PowerUser/mutex-cpp
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mutex: comments and name clarity

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PowerUser64 2024-11-19 15:28:19 -08:00
parent dc89fc4ce2
commit d9089c4348
1 changed files with 11 additions and 11 deletions
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22
main.cpp
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@ -18,10 +18,10 @@ typedef void *(*ThreadTask)(const struct thread_data &);
typedef void *(*PthreadFun)(void *arg); typedef void *(*PthreadFun)(void *arg);
struct thread_group { struct thread_group {
bool wants_mutex[NUM_THREADS] = {0}; bool wants_mutex[NUM_THREADS] = {0}; // set by the thread
bool has_mutex[NUM_THREADS] = {0}; bool has_mutex[NUM_THREADS] = {0}; // set by us, read by thread
bool manager_took_mutex[NUM_THREADS] = {0}; bool can_ask_for_mutex[NUM_THREADS] = {1}; // set by us, read by thread
bool threads_finished[NUM_THREADS] = {0}; bool threads_finished[NUM_THREADS] = {0}; // set by thread
ThreadTask task; ThreadTask task;
size_t total_threads; size_t total_threads;
void *data; void *data;
@ -31,7 +31,7 @@ struct thread_data {
size_t id; size_t id;
bool *wants_mutex; bool *wants_mutex;
const bool *has_mutex; const bool *has_mutex;
const bool *manager_took_mutex; const bool *can_ask_for_mutex;
bool *is_finished; bool *is_finished;
void *data; void *data;
}; };
@ -56,7 +56,7 @@ void *thread_task_increment(const struct thread_data &thread) {
{ {
// wait for permission to ask for the mutex // wait for permission to ask for the mutex
while (!*thread.manager_took_mutex) while (!*thread.can_ask_for_mutex)
; ;
// say we want the mutex // say we want the mutex
(*thread.wants_mutex) = true; (*thread.wants_mutex) = true;
@ -105,8 +105,8 @@ void do_threading(struct thread_group threads) {
threads.total_threads * sizeof(*threads.threads_finished)); threads.total_threads * sizeof(*threads.threads_finished));
// at the start, we have the mutex and haven't given it // at the start, we have the mutex and haven't given it
memset(threads.manager_took_mutex, 1, memset(threads.can_ask_for_mutex, 1,
threads.total_threads * sizeof(*threads.manager_took_mutex)); threads.total_threads * sizeof(*threads.can_ask_for_mutex));
// create thread data // create thread data
for (size_t tid = 0; tid < threads.total_threads; ++tid) { for (size_t tid = 0; tid < threads.total_threads; ++tid) {
@ -114,7 +114,7 @@ void do_threading(struct thread_group threads) {
.id = tid, .id = tid,
.wants_mutex = &threads.wants_mutex[tid], .wants_mutex = &threads.wants_mutex[tid],
.has_mutex = &threads.has_mutex[tid], .has_mutex = &threads.has_mutex[tid],
.manager_took_mutex = &threads.manager_took_mutex[tid], .can_ask_for_mutex = &threads.can_ask_for_mutex[tid],
.is_finished = &threads.threads_finished[tid], .is_finished = &threads.threads_finished[tid],
.data = threads.data, .data = threads.data,
}; };
@ -154,9 +154,9 @@ void do_threading(struct thread_group threads) {
// take the mutex from the thread that has it // take the mutex from the thread that has it
threads.has_mutex[tid_has] = false; threads.has_mutex[tid_has] = false;
threads.manager_took_mutex[tid_has] = true; threads.can_ask_for_mutex[tid_has] = true;
// give the mutex to the thread that wants it // give the mutex to the thread that wants it
threads.manager_took_mutex[tid_wants] = false; threads.can_ask_for_mutex[tid_wants] = false;
threads.has_mutex[tid_wants] = true; threads.has_mutex[tid_wants] = true;
} }