primary_context.hpp

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#ifndef CUDA_API_WRAPPERS_PRIMARY_CONTEXT_HPP_
#define CUDA_API_WRAPPERS_PRIMARY_CONTEXT_HPP_

#include "current_context.hpp"
#include "context.hpp" // A primary context is a context, so can't avoid this

namespace cuda {

namespace device {

class primary_context_t;

namespace primary_context {

namespace detail_ {

struct state_t {
    context::flags_t flags;
    int              is_active; // non-zero value means true
};

inline state_t raw_state(device::id_t device_id)
{
    state_t result;
    auto status = cuDevicePrimaryCtxGetState(device_id, &result.flags, &result.is_active);
    throw_if_error(status, "Failed obtaining the state of the primary context for "
        + device::detail_::identify(device_id));
    // Note: Not sanitizing the flags from having CU_CTX_MAP_HOST set
    return result;
}

inline context::flags_t flags(device::id_t device_id)
{
    return raw_state(device_id).flags & ~CU_CTX_MAP_HOST;
}

inline bool is_active(device::id_t device_id)
{
    return raw_state(device_id).is_active;
}

// We used this wrapper for a one-linear to track PC releases
inline status_t decrease_refcount_nothrow(device::id_t device_id) noexcept
{
    return cuDevicePrimaryCtxRelease(device_id);
}

inline void decrease_refcount(device::id_t device_id)
{
    auto status = decrease_refcount_nothrow(device_id);
    throw_if_error_lazy(status, "Failed releasing the reference to the primary context for " + device::detail_::identify(device_id));
}

// Use this in destructors whose throwing behavior is controlled by the
// preprocessor definition THROW_IN_DESTRUCTORS
inline void decrease_refcount_in_dtor(device::id_t device_id) noexcept
{
#if THROW_IN_DESTRUCTORS
    decrease_refcount(device_id);
#else
    decrease_refcount_nothrow(device_id);
#endif
}

inline handle_t obtain_and_increase_refcount(device::id_t device_id)
{
    handle_t primary_context_handle;
    auto status = cuDevicePrimaryCtxRetain(&primary_context_handle, device_id);
    throw_if_error_lazy(status,
        "Failed obtaining (and possibly creating, and adding a reference count to) the primary context for "
        + device::detail_::identify(device_id));
    return primary_context_handle;
}

inline void increase_refcount(device::id_t device_id)
{
    obtain_and_increase_refcount(device_id);
}

} // namespace detail_

inline bool is_active(const device_t& device);

void destroy(const device_t& device);

namespace detail_ {

inline primary_context_t wrap(
    device::id_t       device_id,
    context::handle_t  handle,
    bool               decrease_refcount_on_destruct) noexcept;

} // namespace detail_

} // namespace primary_context

class primary_context_t : public context_t {

protected: // data members

    bool owns_refcount_unit_;

protected: // constructors

    primary_context_t(
            device::id_t       device_id,
            context::handle_t  handle,
            bool               decrease_refcount_on_destruction) noexcept
    : context_t(device_id, handle, false),
      owns_refcount_unit_(decrease_refcount_on_destruction) { }
        // Note we are _not_ increasing the reference count; we assume
        // the primary context is already active. Also, like any context
        // proxy, we are not making this context current on construction
        // nor expecting it to be current throughout its lifetime.

public:

    stream_t default_stream() const noexcept;

public: // friendship

    friend class ::cuda::device_t;
    friend primary_context_t device::primary_context::detail_::wrap(device::id_t, context::handle_t, bool) noexcept;

public: // constructors and destructor

    primary_context_t(const primary_context_t& other)
    : context_t(other), owns_refcount_unit_(other.owns_refcount_unit_)
    {
        if (owns_refcount_unit_) {
            primary_context::detail_::obtain_and_increase_refcount(device_id_);
        }
    }

    primary_context_t(primary_context_t&& other) noexcept = default;

    ~primary_context_t() DESTRUCTOR_EXCEPTION_SPEC
    {
        if (owns_refcount_unit_) {
            primary_context::detail_::decrease_refcount_in_dtor(device_id_);
        }
    }

public: // operators

    primary_context_t& operator=(const primary_context_t& other) = delete;
    primary_context_t& operator=(primary_context_t&& other) = default;
};

namespace primary_context {

namespace detail_ {

// Note the refcount semantics here, they're a bit tricky
inline context::handle_t get_handle(device::id_t device_id, bool with_refcount_increase = false)
{
    auto handle = obtain_and_increase_refcount(device_id);
    if (not with_refcount_increase) {
        decrease_refcount(device_id);
    }
    return handle;
}

} // namespace detail_

primary_context_t get(const device_t& device);

namespace detail_ {

primary_context_t leaky_get(device::id_t device_id);

// Note that destroying the wrapped instance decreases the refcount,
// meaning that the handle must have been obtained with an "unmatched"
// refcount increase
inline device::primary_context_t wrap(
    id_t      device_id,
    handle_t  handle,
    bool      decrease_refcount_on_destruct) noexcept
{
    return {device_id, handle, decrease_refcount_on_destruct};
}

} // namespace detail_



} // namespace primary_context
} // namespace device

namespace context {

namespace detail_ {

bool is_primary_for_device(handle_t handle, device::id_t device_id);

handle_t get_primary_for_same_device(handle_t handle, bool assume_active = false);


inline bool is_primary(handle_t handle)
{
    return is_primary_for_device(handle, get_device_id(handle));
}

} // namespace detail_

} // namespace context

namespace device {

namespace primary_context {

namespace detail_ {

inline bool is_current(device::id_t device_id)
{
    auto current_context = context::current::detail_::get_handle();
    return context::detail_::is_primary_for_device(current_context, device_id);
}

} // namespace detail

inline bool is_current()
{
    auto device_id = context::current::detail_::get_device_id();
    return detail_::is_current(device_id);
}

} // namespace primary_context

} // namespace device

} // namespace cuda


// Should we want to let the primary context reset itself? That's something which regular
// contexts can't do. We might preclude this, and allow it through the device_t class,
// instead - it already has device_t::reset(), which should be the exact same thing. We
// don't really care if that destroys contexts we're holding on to, because: 1. It won't
// cause segmentation violations - we're not dereferencing freed pointers and 2. it's the
// user's problem, not ours.


#endif /* CUDA_API_WRAPPERS_PRIMARY_CONTEXT_HPP_ */