58 lines
1.4 KiB
C++
58 lines
1.4 KiB
C++
#include <mutex>
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#include <stdexcept>
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#include <climits>
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class hierarchical_mutex
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{
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std::mutex internal_mutex;
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unsigned long const hierarchy_value;
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unsigned long previous_hierarchy_value;
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static thread_local unsigned long this_thread_hierarchy_value;
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void check_for_hierarchy_violation()
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{
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if(this_thread_hierarchy_value <= hierarchy_value)
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{
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throw std::logic_error("mutex hierarchy violated");
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}
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}
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void update_hierarchy_value()
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{
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previous_hierarchy_value=this_thread_hierarchy_value;
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this_thread_hierarchy_value=hierarchy_value;
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}
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public:
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explicit hierarchical_mutex(unsigned long value):
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hierarchy_value(value),
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previous_hierarchy_value(0)
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{}
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void lock()
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{
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check_for_hierarchy_violation();
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internal_mutex.lock();
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update_hierarchy_value();
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}
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void unlock()
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{
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this_thread_hierarchy_value=previous_hierarchy_value;
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internal_mutex.unlock();
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}
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bool try_lock()
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{
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check_for_hierarchy_violation();
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if(!internal_mutex.try_lock())
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return false;
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update_hierarchy_value();
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return true;
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}
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};
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thread_local unsigned long
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hierarchical_mutex::this_thread_hierarchy_value(ULONG_MAX);
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int main()
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{
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hierarchical_mutex m1(42);
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hierarchical_mutex m2(2000);
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}
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