_count;
}
int nwritten = 0;
for (;;) {
nwritten = writev(m_socket->fd(), iov, iov_count);
if (nwritten < 0) {
switch (errno) {
case EPIPE:
dbgprintf("Connection::post_message: Disconnected from peer.\n");
shutdown();
return;
case EAGAIN:
// FIXME: It would be better to push these onto a queue so we can go back
// to servicing other clients.
sched_yield();
continue;
default:
perror("Connection::post_message writev");
ASSERT_NOT_REACHED();
}
int nwritten = writev(m_socket->fd(), iov, iov_count);
if (nwritten < 0) {
switch (errno) {
case EPIPE:
dbgprintf("Connection::post_message: Disconnected from peer.\n");
shutdown();
return false;
case EAGAIN:
#ifdef CIPC_DEBUG
dbg() << "EAGAIN when trying to send WindowServer message, queue size: " << m_queue.size();
#endif
return false;
default:
perror("Connection::post_message writev");
ASSERT_NOT_REACHED();
}
break;
}
ASSERT(nwritten == (int)(sizeof(message) + extra_data.size()));
return true;
}
void flush_outgoing_messages()
{
while (!m_queue.is_empty()) {
auto& queued_message = m_queue.head();
if (!try_send_message(queued_message.message, queued_message.extra_data))
break;
m_queue.dequeue();
}
}
void drain_client()
@ -209,6 +227,13 @@ namespace Server {
private:
RefPtr<CLocalSocket> m_socket;
struct QueuedMessage {
ServerMessage message;
ByteBuffer extra_data;
};
Queue<QueuedMessage, 16> m_queue;
int m_client_id { -1 };
int m_client_pid { -1 };
};