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c70fed29f7
Previously, the Genode::Timer::curr_time always used the Timer_session::elapsed_ms RPC as back end. Now, Genode::Timer reads this remote time only in a periodic fashion independently from the calls to Genode::Timer::curr_time. If now one calls Genode::Timer::curr_time, the function takes the last read remote time value and adapts it using the timestamp difference since the remote-time read. The conversion factor from timestamps to time is estimated on every remote-time read using the last read remote-time value and the timestamp difference since the last remote time read. This commit also re-works the timeout test. The test now has two stages. In the first stage, it tests fast polling of the Genode::Timer::curr_time. This stage checks the error between locally interpolated and timer-driver time as well as wether the locally interpolated time is monotone and sufficiently homogeneous. In the second stage several periodic and one-shot timeouts are scheduled at once. This stage checks if the timeouts trigger sufficiently precise. This commit adds the new Kernel::time syscall to base-hw. The syscall is solely used by the Genode::Timer on base-hw as substitute for the timestamp. This is because on ARM, the timestamp function uses the ARM performance counter that stops counting when the WFI (wait for interrupt) instruction is active. This instruction, however is used by the base-hw idle contexts that get active when no user thread needs to be scheduled. Thus, the ARM performance counter is not a good choice for time interpolation and we use the kernel internal time instead. With this commit, the timeout library becomes a basic library. That means that it is linked against the LDSO which then provides it to the program it serves. Furthermore, you can't use the timeout library anymore without the LDSO because through the kernel-dependent LDSO make-files we can achieve a kernel-dependent timeout implementation. This commit introduces a structured Duration type that shall successively replace the use of Microseconds, Milliseconds, and integer types for duration values. Open issues: * The timeout test fails on Raspberry PI because of precision errors in the first stage. However, this does not render the framework unusable in general on the RPI but merely is an issue when speaking of microseconds precision. * If we run on ARM with another Kernel than HW the timestamp speed may continuously vary from almost 0 up to CPU speed. The Timer, however, only uses interpolation if the timestamp speed remained stable (12.5% tolerance) for at least 3 observation periods. Currently, one period is 100ms, so its 300ms. As long as this is not the case, Timer_session::elapsed_ms is called instead. Anyway, it might happen that the CPU load was stable for some time so interpolation becomes active and now the timestamp speed drops. In the worst case, we would now have 100ms of slowed down time. The bad thing about it would be, that this also affects the timeout of the period. Thus, it might "freeze" the local time for more than 100ms. On the other hand, if the timestamp speed suddenly raises after some stable time, interpolated time can get too fast. This would shorten the period but nonetheless may result in drifting away into the far future. Now we would have the problem that we can't deliver the real time anymore until it has caught up because the output of Timer::curr_time shall be monotone. So, effectively local time might "freeze" again for more than 100ms. It would be a solution to not use the Trace::timestamp on ARM w/o HW but a function whose return value causes the Timer to never use interpolation because of its stability policy. Fixes #2400
===============================
Genode source-code repositories
===============================
This directory contains the source-code repositories of the Genode OS
Framework. Each sub directory has the same principle layout as described in the
build-system manual:
:Build-system manual:
[https://genode.org/documentation/developer-resources/build_system]
The build system uses a configurable selection of those reposities to obtain
the source codes for the build process. The repositories are not independent
but build upon of each other:
:'base':
This directory contains the source-code repository of the fundamental
frameworks and interfaces of Genode. Furthermore, it contains the generic
parts of core.
:'base-<platform>':
These directories contain platform-specific source-code repositories
complementing the 'base' repository. The following platforms are supported:
:'linux':
Linux kernel (both x86_32 and x86_64)
:'nova':
NOVA hypervisor developed at University of Technology Dresden
See [https://genode.org/documentation/platforms/nova]
:'foc':
Fiasco.OC is a modernized version of the Fiasco microkernel with a
completely revised kernel interface fostering capability-based
security. It is not compatible with L4/Fiasco.
See [https://genode.org/documentation/platforms/foc]
:'hw':
The hw platform allows the execution of Genode on bare ARM and x86 hardware
without the need for a separate kernel. The kernel functionality is
included in core except in the special case of the Muen separation
kernel.
See [https://genode.org/documentation/platforms/hw] and
[https://genode.org/documentation/platforms/muen]
:'okl4':
OKL4 kernel (x86_32 and ARM) developed at Open-Kernel-Labs.
See [https://genode.org/documentation/platforms/okl4]
:'pistachio':
L4ka::Pistachio kernel developed at University of Karlsruhe.
See [https://genode.org/documentation/platforms/pistachio]
:'fiasco':
L4/Fiasco kernel developed at University of Technology Dresden.
See [https://genode.org/documentation/platforms/fiasco]
:'sel4':
seL4 microkernel developed at NICTA/General Dynamics
See[https://sel4.systems/]
:'os':
This directory contains the non-base OS components such as the init process,
device drivers, and basic system services.
:'demo':
This directory contains the source-code repository of various services and
applications that we use for demonstration purposes. For example, a graphical
application launcher called Launchpad and the Scout tutorial browser.
:'hello_tutorial':
Tutorial for creating a simple client-server scenario with Genode. This
repository includes documentation and the complete source code.
:'libports':
This source-code repository contains ports of popular open-source libraries
to Genode, most importantly the C library. The repository contains no
upstream source code but means to download the code and adapt it to Genode.
For instructions about how to use this mechanism, please consult the README
file at the top level of the repository. Among the 3rd-party libraries
are Qt5, libSDL, freetype, Python, ncurses, Mesa, and libav.
:'dde_linux':
This source-code repository contains the device driver environment for
executing Linux device drivers natively on Genode. Currently, this
repository hosts the USB stack.
:'dde_ipxe':
This source-code repository contains the device-driver environment for
executing drivers of the iPXE project.
:'dde_bsd':
This source-code repository contains the device-driver environment for
drivers of the OpenBSD operating system.
:'dde_rump':
This source-code repository contains the port of rump kernels, which are
used to execute subsystems of the NetBSD kernel as user level processes.
The repository contains a server that uses a rump kernel to provide
various NetBSD file systems to Genode.
:'ports':
This source-code repository hosts ports of 3rd-party applications to
Genode. The repository does not contain upstream source code but provides
a mechanism for downloading the official source distributions and adapt
them to the Genode environment. The used mechanism is roughly the same
as used for the 'libports' repository. Please consult 'libports/README'
for further information.
:'gems':
This source-code repository contains Genode applications that use
both native Genode interfaces as well as features of other high-level
repositories, in particular shared libraries provided by 'libports'.