Adding upstream version 18.2.2.upstream/18.2.2

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 21 insertions, 0 deletions

diff --git a/src/boost/libs/context/README.md b/src/boost/libs/context/README.md
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+boost.context
+=============
+
+boost.context is a foundational library that provides a sort of cooperative multitasking on a single thread.
+By providing an abstraction of the current execution state in the current thread, including the stack (with 
+local variables) and stack pointer, all registers and CPU flags, and the instruction pointer, a execution_context 
+instance represents a specific point in the application's execution path. This is useful for building 
+higher-level abstractions, like coroutines, cooperative threads (userland threads) or an equivalent to 
+C# keyword yield in C++.
+
+A fiber provides the means to suspend the current execution path and to transfer execution control, 
+thereby permitting another fiber to run on the current thread. This state full transfer mechanism 
+enables a fiber to suspend execution from within nested functions and, later, to resume from where it 
+was suspended. While the execution path represented by a fiber only runs on a single thread, it can be 
+migrated to another thread at any given time.
+
+A context switch between threads requires system calls (involving the OS kernel), which can cost more than 
+thousand CPU cycles on x86 CPUs. By contrast, transferring control among fibers requires only fewer than 
+hundred CPU cycles because it does not involve system calls as it is done within a single thread.
+
+boost.context requires C++11!