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/* ----------------------------------------------------------------------------
*
* (c) The GHC Team, 2006-2009
*
* Spin locks
*
* These are simple spin-only locks as opposed to Mutexes which
* probably spin for a while before blocking in the kernel. We use
* these when we are sure that all our threads are actively running on
* a CPU, eg. in the GC.
*
* TODO: measure whether we really need these, or whether Mutexes
* would do (and be a bit safer if a CPU becomes loaded).
*
* Do not #include this file directly: #include "Rts.h" instead.
*
* To understand the structure of the RTS headers, see the wiki:
* https://gitlab.haskell.org/ghc/ghc/wikis/commentary/source-tree/includes
*
* -------------------------------------------------------------------------- */
#include "PosixSource.h"
#include "Rts.h"
#if defined(THREADED_RTS)
void acquire_spin_lock_slow_path(SpinLock * p)
{
do {
for (uint32_t i = 0; i < SPIN_COUNT; i++) {
StgWord32 r = cas((StgVolatilePtr)&(p->lock), 1, 0);
if (r != 0) return;
IF_PROF_SPIN(RELAXED_ADD(&p->spin, 1));
busy_wait_nop();
}
IF_PROF_SPIN(RELAXED_ADD(&p->yield, 1));
yieldThread();
} while (1);
}
#endif
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