Kernel: Fix pseudo terminal writability

kernel/kernel/OpenFileDescriptorSet.cpp

@@ -360,7 +360,7 @@ namespace Kernel
 		{
 			LockGuard _(inode->m_mutex);
 			if (is_nonblock && !inode->can_read())
-				return 0;
+				return BAN::Error::from_errno(EAGAIN);
 			nread = TRY(inode->read(offset, buffer));
 		}
 
@@ -395,7 +395,7 @@ namespace Kernel
 		{
 			LockGuard _(inode->m_mutex);
 			if (is_nonblock && !inode->can_write())
-				return BAN::Error::from_errno(EWOULDBLOCK);
+				return BAN::Error::from_errno(EAGAIN);
 			nwrite = TRY(inode->write(offset, buffer));
 		}
 

kernel/kernel/Terminal/PseudoTerminal.cpp

@@ -130,6 +130,9 @@ namespace Kernel
 		m_buffer_size -= to_copy;
 		m_buffer_tail = (m_buffer_tail + to_copy) % m_buffer->size();
 
+		if (auto slave = m_slave.lock())
+			slave->m_write_blocker.unblock();
+
 		epoll_notify(EPOLLOUT);
 
 		return to_copy;
@@ -139,12 +142,18 @@ namespace Kernel
 	{
 		auto slave = m_slave.lock();
 		if (!slave)
-			return BAN::Error::from_errno(ENODEV);
+			return BAN::Error::from_errno(EIO);
 		for (size_t i = 0; i < buffer.size(); i++)
 			slave->handle_input_byte(buffer[i]);
 		return buffer.size();
 	}
 
+	void PseudoTerminalMaster::on_close(int)
+	{
+		if (auto slave = m_slave.lock())
+			slave->m_write_blocker.unblock();
+	}
+
 	BAN::ErrorOr<long> PseudoTerminalMaster::ioctl_impl(int request, void* argument)
 	{
 		auto slave = m_slave.lock();
@@ -186,6 +195,15 @@ namespace Kernel
 		return false;
 	}
 
+	bool PseudoTerminalSlave::can_write_impl() const
+	{
+		auto master = m_master.lock();
+		if (!master)
+			return false;
+		SpinLockGuard _(master->m_buffer_lock);
+		return master->m_buffer_size < master->m_buffer->size();
+	}
+
 	BAN::ErrorOr<long> PseudoTerminalSlave::ioctl_impl(int request, void* argument)
 	{
 		switch (request)

kernel/kernel/Terminal/TTY.cpp

@@ -219,7 +219,7 @@ namespace Kernel
 			auto* ptr = reinterpret_cast<const uint8_t*>(ansi_c_str);
 			while (*ptr)
 				handle_input_byte(*ptr++);
-			update_cursor();
+			after_write();
 		}
 	}
 
@@ -297,12 +297,8 @@ namespace Kernel
 
 		if (should_append)
 		{
-			// FIXME: don't ignore these bytes
 			if (m_output.bytes >= m_output.buffer.size())
-			{
-				dwarnln("TTY input full");
 				return;
-			}
 			m_output.buffer[m_output.bytes++] = ch;
 		}
 
@@ -405,6 +401,8 @@ namespace Kernel
 
 		if (m_output.bytes == 0)
 		{
+			if (master_has_closed())
+				return 0;
 			m_output.flush = false;
 			return 0;
 		}
@@ -431,6 +429,13 @@ namespace Kernel
 
 	BAN::ErrorOr<size_t> TTY::write_impl(off_t, BAN::ConstByteSpan buffer)
 	{
+		while (!can_write_impl())
+		{
+			if (master_has_closed())
+				return BAN::Error::from_errno(EIO);
+			TRY(Thread::current().block_or_eintr_indefinite(m_write_blocker, &m_mutex));
+		}
+
 		size_t written = 0;
 
 		{
@@ -438,7 +443,7 @@ namespace Kernel
 			for (; written < buffer.size(); written++)
 				if (!putchar(buffer[written]))
 					break;
-			update_cursor();
+			after_write();
 		}
 
 		if (can_write_impl())
@@ -452,7 +457,7 @@ namespace Kernel
 		ASSERT(s_tty);
 		SpinLockGuard _(s_tty->m_write_lock);
 		s_tty->putchar(ch);
-		s_tty->update_cursor();
+		s_tty->after_write();
 	}
 
 	bool TTY::is_initialized()

kernel/kernel/Terminal/VirtualTTY.cpp

@@ -577,7 +577,7 @@ namespace Kernel
 		return true;
 	}
 
-	void VirtualTTY::update_cursor()
+	void VirtualTTY::after_write()
 	{
 		if (m_cursor_shown != m_last_cursor_shown)
 			m_terminal_driver->set_cursor_shown(m_cursor_shown);