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LibIPC+LibWeb: Add an IPC helper to transfer an IPC message buffer

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This large block of code is repeated nearly verbatim in LibWeb. Move it
to a helper function that both LibIPC and LibWeb can defer to. This will
let us make changes to this method in a singular location going forward.

Note this is a bit of a regression for the MessagePort. It now suffers
from the same performance issue that IPC messages face - we prepend the
meessage size to the message buffer. This degredation is very temporary
though, as a fix is imminent, and this change makes that fix easier.
This commit is contained in:
Timothy Flynn 2024-01-02 20:14:18 -05:00 • committed by Andreas Kling
parent bf15b66117
commit 91558fa381
6 changed files with 72 additions and 91 deletions
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47
Userland/Libraries/LibWeb/HTML/MessagePort.cpp
View file

@ -253,54 +253,9 @@ ErrorOr<void> MessagePort::send_message_on_socket(SerializedTransferRecord const
{
IPC::MessageBuffer buffer;
IPC::Encoder encoder(buffer);
MUST(encoder.encode<u32>(0)); // placeholder for total size
MUST(encoder.encode(serialize_with_transfer_result));
u32 buffer_size = buffer.data.size() - sizeof(u32); // size of *payload*
buffer.data[0] = buffer_size & 0xFF;
buffer.data[1] = (buffer_size >> 8) & 0xFF;
buffer.data[2] = (buffer_size >> 16) & 0xFF;
buffer.data[3] = (buffer_size >> 24) & 0xFF;
for (auto& fd : buffer.fds) {
if (auto result = m_fd_passing_socket->send_fd(fd->value()); result.is_error()) {
return Error::from_string_view("Can't send fd"sv);
}
}
ReadonlyBytes bytes_to_write { buffer.data.span() };
int writes_done = 0;
size_t initial_size = bytes_to_write.size();
while (!bytes_to_write.is_empty()) {
auto maybe_nwritten = m_socket->write_some(bytes_to_write);
writes_done++;
if (maybe_nwritten.is_error()) {
auto error = maybe_nwritten.release_error();
if (error.is_errno()) {
// FIXME: This is a hacky way to at least not crash on large messages
// The limit of 100 writes is arbitrary, and there to prevent indefinite spinning on the EventLoop
if (error.code() == EAGAIN && writes_done < 100) {
sched_yield();
continue;
}
switch (error.code()) {
case EPIPE:
return Error::from_string_literal("IPC::Connection::post_message: Disconnected from peer");
case EAGAIN:
return Error::from_string_literal("IPC::Connection::post_message: Peer buffer overflowed");
default:
return Error::from_syscall("IPC::Connection::post_message write"sv, -error.code());
}
} else {
return error;
}
}
bytes_to_write = bytes_to_write.slice(maybe_nwritten.value());
}
if (writes_done > 1) {
dbgln("LibIPC::Connection FIXME Warning, needed {} writes needed to send message of size {}B, this is pretty bad, as it spins on the EventLoop", writes_done, initial_size);
}
TRY(buffer.transfer_message(*m_fd_passing_socket, *m_socket));
return {};
}