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Code Issues Releases Wiki Activity

ircd::ctx: Candidate fixes for view sequencing.

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This commit is contained in:
Jason Volk 2018-03-27 01:34:35 -07:00
parent b49cdb84e8
commit 543a1988b9
1 changed files with 50 additions and 40 deletions
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90
include/ircd/ctx/view.h
View file

@ -36,8 +36,9 @@ template<class T,
class ircd::ctx::view
:public mutex
{
T *t {nullptr};
dock q;
T *t {nullptr};
size_t wanting {0};
size_t waiting {0};
bool ready() const;
@ -61,6 +62,7 @@ ircd::ctx::view<T, mutex>::~view()
noexcept
{
assert(!waiting);
assert(!wanting);
}
template<class T,
@ -68,16 +70,21 @@ template<class T,
void
ircd::ctx::view<T, mutex>::operator()(T &t)
{
if(!waiting)
return;
const auto produce{[this]
(T *const &t, size_t &semaphore)
{
q.wait([this, &semaphore]
{
return semaphore == 0;
});
this->t = &t;
q.notify_all();
q.wait([this] { return !waiting; });
const std::lock_guard<view> lock{*this};
this->t = nullptr;
assert(!waiting);
q.notify_all();
const std::lock_guard<view> lock{*this};
this->t = t;
q.notify_all();
}};
produce(&t, wanting);
produce(nullptr, waiting);
}
template<class T,
@ -86,24 +93,26 @@ template<class lock>
T &
ircd::ctx::view<T, mutex>::wait(lock &l)
{
for(assert(l.owns_lock()); ready(); l.lock())
const auto consume{[this, &l]
(const bool &r, size_t &semaphore)
{
l.unlock();
q.wait();
}
const unwind uw{[this, &l, &semaphore]
{
--semaphore;
q.notify_all();
}};
const unwind ul{[this]
{
--waiting;
q.notify_all();
++semaphore;
assert(l.owns_lock());
const unlock_guard<lock> ul{l};
q.wait([this, &r]
{
return ready() == r;
});
}};
for(++waiting; !ready(); l.lock())
{
l.unlock();
q.wait();
}
consume(false, wanting);
consume(true, waiting);
assert(t != nullptr);
return *t;
}
@ -127,26 +136,27 @@ T &
ircd::ctx::view<T, mutex>::wait_until(lock &l,
time_point&& tp)
{
for(assert(l.owns_lock()); ready(); l.lock())
const auto consume{[this, &l, &tp]
(const bool &r, size_t &semaphore)
{
l.unlock();
if(!q.wait_until(tp))
throw timeout{};
}
const unwind uw{[this, &l, &semaphore]
{
--semaphore;
q.notify_all();
}};
const unwind ul{[this]
{
--waiting;
q.notify_all();
++semaphore;
assert(l.owns_lock());
const unlock_guard<lock> ul{l};
if(!q.wait_until(tp, [this, &r]
{
return ready() == r;
}))
throw timeout{};
}};
for(++waiting; !ready(); l.lock())
{
l.unlock();
if(!q.wait_until(tp))
throw timeout{};
}
consume(false, wanting);
consume(true, waiting);
assert(t != nullptr);
return *t;
}