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The deadlock occured with three concurrently running threads: two waiters calling pthread_cond_timedwait() and one signaller calling pthread_cond_signal(). If waiter W1 hits its timeout, the signaller may have called pthread_cond_signal(), detected this waiter and posted the internal 'signal_sem' concurrently. Then, the signaller waits for 'handshake_sem' to ensure the waiter got woken up. Waiter W1 can't consume the 'signal_sem' post by 'sem_wait(&c->signal_sem)' because another waiter W2 may have consumed the post already above in sem_wait/timedwait(). Waiting for a post on 'signal_sem' would block the waiter W1 in perfect deadlock with signaller on 'handshake_sem'. As W1 also owns 'counter_mutex' in this situation, waiter W2 would block when trying to aquire 'counter_mutex' and can't resolve the situation. So, W1 does nothing in this case and we accept the spurious wakeup on next pthread_cond_wait/timedwait(). |
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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.