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notifier.cc
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// -*- c-basic-offset: 4; related-file-name: "../include/click/notifier.hh" -*-
/*
* notifier.{cc,hh} -- activity notification
* Eddie Kohler
*
* Copyright (c) 2002 International Computer Science Institute
* Copyright (c) 2004-2005 Regents of the University of California
* Copyright (c) 2008 Meraki, Inc.
* Copyright (c) 2012 Eddie Kohler
*
* Permission is hereby granted, free of charge, to any person obtaining a
* copy of this software and associated documentation files (the "Software"),
* to deal in the Software without restriction, subject to the conditions
* listed in the Click LICENSE file. These conditions include: you must
* preserve this copyright notice, and you cannot mention the copyright
* holders in advertising related to the Software without their permission.
* The Software is provided WITHOUT ANY WARRANTY, EXPRESS OR IMPLIED. This
* notice is a summary of the Click LICENSE file; the license in that file is
* legally binding.
*/
#include <click/config.h>
#if HAVE_CXX_PRAGMA_INTERFACE
# pragma implementation "click/notifier.hh"
#endif
#include <click/notifier.hh>
#include <click/router.hh>
#include <click/element.hh>
#include <click/routervisitor.hh>
#include <click/straccum.hh>
#include <click/bitvector.hh>
CLICK_DECLS
// should be const, but we need to explicitly initialize it
atomic_uint32_t NotifierSignal::static_value;
const char Notifier::EMPTY_NOTIFIER[] = "empty";
const char Notifier::FULL_NOTIFIER[] = "full";
/** @file notifier.hh
* @brief Support for activity signals.
*/
/** @class NotifierSignal
* @brief An activity signal.
*
* Activity signals in Click let one element determine whether another element
* is active. For example, consider an element @e X pulling from a @e Queue.
* If the @e Queue is empty, there's no point in @e X trying to pull from it.
* Thus, the @e Queue has an activity signal that's active when it contains
* packets and inactive when it's empty. @e X can check the activity signal
* before pulling, and do something else if it's inactive. Combined with the
* sleep/wakeup functionality of ActiveNotifier, this can greatly reduce CPU
* load due to polling.
*
* A "basic activity signal" is essentially a bit that's either on or off.
* When it's on, the signal is active. NotifierSignal can represent @e
* derived activity signals as well. A derived signal combines information
* about @e N basic signals using the following invariant: If any of the basic
* signals is active, then the derived signal is also active. There are no
* other guarantees; in particular, the derived signal might be active even if
* @e none of the basic signals are active.
*
* Click elements construct NotifierSignal objects in four ways:
*
* - idle_signal() returns a signal that's never active.
* - busy_signal() returns a signal that's always active.
* - Router::new_notifier_signal() creates a new basic signal. This method
* should be preferred to NotifierSignal's own constructors.
* - operator+(NotifierSignal, const NotifierSignal &) creates a derived signal.
*/
/** @class Notifier
* @brief A basic activity signal and notification provider.
*
* The Notifier class represents a basic activity signal associated with an
* element. Elements that contain a Notifier object will override
* Element::cast() or Element::port_cast() to return that Notifier when given
* the proper name. This lets other parts of the configuration find the
* Notifiers. See upstream_empty_signal() and downstream_full_signal().
*
* The ActiveNotifier class, which derives from Notifier, can wake up clients
* when its activity signal becomes active.
*/
/** @class ActiveNotifier
* @brief A basic activity signal and notification provider that can
* reschedule any dependent Task objects.
*
* ActiveNotifier, whose base class is Notifier, combines a basic activity
* signal with the ability to wake up any dependent Task objects when that
* signal becomes active. Notifier clients are called @e listeners. Each
* listener corresponds to a Task object. The listener generally goes to
* sleep -- i.e., becomes unscheduled -- when it runs out of work and the
* corresponding activity signal is inactive. The ActiveNotifier class will
* wake up the listener when it becomes active by rescheduling the relevant
* Task.
*
* Elements that contain ActiveNotifier objects will generally override
* Element::cast() or Element::port_cast(), allowing other parts of the
* configuration to find the Notifiers.
*/
/** @brief Initialize the NotifierSignal implementation.
*
* This function must be called before NotifierSignal functionality is used.
* It is safe to call it multiple times.
*
* @note Elements don't need to worry about static_initialize(); Click drivers
* have already called it for you.
*/
void
NotifierSignal::static_initialize()
{
static_value = true_mask | overderived_mask;
}
NotifierSignal &
NotifierSignal::operator+=(const NotifierSignal &x)
{
// preserve busy_signal(); adding other incompatible signals
// leads to overderived_signal()
if (idle() || (x.busy() && *this != busy_signal()) || !x.initialized())
*this = x;
else if (busy() || !initialized() || x.idle())
/* do nothing */;
else if (_mask && x._mask && _v.v1 == x._v.v1)
_mask |= x._mask;
else if (x._mask)
hard_derive_one(x._v.v1, x._mask);
else if (this != &x)
for (vmpair *vm = x._v.vm; vm->mask; ++vm)
hard_derive_one(vm->value, vm->mask);
return *this;
}
void
NotifierSignal::hard_assign_vm(const NotifierSignal &x)
{
size_t n = 0;
for (vmpair *vm = x._v.vm; vm->mask; ++vm)
++n;
if (likely((_v.vm = new vmpair[n + 1])))
memcpy(_v.vm, x._v.vm, sizeof(vmpair) * (n + 1));
else {
// cannot call "*this = overderived_signal()" b/c _v.vm is invalid
_v.v1 = &static_value;
_mask = overderived_mask | true_mask;
}
}
void
NotifierSignal::hard_derive_one(atomic_uint32_t *value, uint32_t mask)
{
if (unlikely(_mask)) {
if (busy())
return;
if (_v.v1 == value) {
_mask |= mask;
return;
}
vmpair *vmp;
if (unlikely(!(vmp = new vmpair[2]))) {
*this = overderived_signal();
return;
}
vmp[0].value = _v.v1;
vmp[0].mask = _mask;
vmp[1].mask = 0;
_v.vm = vmp;
_mask = 0;
}
size_t n, i;
vmpair *vmp;
for (i = 0, vmp = _v.vm; vmp->mask && vmp->value < value; ++i, ++vmp)
/* do nothing */;
if (vmp->mask && vmp->value == value) {
vmp->mask |= mask;
return;
}
for (n = i; vmp->mask; ++n, ++vmp)
/* do nothing */;
if (unlikely(!(vmp = new vmpair[n + 2]))) {
*this = overderived_signal();
return;
}
memcpy(vmp, _v.vm, sizeof(vmpair) * i);
memcpy(vmp + i + 1, _v.vm + i, sizeof(vmpair) * (n + 1 - i));
vmp[i].value = value;
vmp[i].mask = mask;
delete[] _v.vm;
_v.vm = vmp;
}
bool
NotifierSignal::hard_equals(const vmpair *a, const vmpair *b)
{
while (a->mask && a->mask == b->mask && a->value == b->value)
++a, ++b;
return !a->mask && a->mask == b->mask;
}
String
NotifierSignal::unparse(Router *router) const
{
if (!_mask) {
StringAccum sa;
for (vmpair *vm = _v.vm; vm->mask; ++vm)
sa << (vm == _v.vm ? "" : "+")
<< NotifierSignal(vm->value, vm->mask).unparse(router);
return sa.take_string();
}
char buf[80];
int pos;
String s;
if (_v.v1 == &static_value) {
if (_mask == true_mask)
return "busy*";
else if (_mask == false_mask)
return "idle";
else if (_mask == overderived_mask)
return "overderived*";
else if (_mask == uninitialized_mask)
return "uninitialized";
else
pos = sprintf(buf, "internal/");
} else if (router && (s = router->notifier_signal_name(_v.v1))) {
pos = sprintf(buf, "%.52s/", s.c_str());
} else
pos = sprintf(buf, "@%p/", _v.v1);
sprintf(buf + pos, active() ? "%x:%x*" : "%x:%x", _mask, (*_v.v1) & _mask);
return String(buf);
}
/** @brief Destruct a Notifier. */
Notifier::~Notifier()
{
}
void
Notifier::dependent_signal_callback(void *user_data, Notifier *)
{
NotifierSignal *signal = static_cast<NotifierSignal *>(user_data);
signal->set_active(true);
}
/** @brief Register an activate callback with this Notifier.
* @param f callback function
* @param user_data callback data for @a f
* @return 1 if notifier was added, 0 on other success, negative on error
*
* When this Notifier's associated signal is activated, this Notifier should
* call @a f(@a user_data, this). Not all types of Notifier provide this
* functionality. The default implementation does nothing.
*
* If @a f is null, then @a user_data is a Task pointer passed to
* add_listener.
*
* @sa remove_activate_callback, add_listener, add_dependent_signal
*/
int
Notifier::add_activate_callback(callback_type f, void *user_data)
{
(void) f, (void) user_data;
return 0;
}
/** @brief Unregister an activate callback with this Notifier.
* @param f callback function
* @param user_data callback data for @a f
*
* Undoes the effect of all prior add_activate_callback(@a f, @a user_data)
* calls. Does nothing if (@a f,@a user_data) was never added. The default
* implementation does nothing.
*
* If @a f is null, then @a user_data is a Task pointer passed to
* remove_listener.
*
* @sa add_activate_callback
*/
void
Notifier::remove_activate_callback(callback_type f, void *user_data)
{
(void) f, (void) user_data;
}
/** @brief Initialize the associated NotifierSignal, if necessary.
* @param name signal name
* @param r associated router
*
* Initialize the Notifier's associated NotifierSignal by calling @a r's
* Router::new_notifier_signal() method, obtaining a new basic activity
* signal. Does nothing if the signal is already initialized.
*/
int
Notifier::initialize(const char *name, Router *r)
{
if (!_signal.initialized())
return r->new_notifier_signal(name, _signal);
else
return 0;
}
/** @brief Construct an ActiveNotifier.
* @param op controls notifier path search
*
* Constructs an ActiveNotifier object, analogous to the
* Notifier::Notifier(SearchOp) constructor. (See that constructor for more
* information on @a op.)
*/
ActiveNotifier::ActiveNotifier(SearchOp op)
: Notifier(op), _listener1(0), _listeners(0)
{
}
/** @brief Destroy an ActiveNotifier. */
ActiveNotifier::~ActiveNotifier()
{
delete[] _listeners;
}
int
ActiveNotifier::add_activate_callback(callback_type f, void *v)
{
// common case
if (!_listener1 && !_listeners && !f) {
_listener1 = static_cast<Task *>(v);
return 1;
}
// count existing listeners
int delta = 1;
task_or_signal_t *tos = _listeners;
for (; tos && tos->p; tos += delta)
if (tos->p == 1) {
delta = 2;
--tos;
} else if ((!f && delta == 1 && tos->t == static_cast<Task *>(v))
|| (f && delta == 2 && tos->f == f && tos[1].v == v))
return 0;
// create new listener array
int n = tos - _listeners + 1;
if (_listener1)
++n;
if (f)
n += (delta == 2 ? 2 : 3);
else
++n;
task_or_signal_t *ntos = new task_or_signal_t[n];
if (!ntos) {
click_chatter("out of memory in Notifier!");
return -ENOMEM;
}
// populate listener array
task_or_signal_t *otos = ntos;
if (_listener1)
(otos++)->t = _listener1;
for (tos = _listeners; tos && tos->p > 1; ++tos)
(otos++)->t = tos->t;
if (!f)
(otos++)->t = static_cast<Task *>(v);
if (f || (tos && tos->p == 1)) {
(otos++)->p = 1;
if (tos && tos->p == 1)
for (++tos; tos->p > 0; ) {
*otos++ = *tos++;
*otos++ = *tos++;
}
if (f) {
(otos++)->f = f;
(otos++)->v = v;
}
}
(otos++)->p = 0;
delete[] _listeners;
_listeners = ntos;
_listener1 = 0;
return 1;
}
void
ActiveNotifier::remove_activate_callback(callback_type f, void *v)
{
if (!f && _listener1 == static_cast<Task *>(v)) {
_listener1 = 0;
return;
}
int delta = 0, step = 1;
task_or_signal_t *tos;
for (tos = _listeners; tos && tos->p; )
if ((!f && step == 1 && tos->t == static_cast<Task *>(v))
|| (f && step == 2 && tos->f == f && tos[1].v == v)) {
delta = -step;
tos += step;
} else {
if (delta)
tos[delta] = *tos;
if (delta && step == 2)
tos[delta + 1] = tos[1];
if (tos->p == 1) {
++tos;
step = 2;
} else
tos += step;
}
if (delta != 0)
tos[delta].p = 0;
}
/** @brief Return the listener list.
* @param[out] v collects listener tasks
*
* Pushes all listener Task objects onto the end of @a v.
*/
void
ActiveNotifier::listeners(Vector<Task*>& v) const
{
if (_listener1)
v.push_back(_listener1);
else if (_listeners)
for (task_or_signal_t* l = _listeners; l->p > 1; ++l)
v.push_back(l->t);
}
#if CLICK_DEBUG_SCHEDULING
String
ActiveNotifier::unparse(Router *router) const
{
StringAccum sa;
sa << signal().unparse(router) << '\n';
if (_listener1 || _listeners)
for (int i = 0; _listener1 ? i == 0 : _listeners[i].p > 1; ++i) {
Task *t = _listener1 ? _listener1 : _listeners[i].t;
sa << "task " << ((void *) t) << ' ';
if (Element *e = t->element())
sa << '[' << e->declaration() << "] ";
sa << (t->scheduled() ? "scheduled\n" : "unscheduled\n");
}
return sa.take_string();
}
#endif
namespace {
class NotifierRouterVisitor : public RouterVisitor { public:
NotifierRouterVisitor(const char* name);
bool visit(Element *e, bool isoutput, int port,
Element *from_e, int from_port, int distance);
Vector<Notifier*> _notifiers;
NotifierSignal _signal;
bool _pass2;
bool _need_pass2;
const char* _name;
};
NotifierRouterVisitor::NotifierRouterVisitor(const char* name)
: _signal(NotifierSignal::idle_signal()),
_pass2(false), _need_pass2(false), _name(name)
{
}
bool
NotifierRouterVisitor::visit(Element* e, bool isoutput, int port,
Element *, int, int)
{
if (Notifier* n = (Notifier*) (e->port_cast(isoutput, port, _name))) {
if (find(_notifiers.begin(), _notifiers.end(), n) == _notifiers.end())
_notifiers.push_back(n);
if (!n->signal().initialized())
n->initialize(_name, e->router());
_signal += n->signal();
Notifier::SearchOp search_op = n->search_op();
if (search_op == Notifier::SEARCH_CONTINUE_WAKE && !_pass2) {
_need_pass2 = true;
return false;
} else
return search_op != Notifier::SEARCH_STOP;
} else if (port >= 0) {
Bitvector flow;
if (e->port_active(isoutput, port)) {
// went from pull <-> push
_signal = NotifierSignal::busy_signal();
return false;
} else if ((e->port_flow(isoutput, port, &flow), flow.zero())
&& e->flag_value('S') != 0) {
// ran out of ports, but element might generate packets
_signal = NotifierSignal::busy_signal();
return false;
} else
return true;
} else
return true;
}
}
/** @brief Calculate and return the NotifierSignal derived from all empty
* notifiers upstream of element @a e's input @a port.
* @param e an element
* @param port the input port of @a e at which to start the upstream search
* @param f callback function
* @param user_data user data for callback function
* @sa add_activate_callback */
NotifierSignal
Notifier::upstream_empty_signal(Element* e, int port, callback_type f, void *user_data)
{
NotifierRouterVisitor filter(EMPTY_NOTIFIER);
int ok = e->router()->visit_upstream(e, port, &filter);
NotifierSignal signal = filter._signal;
// maybe run another pass
if (ok >= 0 && signal != NotifierSignal() && filter._need_pass2) {
filter._pass2 = true;
ok = e->router()->visit_upstream(e, port, &filter);
}
// All bets are off if filter ran into a push output. That means there was
// a regular Queue in the way (for example).
if (ok < 0 || signal == NotifierSignal())
return NotifierSignal();
if (f || user_data)
for (int i = 0; i < filter._notifiers.size(); i++)
filter._notifiers[i]->add_activate_callback(f, user_data);
return signal;
}
/** @brief Calculate and return the NotifierSignal derived from all full
* notifiers downstream of element @a e's output @a port.
* @param e an element
* @param port the output port of @a e at which to start the downstream search
* @param f callback function
* @param user_data user data for callback function
* @sa add_activate_callback */
NotifierSignal
Notifier::downstream_full_signal(Element* e, int port, callback_type f, void *user_data)
{
NotifierRouterVisitor filter(FULL_NOTIFIER);
int ok = e->router()->visit_downstream(e, port, &filter);
NotifierSignal signal = filter._signal;
// maybe run another pass
if (ok >= 0 && signal != NotifierSignal() && filter._need_pass2) {
filter._pass2 = true;
ok = e->router()->visit_downstream(e, port, &filter);
}
// All bets are off if filter ran into a pull input. That means there was
// a regular Queue in the way (for example).
if (ok < 0 || signal == NotifierSignal())
return NotifierSignal();
if (f || user_data)
for (int i = 0; i < filter._notifiers.size(); i++)
filter._notifiers[i]->add_activate_callback(f, user_data);
return signal;
}
CLICK_ENDDECLS