Emery Hemingway
7e08bba25c
When the cached_fs_rom saturates the packet stream of its File_system session it will call the session request handler recursively as pending transfers are completed. This is bad because the content of the XML node currently being processed will change. The session request handler can no longer be called directly, but the "schedule" method will submit a signal to the request handler, and requests will be processed after the current operation has completed.
138 lines
3.6 KiB
C++
138 lines
3.6 KiB
C++
/*
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* \brief Utilities for handling the 'session_requests' ROM
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* \author Emery Hemingway
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* \date 2018-04-08
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*/
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/*
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* Copyright (C) 2018 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 Affero General Public License version 3.
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*/
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#ifndef __SESSION_REQUESTS_H_
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#define __SESSION_REQUESTS_H_
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#include <base/attached_rom_dataspace.h>
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#include <base/session_state.h>
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#include <base/component.h>
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namespace Genode {
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struct Session_request_handler;
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class Session_requests_rom;
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};
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struct Genode::Session_request_handler : Interface
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{
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virtual void handle_session_create(Session_state::Name const &,
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Parent::Server::Id,
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Session_state::Args const &) = 0;
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virtual void handle_session_upgrade(Parent::Server::Id,
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Session_state::Args const &) { }
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virtual void handle_session_close(Parent::Server::Id) = 0;
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};
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class Genode::Session_requests_rom : public Signal_handler<Session_requests_rom>
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{
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private:
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Parent &_parent;
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Session_request_handler &_requests_handler;
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Attached_rom_dataspace _parent_rom;
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void _process()
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{
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_parent_rom.update();
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Xml_node requests = _parent_rom.xml();
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auto const create_fn = [&] (Xml_node request)
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{
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Parent::Server::Id const id {
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request.attribute_value("id", ~0UL) };
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typedef Session_state::Name Name;
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typedef Session_state::Args Args;
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Name name { };
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Args args { };
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try {
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name = request.attribute_value("service", Name());
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args = request.sub_node("args").decoded_content<Args>();
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} catch (...) {
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Genode::error("failed to parse request ", request);
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return;
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}
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try { _requests_handler.handle_session_create(name, id, args); }
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catch (Service_denied) {
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_parent.session_response(id, Parent::SERVICE_DENIED); }
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catch (Insufficient_ram_quota) {
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_parent.session_response(id, Parent::INSUFFICIENT_RAM_QUOTA); }
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catch (Insufficient_cap_quota) {
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_parent.session_response(id, Parent::INSUFFICIENT_CAP_QUOTA); }
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catch (...) {
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error("unhandled exception while creating session");
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_parent.session_response(id, Parent::SERVICE_DENIED);
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throw;
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}
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};
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auto const upgrade_fn = [&] (Xml_node request)
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{
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Parent::Server::Id const id {
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request.attribute_value("id", ~0UL) };
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typedef Session_state::Args Args;
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Args args { };
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try { args = request.sub_node("args").decoded_content<Args>(); }
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catch (...) {
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Genode::error("failed to parse request ", request);
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return;
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}
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_requests_handler.handle_session_upgrade(id, args);
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};
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auto const close_fn = [&] (Xml_node request)
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{
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Parent::Server::Id const id {
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request.attribute_value("id", ~0UL) };
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_requests_handler.handle_session_close(id);
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};
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/* close sessions to free resources */
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requests.for_each_sub_node("close", close_fn);
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/* service existing sessions */
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requests.for_each_sub_node("upgrade", upgrade_fn);
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/* create new sessions */
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requests.for_each_sub_node("create", create_fn);
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}
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public:
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Session_requests_rom(Genode::Env &env,
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Session_request_handler &requests_handler)
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: Signal_handler<Session_requests_rom>(env.ep(), *this, &Session_requests_rom::_process),
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_parent(env.parent()),
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_requests_handler(requests_handler),
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_parent_rom(env, "session_requests")
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{
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_parent_rom.sigh(*this);
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}
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/**
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* Post a signal to this requests handler
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*/
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void schedule() {
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Signal_transmitter(*this).submit(); }
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};
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#endif
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