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fix shared loop: in rare cases elements have been called twice

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This commit is contained in:
Joachim Schoeberl 2022-04-30 10:39:26 +02:00
parent aa00749f97
commit bf22f8d4df
1 changed files with 37 additions and 12 deletions
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49
libsrc/core/taskmanager.hpp
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@ -464,23 +464,26 @@ public:
bool PopFirst (size_t & first)
{
first = begin++;
return first < end;
/*
// int oldbegin = begin;
size_t oldbegin = begin.load(std::memory_order_acquire);
if (oldbegin >= end) return false;
while (!begin.compare_exchange_weak (oldbegin, oldbegin+1,
std::memory_order_relaxed, std::memory_order_relaxed))
if (oldbegin >= end) return false;
// first = begin++;
// return first < end;
first = oldbegin;
return true;
*/
first = begin;
size_t nextfirst = first+1;
if (first >= end) nextfirst = std::numeric_limits<size_t>::max()-1;
while (!begin.compare_exchange_weak (first, nextfirst))
{
first = begin;
nextfirst = first+1;
if (nextfirst >= end) nextfirst = std::numeric_limits<size_t>::max()-1;
}
return first < end;
}
bool PopHalf (IntRange & r)
{
/*
// int oldbegin = begin;
size_t oldbegin = begin.load(std::memory_order_acquire);
size_t oldend = end.load(std::memory_order_acquire);
@ -496,6 +499,28 @@ public:
r = IntRange(oldbegin, (oldbegin+oldend+1)/2);
return true;
*/
size_t oldbegin = begin; // .load(std::memory_order_acquire);
size_t oldend = end; // .load(std::memory_order_acquire);
if (oldbegin >= oldend) return false;
size_t nextbegin = (oldbegin+oldend+1)/2;
if (nextbegin >= oldend) nextbegin = std::numeric_limits<size_t>::max()-1;
while (!begin.compare_exchange_weak (oldbegin, nextbegin))
// std::memory_order_relaxed, std::memory_order_relaxed))
{
oldend = end; // .load(std::memory_order_acquire);
if (oldbegin >= oldend) return false;
nextbegin = (oldbegin+oldend+1)/2;
if (nextbegin >= oldend) nextbegin = std::numeric_limits<size_t>::max()-1;
}
r = IntRange(oldbegin, (oldbegin+oldend+1)/2);
return true;
}
};