os_threading.h

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// Copyright 2019-2022, Collabora, Ltd.
// SPDX-License-Identifier: BSL-1.0
/*!
 * @file
 * @brief  Wrapper around OS threading native functions.
 * @author Jakob Bornecrantz <jakob@collabora.com>
 *
 * @ingroup aux_os
 */
 
#pragma once
 
#include "xrt/xrt_compiler.h"
#include "xrt/xrt_config_os.h"
 
#include "util/u_misc.h"
 
#include "os/os_time.h"
 
#if defined(XRT_OS_LINUX) || defined(XRT_ENV_MINGW)
#include <pthread.h>
#include <semaphore.h>
#include <assert.h>
#define OS_THREAD_HAVE_SETNAME
#elif defined(XRT_OS_WINDOWS)
#include <pthread.h>
#include <sched.h>
#include <semaphore.h>
#include <assert.h>
#define OS_THREAD_HAVE_SETNAME
#else
#error "OS not supported"
#endif
 
#ifdef __cplusplus
extern "C" {
#endif
 
 
/*!
 * @addtogroup aux_os
 * @{
 */
 
/*
 *
 * Mutex
 *
 */
 
/*!
 * A wrapper around a native mutex.
 */
struct os_mutex
{
        pthread_mutex_t mutex;
 
#ifndef NDEBUG
        bool initialized;
        bool recursive;
#endif
};
 
/*!
 * Init.
 *
 * @public @memberof os_mutex
 */
static inline int
os_mutex_init(struct os_mutex *om)
{
        assert(!om->initialized);
#ifndef NDEBUG
        om->initialized = true;
        om->recursive = false;
#endif
        return pthread_mutex_init(&om->mutex, NULL);
}
 
/*!
 * Lock.
 *
 * @public @memberof os_mutex
 */
static inline void
os_mutex_lock(struct os_mutex *om)
{
        assert(om->initialized);
        pthread_mutex_lock(&om->mutex);
}
 
/*!
 * Try to lock, but do not block.
 *
 * @public @memberof os_mutex
 */
static inline int
os_mutex_trylock(struct os_mutex *om)
{
        assert(om->initialized);
        return pthread_mutex_trylock(&om->mutex);
}
 
/*!
 * Unlock.
 *
 * @public @memberof os_mutex
 */
static inline void
os_mutex_unlock(struct os_mutex *om)
{
        assert(om->initialized);
        pthread_mutex_unlock(&om->mutex);
}
 
/*!
 * Clean up.
 *
 * @public @memberof os_mutex
 */
static inline void
os_mutex_destroy(struct os_mutex *om)
{
        assert(om->initialized);
        assert(!om->recursive);
 
        pthread_mutex_destroy(&om->mutex);
 
#ifndef NDEBUG
        om->initialized = false;
        om->recursive = false;
#endif
}
 
/*!
 * Init.
 *
 * @public @memberof os_mutex
 */
static inline int
os_mutex_recursive_init(struct os_mutex *om)
{
        assert(!om->initialized);
 
#ifndef NDEBUG
        om->initialized = true;
        om->recursive = true;
#endif
 
        pthread_mutexattr_t attr;
        pthread_mutexattr_init(&attr);
        pthread_mutexattr_settype(&attr, PTHREAD_MUTEX_RECURSIVE);
        int ret = pthread_mutex_init(&om->mutex, &attr);
        pthread_mutexattr_destroy(&attr);
 
        return ret;
}
 
/*!
 * Clean up.
 *
 * @public @memberof os_mutex
 */
static inline void
os_mutex_recursive_destroy(struct os_mutex *om)
{
        assert(om->initialized);
        assert(om->recursive);
 
        pthread_mutex_destroy(&om->mutex);
 
#ifndef NDEBUG
        om->initialized = false;
        om->recursive = false;
#endif
}
 
 
/*
 *
 * Conditional variable.
 *
 */
 
/*!
 * A wrapper around a native conditional variable.
 */
struct os_cond
{
        pthread_cond_t cond;
#ifndef NDEBUG
        bool initialized;
#endif
};
 
/*!
 * Init.
 *
 * @public @memberof os_cond
 */
static inline int
os_cond_init(struct os_cond *oc)
{
        assert(!oc->initialized);
#ifndef NDEBUG
        oc->initialized = true;
#endif
        return pthread_cond_init(&oc->cond, NULL);
}
 
/*!
 * Signal.
 *
 * @public @memberof os_cond
 */
static inline void
os_cond_signal(struct os_cond *oc)
{
        assert(oc->initialized);
        pthread_cond_signal(&oc->cond);
}
 
/*!
 * Wait.
 *
 * Be sure to call this in a loop, testing some other condition that you
 * are actually waiting for, as condition variable waits are subject to
 * spurious wakeups.
 *
 * Must be called with the mutex @p om locked.
 *
 * Once the wait begins, the mutex @p om is unlocked, to allow another
 * thread access to change the thing you're monitoring. By the time this
 * returns, you once again own the lock.
 *
 * @public @memberof os_cond
 */
static inline void
os_cond_wait(struct os_cond *oc, struct os_mutex *om)
{
        assert(oc->initialized);
        pthread_cond_wait(&oc->cond, &om->mutex);
}
 
/*!
 * Clean up.
 *
 * @public @memberof os_cond
 */
static inline void
os_cond_destroy(struct os_cond *oc)
{
        assert(oc->initialized);
        pthread_cond_destroy(&oc->cond);
#ifndef NDEBUG
        oc->initialized = false;
#endif
}
 
 
 
/*
 *
 * Thread.
 *
 */
 
/*!
 * A wrapper around a native thread.
 */
struct os_thread
{
        pthread_t thread;
};
 
/*!
 * Run function.
 *
 * @public @memberof os_thread
 */
typedef void *(*os_run_func_t)(void *);
 
/*!
 * Init.
 *
 * @public @memberof os_thread
 */
static inline int
os_thread_init(struct os_thread *ost)
{
        return 0;
}
 
/*!
 * Start thread.
 *
 * @public @memberof os_thread
 */
static inline int
os_thread_start(struct os_thread *ost, os_run_func_t func, void *ptr)
{
        return pthread_create(&ost->thread, NULL, func, ptr);
}
 
/*!
 * Join.
 *
 * @public @memberof os_thread
 */
static inline void
os_thread_join(struct os_thread *ost)
{
        void *retval;
 
        pthread_join(ost->thread, &retval);
        U_ZERO(&ost->thread);
}
 
/*!
 * Destruction.
 *
 * @public @memberof os_thread
 */
static inline void
os_thread_destroy(struct os_thread *ost)
{}
 
/*!
 * Make a best effort to name our thread.
 *
 * @public @memberof os_thread
 */
static inline void
os_thread_name(struct os_thread *ost, const char *name)
{
#ifdef OS_THREAD_HAVE_SETNAME
        pthread_setname_np(ost->thread, name);
#else
        (void)ost;
        (void)name;
#endif
}
 
/*
 *
 * Semaphore.
 *
 */
 
/*!
 * A wrapper around a native semaphore.
 */
struct os_semaphore
{
        sem_t sem;
};
 
/*!
 * Init.
 *
 * @public @memberof os_semaphore
 */
static inline int
os_semaphore_init(struct os_semaphore *os, int count)
{
        return sem_init(&os->sem, 0, count);
}
 
/*!
 * Release.
 *
 * @public @memberof os_semaphore
 */
static inline void
os_semaphore_release(struct os_semaphore *os)
{
        sem_post(&os->sem);
}
 
/*!
 * Set @p ts to the current time, plus the timeout_ns value.
 *
 * Intended for use by the threading code only: the timestamps are not interchangeable with other sources of time.
 *
 * @public @memberof os_semaphore
 */
static inline int
os_semaphore_get_realtime_clock(struct timespec *ts, uint64_t timeout_ns)
{
#if defined(XRT_OS_WINDOWS) && !defined(XRT_ENV_MINGW)
        struct timespec relative;
        os_ns_to_timespec(timeout_ns, &relative);
        pthread_win32_getabstime_np(ts, &relative);
        return 0;
#else
        struct timespec now;
        if (clock_gettime(CLOCK_REALTIME, &now) < 0) {
                assert(false);
                return -1;
        }
        uint64_t now_ns = os_timespec_to_ns(&now);
        uint64_t when_ns = timeout_ns + now_ns;
 
        os_ns_to_timespec(when_ns, ts);
        return 0;
#endif
}
 
/*!
 * Wait, if @p timeout_ns is zero then waits forever.
 *
 * @public @memberof os_semaphore
 */
static inline void
os_semaphore_wait(struct os_semaphore *os, uint64_t timeout_ns)
{
        if (timeout_ns == 0) {
                sem_wait(&os->sem);
                return;
        }
 
        struct timespec abs_timeout;
        if (os_semaphore_get_realtime_clock(&abs_timeout, timeout_ns) == -1) {
                assert(false);
        }
 
        sem_timedwait(&os->sem, &abs_timeout);
}
 
/*!
 * Clean up.
 *
 * @public @memberof os_semaphore
 */
static inline void
os_semaphore_destroy(struct os_semaphore *os)
{
        sem_destroy(&os->sem);
}
 
 
/*
 *
 * Fancy helper.
 *
 */
 
/*!
 * All in one helper that handles locking, waiting for change and starting a
 * thread.
 */
struct os_thread_helper
{
        pthread_t thread;
        pthread_mutex_t mutex;
        pthread_cond_t cond;
 
        bool initialized;
        bool running;
};
 
/*!
 * Initialize the thread helper.
 *
 * @public @memberof os_thread_helper
 */
static inline int
os_thread_helper_init(struct os_thread_helper *oth)
{
        U_ZERO(oth);
 
        int ret = pthread_mutex_init(&oth->mutex, NULL);
        if (ret != 0) {
                return ret;
        }
 
        ret = pthread_cond_init(&oth->cond, NULL);
        if (ret) {
                pthread_mutex_destroy(&oth->mutex);
                return ret;
        }
        oth->initialized = true;
 
        return 0;
}
 
/*!
 * Start the internal thread.
 *
 * @public @memberof os_thread_helper
 */
static inline int
os_thread_helper_start(struct os_thread_helper *oth, os_run_func_t func, void *ptr)
{
        pthread_mutex_lock(&oth->mutex);
 
        assert(oth->initialized);
        if (oth->running) {
                pthread_mutex_unlock(&oth->mutex);
                return -1;
        }
 
        int ret = pthread_create(&oth->thread, NULL, func, ptr);
        if (ret != 0) {
                pthread_mutex_unlock(&oth->mutex);
                return ret;
        }
 
        oth->running = true;
 
        pthread_mutex_unlock(&oth->mutex);
 
        return 0;
}
 
/*!
 * @brief Signal from within the thread that we are stopping.
 *
 * Call with mutex unlocked - it takes and releases the lock internally.
 *
 * @public @memberof os_thread_helper
 */
static inline int
os_thread_helper_signal_stop(struct os_thread_helper *oth)
{
        // The fields are protected.
        pthread_mutex_lock(&oth->mutex);
        assert(oth->initialized);
 
        // Report we're stopping the thread.
        oth->running = false;
 
        // Wake up any waiting thread.
        pthread_cond_signal(&oth->cond);
 
        // No longer need to protect fields.
        pthread_mutex_unlock(&oth->mutex);
 
        return 0;
}
 
/*!
 * @brief Stop the thread and wait for it to exit.
 *
 * Call with mutex unlocked - it takes and releases the lock internally.
 *
 * @public @memberof os_thread_helper
 */
static inline int
os_thread_helper_stop_and_wait(struct os_thread_helper *oth)
{
        void *retval = NULL;
 
        // The fields are protected.
        pthread_mutex_lock(&oth->mutex);
        assert(oth->initialized);
 
        if (!oth->running) {
                // it already exited
                pthread_mutex_unlock(&oth->mutex);
                return 0;
        }
 
        // Stop the thread.
        oth->running = false;
 
        // Wake up the thread if it is waiting.
        pthread_cond_signal(&oth->cond);
 
        // No longer need to protect fields.
        pthread_mutex_unlock(&oth->mutex);
 
        // Wait for thread to finish.
        pthread_join(oth->thread, &retval);
 
        return 0;
}
 
/*!
 * Destroy the thread helper, externally synchronizable.
 *
 * Integrates a call to @ref os_thread_helper_stop_and_wait, so you may just call this for full cleanup
 *
 * @public @memberof os_thread_helper
 */
static inline void
os_thread_helper_destroy(struct os_thread_helper *oth)
{
        assert(oth->initialized);
        // Stop the thread.
        os_thread_helper_stop_and_wait(oth);
 
        // Destroy resources.
        pthread_mutex_destroy(&oth->mutex);
        pthread_cond_destroy(&oth->cond);
        oth->initialized = false;
}
 
/*!
 * Lock the helper.
 *
 * @public @memberof os_thread_helper
 */
static inline void
os_thread_helper_lock(struct os_thread_helper *oth)
{
        pthread_mutex_lock(&oth->mutex);
}
 
/*!
 * Unlock the helper.
 *
 * @public @memberof os_thread_helper
 */
static inline void
os_thread_helper_unlock(struct os_thread_helper *oth)
{
        pthread_mutex_unlock(&oth->mutex);
}
 
/*!
 * Is the thread running, or supposed to be running.
 *
 * Call with mutex unlocked - it takes and releases the lock internally.
 * If you already have a lock, use os_thread_helper_is_running_locked().
 *
 * @public @memberof os_thread_helper
 */
static inline bool
os_thread_helper_is_running(struct os_thread_helper *oth)
{
        os_thread_helper_lock(oth);
        assert(oth->initialized);
        bool ret = oth->running;
        os_thread_helper_unlock(oth);
        return ret;
}
 
/*!
 * Is the thread running, or supposed to be running.
 *
 * Must be called with the helper locked.
 * If you don't have the helper locked for some other reason already,
 * you can use os_thread_helper_is_running()
 *
 * @public @memberof os_thread_helper
 */
static inline bool
os_thread_helper_is_running_locked(struct os_thread_helper *oth)
{
        return oth->running;
}
 
/*!
 * Wait for a signal.
 *
 * Be sure to call this in a loop, testing some other condition that you
 * are actually waiting for, as this is backed by a condition variable
 * wait and is thus subject to spurious wakeups.
 *
 * Must be called with the helper locked.
 *
 * As this wraps a cond-var wait, once the wait begins, the helper is
 * unlocked, to allow another thread access to change the thing you're
 * monitoring. By the time this returns, you once again own the lock.
 *
 * @public @memberof os_thread_helper
 */
static inline void
os_thread_helper_wait_locked(struct os_thread_helper *oth)
{
        pthread_cond_wait(&oth->cond, &oth->mutex);
}
 
/*!
 * Signal a waiting thread to wake up.
 *
 * Must be called with the helper locked.
 *
 * @public @memberof os_thread_helper
 */
static inline void
os_thread_helper_signal_locked(struct os_thread_helper *oth)
{
        pthread_cond_signal(&oth->cond);
}
 
/*!
 * Make a best effort to name our thread.
 *
 * @public @memberof os_thread_helper
 */
static inline void
os_thread_helper_name(struct os_thread_helper *oth, const char *name)
{
#ifdef OS_THREAD_HAVE_SETNAME
        pthread_setname_np(oth->thread, name);
#else
        (void)oth;
        (void)name;
#endif
}
 
/*!
 * @}
 */
 
 
#ifdef __cplusplus
} // extern "C"
#endif
 
 
#ifdef __cplusplus
namespace xrt::auxiliary::os {
 
 
//! A class owning an @ref os_mutex
class Mutex
{
public:
        //! Construct a mutex
        Mutex() noexcept
        {
                os_mutex_init(&inner_);
        }
        //! Destroy a mutex when it goes out of scope
        ~Mutex()
        {
                os_mutex_destroy(&inner_);
        }
 
        //! Block until the lock can be taken.
        void
        lock() noexcept
        {
                os_mutex_lock(&inner_);
        }
 
        //! Take the lock and return true if possible, but do not block
        bool
        try_lock() noexcept
        {
                return 0 == os_mutex_trylock(&inner_);
        }
 
        //! Release the lock
        void
        unlock() noexcept
        {
                os_mutex_unlock(&inner_);
        }
 
        //! Get a pointer to the owned mutex: do not delete it!
        os_mutex *
        get_inner() noexcept
        {
                return &inner_;
        }
 
        // Do not copy or delete these mutexes.
        Mutex(Mutex const &) = delete;
        Mutex(Mutex &&) = delete;
        Mutex &
        operator=(Mutex const &) = delete;
        Mutex &
        operator=(Mutex &&) = delete;
 
private:
        os_mutex inner_{};
};
 
} // namespace xrt::auxiliary::os
 
#endif // __cplusplus