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improve spinlock code

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This commit is contained in:
Oliver Kowalke
2015-01-10 21:21:36 +01:00
parent 9b7b0be903
commit bfde9ecae6
1 changed files with 7 additions and 13 deletions
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20
src/detail/spinlock.cpp
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@@ -22,25 +22,19 @@ spinlock::spinlock() :
void
spinlock::lock()
{
for (;;)
{
do {
// access to CPU's cache
// first access to state_ -> cache miss
// sucessive acccess to state_ > cache hit
while ( LOCKED == state_)
{
// sucessive acccess to state_ -> cache hit
while ( LOCKED == state_.load( boost::memory_order_relaxed) ) {
// busy-wait
if ( 0 != fm_active() )
fm_yield();
else
this_thread::yield();
fm_yield();
}
// state_ was released by other
// state_ was released by other fiber
// cached copies are invalidated -> cache miss
// test-and-set over the bus
if ( UNLOCKED == state_.exchange( LOCKED) )
return;
// test-and-set signaled over the bus
}
while ( UNLOCKED != state_.exchange( LOCKED, boost::memory_order_acquire) );
}
void