78 lines
2.1 KiB
C++
78 lines
2.1 KiB
C++
/*
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* \brief Environment initialization
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* \author Norman Feske
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* \author Christian Helmuth
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* \date 2006-07-27
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*/
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/*
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* Copyright (C) 2006-2013 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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#include <platform_env.h>
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namespace Genode {
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/*
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* Request pointer to static environment of the Genode application
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*/
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Env *env()
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{
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/*
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* By placing the environment as static object here, we ensure that its
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* constructor gets called when this function is used the first time.
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*/
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static Genode::Platform_env _env;
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return &_env;
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}
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}
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static Genode::Signal_receiver *resource_sig_rec()
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{
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static Genode::Signal_receiver sig_rec;
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return &sig_rec;
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}
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Genode::Signal_context_capability
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Genode::Expanding_parent_client::_fallback_sig_cap()
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{
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static Signal_context _sig_ctx;
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static Signal_context_capability _sig_cap;
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/* create signal-context capability only once */
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if (!_sig_cap.valid()) {
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/*
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* Because the 'manage' function consumes meta data of the signal
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* session, calling it may result in an 'Out_of_metadata' error. The
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* 'manage' function handles this error by upgrading the session quota
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* accordingly. However, this upgrade, in turn, may result in the
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* depletion of the process' RAM quota. In this case, the process would
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* issue a resource request to the parent. But in order to do so, the
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* fallback signal handler has to be constructed. To solve this
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* hen-and-egg problem, we allocate a so-called emergency RAM reserve
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* immediately at the startup of the process as part of the
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* 'Platform_env'. When initializing the fallback signal handler, these
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* resources get released in order to ensure an eventual upgrade of the
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* signal session to succeed.
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*
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* The corner case is tested by 'os/src/test/resource_request'.
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*/
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_emergency_ram_reserve.release();
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_sig_cap = resource_sig_rec()->manage(&_sig_ctx);
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}
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return _sig_cap;
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}
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void Genode::Expanding_parent_client::_wait_for_resource_response()
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{
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resource_sig_rec()->wait_for_signal();
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}
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