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#include "SpinLock.h"
// Can adjust for upwards/downwards stack
#define SL_ON_SAME_STACK(stack,ostack) (stack<ostack && stack>ostack-SL_STACK_LOCALITY)
int SpinLock::Enter( ){_CFE_;
int stack = reinterpret_cast<int>(&stack);
int ostack = AtomicExchange( &m_stack, stack );
if( !ostack || // First entry
SL_ON_SAME_STACK(stack,ostack) ) // Repeated entry, same thread
return ostack;
int cnt = SL_MAX_WAIT;
while( cnt-->0 ){
ostack = AtomicExchange( &m_stack, ostack );
if( !ostack ) return 0; // First entry
if( SL_ON_SAME_STACK(stack,ostack) )
return ostack; // Repeated entry, same thread
}
// Failed
return -1;
}
int SpinLock::Leave( int ostack ){_CFE_;
AtomicExchange( (int*)&m_stack, ostack );
return ostack;
}
#define SL_IS_LOCAL(s,v) ((s>v-SL_STACK_LOCALITY) && (s<v+SL_STACK_LOCALITY))
/*
int SpinLock::Enter( ){_CFE_;
SIUINT stack = (int)&stack;
// Are we the owner ?
if( SL_IS_LOCAL(m_stack,stack) ){
SIUINT old_stack = m_stack;
m_stack = stack;
//m_cnt++; // Increase thread count
return (int)old_stack;
}
// Wait until we read back 0, then we can take ownership
int cnt = SL_MAX_WAIT;
SIUINT value;
while( cnt-->0 ) {
value = AtomicExchange( &m_lock, (int)1 );
if( !value ){
// Obtained it
m_stack = stack;
// assert( ++m_cnt==1 );
return 0;
}
}
// Failed
return -1;
}
int SpinLock::Leave( int old_stack ){_CFE_;
m_stack = old_stack;
if( !old_stack )
//if( !--m_cnt )
// Release any waiting thread
AtomicExchange( (int*)&m_lock, 0 );
return old_stack;
}
*/
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