zircon/system/ulib/dispatcher-pool/dispatcher-interrupt.cpp

// Copyright 2017 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include <zircon/syscalls.h>
#include <zircon/types.h>
#include <lib/zx/timer.h>

#include <dispatcher-pool/dispatcher-execution-domain.h>
#include <dispatcher-pool/dispatcher-interrupt.h>
#include <dispatcher-pool/dispatcher-thread-pool.h>

#include <utility>

namespace dispatcher {

// static
fbl::RefPtr<Interrupt> Interrupt::Create() {
    fbl::AllocChecker ac;

    auto ptr = new (&ac) Interrupt();
    if (!ac.check()) {
        return nullptr;
    }

    return fbl::AdoptRef(ptr);
}

zx_status_t Interrupt::Activate(fbl::RefPtr<ExecutionDomain> domain,
                                zx::interrupt irq,
                                ProcessHandler process_handler) {
    if (process_handler == nullptr) {
        return ZX_ERR_INVALID_ARGS;
    }

    fbl::AutoLock obj_lock(&obj_lock_);

    zx_status_t res = ActivateLocked(std::move(irq), std::move(domain));
    if (res != ZX_OK) {
        return res;
    }

    res = WaitOnPortLocked();
    if (res != ZX_OK) {
        InternalDeactivateLocked();
        return res;
    }

    process_handler_ = std::move(process_handler);

    return ZX_OK;
}

void Interrupt::Deactivate() {
    ProcessHandler old_process_handler;

    {
        fbl::AutoLock obj_lock(&obj_lock_);
        InternalDeactivateLocked();

        // If we are in the process of actively dispatching, do not discard our
        // handler just yet.  It is currently being used by the dispatch thread.
        // Instead, wait until the dispatch thread unwinds and allow it to clean
        // up the handler.
        //
        // Otherwise, transfer the handler state into local storage and let it
        // destruct after we have released the object lock.
        if (dispatch_state() != DispatchState::Dispatching) {
            ZX_DEBUG_ASSERT((dispatch_state() == DispatchState::Idle) ||
                            (dispatch_state() == DispatchState::WaitingOnPort));
            old_process_handler = std::move(process_handler_);
        }
    }
}

void Interrupt::Dispatch(ExecutionDomain* domain) {
    ZX_DEBUG_ASSERT(domain != nullptr);
    ZX_DEBUG_ASSERT(process_handler_ != nullptr);
    ZX_DEBUG_ASSERT(pending_pkt_.type == ZX_PKT_TYPE_INTERRUPT);

    zx_status_t res = process_handler_(this, pending_pkt_.interrupt.timestamp);
    ProcessHandler old_process_handler;
    {
        fbl::AutoLock obj_lock(&obj_lock_);
        ZX_DEBUG_ASSERT(dispatch_state() == DispatchState::Dispatching);
        dispatch_state_ = DispatchState::Idle;

        // Was there a problem during processing?  If so, make sure that we
        // de-activate ourselves.
        if (res != ZX_OK) {
            InternalDeactivateLocked();
        }

        // Are we still active?  If so, ack the interrupt so that it can produce
        // new messages.
        if (is_active()) {
            res = WaitOnPortLocked();

            if (res != ZX_OK) {
                dispatch_state_ = DispatchState::Idle;
                InternalDeactivateLocked();
            }
        }

        // Have we become deactivated (either during dispatching or just now)?
        // If so, move our process handler state outside of our lock so that it
        // can safely destruct.
        if (!is_active()) {
            old_process_handler = std::move(process_handler_);
        }
    }
}

zx_status_t Interrupt::DoPortWaitLocked() {
    // Interrupt Event Sources are a bit different from other event sources
    // because of the differences in how zircon handles associating a physical
    // interrupt with a port as compared to other handles..
    //
    // Zircon allows an interrupt to be bound to a port once, at which point in
    // time it remains bound to the port until it is destroyed.  There is no way
    // to "unbind" an interrupt from a port without destroying the interrupt
    // object with an explicit call to zx_interrupt_destroy.
    //
    // When a zircon interrupt fires while bound to a port, it posts a message
    // to the port.  It then will not post any further messages to the port
    // until zx_interrupt_ack is explicitly called.
    //
    // So, when an Interrupt event source in the dispatcher-pool framework
    // becomes activated, the first time we "wait-on-port" results in a call to
    // zx_interrupt_bind (via the ThreadPool's BindIrqToPort).  Subsequently,
    // every time that an interrupt fires and is dispatched, we call
    // zx_interrupt_ack as part of unwinding after dispatch is complete,
    // assuming that both execution domain and the interrupt event source are
    // still active.
    //
    // The only time that an interrupt event source is canceled
    // (DoPortCancelLocked) is as a side effect of de-activation, either because
    // the specific event source is being shut down, or because the entire
    // execution domain is being shut down.  If a method were to be introduced
    // to allow users to require manual re-arming of an interrupt event source,
    // new state would need to be introduced to the Interrupt object to allow
    // for this.

    zx_status_t res;
    if (irq_bound_) {
        // If we have already been bound, then ack the interrupt it order to
        // cause it to become re-armed.
        res = zx_interrupt_ack(handle_.get());
    } else {
        // We have not yet been bound, do so now.
        ZX_DEBUG_ASSERT(thread_pool_ != nullptr);
        res = thread_pool_->BindIrqToPort(handle_, reinterpret_cast<uint64_t>(this));
        if (res == ZX_OK) {
            irq_bound_ = true;
        }
    }

    return res;
}

zx_status_t Interrupt::DoPortCancelLocked() {
    return zx_interrupt_destroy(handle_.get());
}

}  // namespace dispatcher