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Until now, block drivers had to deal with a pointer to the client session component, e.g.: to acknowledge block packets already processed. When a session was closed, the driver object wasn't informed explicitly, which leads to defensive programming, or lastly to a race-condition in test-blk-srv. To prevent from this class of errors, the pointer is now private to the generic block driver base class, and not accessible to the concrete driver implementation. Moreover, the driver gets explicitly informed when a session got invalidated. Ref #113
308 lines
8.5 KiB
C++
308 lines
8.5 KiB
C++
/*
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* \brief Block-session component
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* \author Christian Helmuth
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* \author Stefan Kalkowski
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* \date 2011-05-20
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*/
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/*
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* Copyright (C) 2011-2013 Genode Labs GmbH
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*
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* This file is part of the Genode OS framework, which is distributed
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* under the terms of the GNU General Public License version 2.
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*/
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#ifndef _INCLUDE__BLOCK__COMPONENT_H_
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#define _INCLUDE__BLOCK__COMPONENT_H_
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#include <root/component.h>
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#include <os/signal_rpc_dispatcher.h>
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#include <os/server.h>
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#include <block/driver.h>
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namespace Block {
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using namespace Genode;
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class Session_component_base;
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class Session_component;
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class Root;
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};
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/**
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* We have a hen and egg situation that makes this base class necessary.
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* The Block::Session_rpc_object construction depends on a dataspace for
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* the packet stream. The dataspace on the other hand is constructed by
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* the driver, which is created on demand when creating a session.
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* When creating the driver, and dataspace outside the Session_component
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* constructor within _create_session of the root component, we would have
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* to destroy the driver and dataspace within the destructor body of
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* Session_component, which will lead to problems, because the packet stream
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* destructors will be called after the shared memory already vanished.
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*/
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class Block::Session_component_base
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{
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protected:
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Driver_factory &_driver_factory;
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Driver &_driver;
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Ram_dataspace_capability _rq_ds;
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Session_component_base(Driver_factory &factory, size_t tx_buf_size)
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: _driver_factory(factory),
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_driver(*factory.create()),
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_rq_ds(_driver.alloc_dma_buffer(tx_buf_size)) {}
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~Session_component_base()
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{
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_driver.free_dma_buffer(_rq_ds);
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_driver_factory.destroy(&_driver);
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}
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};
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class Block::Session_component : public Block::Session_component_base,
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public Block::Driver_session
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{
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private:
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addr_t _rq_phys;
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Signal_rpc_member<Session_component> _sink_ack;
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Signal_rpc_member<Session_component> _sink_submit;
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bool _req_queue_full;
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bool _ack_queue_full;
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Packet_descriptor _p_to_handle;
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unsigned _p_in_fly;
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/**
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* Acknowledge a packet already handled
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*/
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inline void _ack_packet(Packet_descriptor &packet)
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{
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if (!tx_sink()->ready_to_ack())
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PERR("Not ready to ack!");
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tx_sink()->acknowledge_packet(packet);
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_p_in_fly--;
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}
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/**
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* Range check packet request
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*/
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inline bool _range_check(Packet_descriptor &p) {
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return p.block_number() + p.block_count() - 1
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< _driver.block_count(); }
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/**
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* Handle a single request
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*/
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void _handle_packet(Packet_descriptor packet)
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{
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_p_to_handle = packet;
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_p_to_handle.succeeded(false);
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/* ignore invalid packets */
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if (!packet.valid() || !_range_check(_p_to_handle)) {
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_ack_packet(_p_to_handle);
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return;
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}
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try {
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switch (_p_to_handle.operation()) {
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case Block::Packet_descriptor::READ:
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if (_driver.dma_enabled())
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_driver.read_dma(packet.block_number(),
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packet.block_count(),
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_rq_phys + packet.offset(),
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_p_to_handle);
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else
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_driver.read(packet.block_number(),
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packet.block_count(),
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tx_sink()->packet_content(packet),
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_p_to_handle);
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break;
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case Block::Packet_descriptor::WRITE:
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if (_driver.dma_enabled())
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_driver.write_dma(packet.block_number(),
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packet.block_count(),
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_rq_phys + packet.offset(),
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_p_to_handle);
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else
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_driver.write(packet.block_number(),
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packet.block_count(),
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tx_sink()->packet_content(packet),
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_p_to_handle);
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break;
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default:
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throw Driver::Io_error();
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}
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} catch (Driver::Request_congestion) {
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_req_queue_full = true;
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} catch (Driver::Io_error) {
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_ack_packet(_p_to_handle);
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}
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}
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/**
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* Triggered when a packet was placed into the empty submit queue
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*/
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void _packet_avail(unsigned)
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{
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/*
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* as long as more packets are available, and we're able to ack
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* them, and the driver's request queue isn't full,
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* direct the packet request to the driver backend
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*/
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for (_ack_queue_full = (_p_in_fly >= tx_sink()->ack_slots_free());
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!_req_queue_full && !_ack_queue_full
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&& tx_sink()->packet_avail();
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_ack_queue_full = (++_p_in_fly >= tx_sink()->ack_slots_free()))
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_handle_packet(tx_sink()->get_packet());
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}
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/**
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* Triggered when an ack got removed from the full ack queue
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*/
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void _ready_to_ack(unsigned) { _packet_avail(0); }
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public:
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/**
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* Constructor
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*
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* \param rq_ds shared dataspace for packet stream
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* \param driver block driver backend
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* \param driver_factory factory to create and destroy driver objects
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* \param ep entrypoint handling this session component
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*/
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Session_component(Driver_factory &driver_factory,
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Server::Entrypoint &ep, size_t buf_size)
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: Session_component_base(driver_factory, buf_size),
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Driver_session(_rq_ds, ep.rpc_ep()),
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_rq_phys(Dataspace_client(_rq_ds).phys_addr()),
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_sink_ack(ep, *this, &Session_component::_ready_to_ack),
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_sink_submit(ep, *this, &Session_component::_packet_avail),
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_req_queue_full(false),
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_p_in_fly(0)
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{
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_tx.sigh_ready_to_ack(_sink_ack);
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_tx.sigh_packet_avail(_sink_submit);
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_driver.session(this);
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}
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~Session_component() { _driver.session(nullptr); }
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/**
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* Acknowledges a packet processed by the driver to the client
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*
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* \param packet the packet to acknowledge
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* \param success indicated whether the processing was successful
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*
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* \throw Ack_congestion
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*/
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void ack_packet(Packet_descriptor &packet, bool success)
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{
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packet.succeeded(success);
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_ack_packet(packet);
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if (!_req_queue_full && !_ack_queue_full)
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return;
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/*
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* when the driver's request queue was full,
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* handle last unprocessed packet taken out of submit queue
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*/
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if (_req_queue_full) {
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_req_queue_full = false;
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_handle_packet(_p_to_handle);
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}
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/* resume packet processing */
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_packet_avail(0);
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}
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/*******************************
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** Block session interface **
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*******************************/
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void info(sector_t *blk_count, size_t *blk_size,
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Operations *ops)
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{
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*blk_count = _driver.block_count();
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*blk_size = _driver.block_size();
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*ops = _driver.ops();
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}
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void sync() { _driver.sync(); }
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};
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/**
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* Root component, handling new session requests
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*/
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class Block::Root : public Genode::Root_component<Block::Session_component,
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Single_client>
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{
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private:
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Driver_factory &_driver_factory;
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Server::Entrypoint &_ep;
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protected:
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/**
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* Always returns the singleton block-session component
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*/
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Session_component *_create_session(const char *args)
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{
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size_t ram_quota =
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Arg_string::find_arg(args, "ram_quota" ).ulong_value(0);
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size_t tx_buf_size =
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Arg_string::find_arg(args, "tx_buf_size").ulong_value(0);
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/* delete ram quota by the memory needed for the session */
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size_t session_size = max((size_t)4096,
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sizeof(Session_component)
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+ sizeof(Allocator_avl));
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if (ram_quota < session_size)
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throw Root::Quota_exceeded();
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/*
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* Check if donated ram quota suffices for both
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* communication buffers. Also check both sizes separately
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* to handle a possible overflow of the sum of both sizes.
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*/
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if (tx_buf_size > ram_quota - session_size) {
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PERR("insufficient 'ram_quota', got %zd, need %zd",
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ram_quota, tx_buf_size + session_size);
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throw Root::Quota_exceeded();
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}
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return new (md_alloc()) Session_component(_driver_factory,
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_ep, tx_buf_size);
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}
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public:
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/**
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* Constructor
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*
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* \param ep entrypoint handling this root component
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* \param md_alloc allocator to allocate session components
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* \param driver_factory factory to create and destroy driver backend
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* \param receiver signal receiver managing signals of the client
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*/
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Root(Server::Entrypoint &ep, Allocator *md_alloc,
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Driver_factory &driver_factory)
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: Root_component(&ep.rpc_ep(), md_alloc),
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_driver_factory(driver_factory), _ep(ep) { }
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};
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#endif /* _INCLUDE__BLOCK__COMPONENT_H_ */
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