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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
This directory contains ports of popular 3rd-party software to Genode. Usage ----- The tool './tool/ports/prepare_port' in the toplevel directory automates the task of downloading and preparing the library source codes. You can select individual packages that have to be prepared by specifying their base names (without the version number) as command-line argument. For example, the following command prepares both the C library and the Freetype library: ! ./tool/ports/prepare_port libc freetype To compile and link against 3rd-party libraries of the 'libports' repository, you have to include the repository into the build process by appending it to the 'REPOSITORIES' declaration of your '<build-dir>/etc/build.conf' file. Under the hood -------------- For each library, there is a file contained in the 'libports/ports/' subdirectory. The file is named after the library and contains the library-specific rules for downloading the source code and installing header files. How does 'libports' relate to the other repositories? ----------------------------------------------------- Most libraries hosted in the 'libports' repository expect a complete C library, which is provided with the 'libc' package. Please do not forget to prepare the libc package when using any of the other libports packages. The libc, in turn, depends on the 'os' repository for its back end. Because the 'os' repository is the home of the dynamic linker, libraries contained in 'libports' are safe to assume the presence of the dynamic linker and, thus, should be built as shared libraries.