mirrors/ladybird
0
0
Fork 0
mirror of https://github.com/LadybirdBrowser/ladybird.git synced 2025-09-02 15:46:33 +00:00
Code Issues Projects Releases Packages Wiki Activity Actions 10

LibIPC+Meta: Keep message buffer alive until acknowledged by peer

Browse source 
This change ensures that instead of immediately deallocating the message
buffer after sending, we retain it in an acknowledgement wait queue
until an acknowledgement is received from the peer. This is necessary
to handle a behavior of the macOS kernel, which may prematurely
garbage-collect file descriptors contained within the message buffer
before the peer receives them.

The acknowledgement mechanism assumes messages are received in the same
order they were sent so, each acknowledgement message simply indicates
the count of successfully received messages, specifying how many entries
can safely be removed from the acknowledgement wait queue.
This commit is contained in:
Aliaksandr Kalenik 2025-04-05 00:05:20 +02:00 • committed by Andreas Kling
commit c3121c9d8a
Notes: github-actions[bot] 2025-04-05 21:15:26 +00:00
5 changed files with 121 additions and 16 deletions
Download patch file Download diff file Expand all files Collapse all files

29
Libraries/LibIPC/Connection.h
View file

@ -12,6 +12,7 @@
#include <LibCore/EventReceiver.h>
#include <LibIPC/File.h>
#include <LibIPC/Forward.h>
#include <LibIPC/Message.h>
#include <LibIPC/Transport.h>
#include <LibIPC/UnprocessedFileDescriptors.h>
#include <LibThreading/ConditionVariable.h>
@ -26,9 +27,14 @@ class ConnectionBase : public Core::EventReceiver {
public:
virtual ~ConnectionBase() override;
enum class MessageNeedsAcknowledgement {
No,
Yes,
};
[[nodiscard]] bool is_open() const;
ErrorOr<void> post_message(Message const&);
ErrorOr<void> post_message(u32 endpoint_magic, MessageBuffer);
ErrorOr<void> post_message(u32 endpoint_magic, MessageBuffer, MessageNeedsAcknowledgement = MessageNeedsAcknowledgement::Yes);
void shutdown();
virtual void die() { }
@ -36,7 +42,7 @@ public:
Transport& transport() { return m_transport; }
protected:
explicit ConnectionBase(IPC::Stub&, Transport, u32 local_endpoint_magic);
explicit ConnectionBase(IPC::Stub&, Transport, u32 local_endpoint_magic, u32 peer_endpoint_magic);
virtual void may_have_become_unresponsive() { }
virtual void did_become_responsive() { }
@ -62,23 +68,38 @@ protected:
ByteBuffer m_unprocessed_bytes;
u32 m_local_endpoint_magic { 0 };
u32 m_peer_endpoint_magic { 0 };
struct MessageToSend {
MessageBuffer buffer;
MessageNeedsAcknowledgement needs_acknowledgement { MessageNeedsAcknowledgement::Yes };
};
struct SendQueue : public AtomicRefCounted<SendQueue> {
AK::SinglyLinkedList<MessageBuffer> messages;
AK::SinglyLinkedList<MessageToSend> messages;
Threading::Mutex mutex;
Threading::ConditionVariable condition { mutex };
bool running { true };
};
// After a message is sent, it is moved to the acknowledgement wait queue until an acknowledgement is received from the peer.
// This is necessary to handle a specific behavior of the macOS kernel, which may prematurely garbage-collect the file
// descriptor contained in the message before the peer receives it. https://openradar.me/9477351
struct AcknowledgementWaitQueue : public AtomicRefCounted<AcknowledgementWaitQueue> {
AK::SinglyLinkedList<MessageBuffer> messages;
Threading::Mutex mutex;
};
RefPtr<Threading::Thread> m_send_thread;
RefPtr<SendQueue> m_send_queue;
RefPtr<AcknowledgementWaitQueue> m_acknowledgement_wait_queue;
};
template<typename LocalEndpoint, typename PeerEndpoint>
class Connection : public ConnectionBase {
public:
Connection(IPC::Stub& local_stub, Transport transport)
: ConnectionBase(local_stub, move(transport), LocalEndpoint::static_magic())
: ConnectionBase(local_stub, move(transport), LocalEndpoint::static_magic(), PeerEndpoint::static_magic())
{
}