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Commitb64d92f

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Add a basic atomic ops API abstracting away platform/architecture details.
Several upcoming performance/scalability improvements require atomicoperations. This new API avoids the need to splatter compiler andarchitecture dependent code over all the locations employing atomicops.For several of the potential usages it'd be problematic to maintainboth, a atomics using implementation and one using spinlocks orsimilar. In all likelihood one of the implementations would not gettested regularly under concurrency. To avoid that scenario the new APIprovides a automatic fallback of atomic operations to spinlocks. Allproperties of atomic operations are maintained. This fallback -obviously - isn't as fast as just using atomic ops, but it's not badeither. For one of the future users the atomics ontop spinlocksimplementation was actually slightly faster than the old purelyspinlock using implementation. That's important because it reduces thefear of regressing older platforms when improving the scalability fornew ones.The API, loosely modeled after the C11 atomics support, currentlyprovides 'atomic flags' and 32 bit unsigned integers. If the platformefficiently supports atomic 64 bit unsigned integers those are alsoprovided.To implement atomics support for a platform/architecture/compiler fora type of atomics 32bit compare and exchange needs to beimplemented. If available and more efficient native support for flags,32 bit atomic addition, and corresponding 64 bit operations may alsobe provided. Additional useful atomic operations are implementedgenerically ontop of these.The implementation for various versions of gcc, msvc and sun studio havebeen tested. Additional existing stub implementations for* Intel icc* HUPX acc* IBM xlcare included but have never been tested. These will likely requirefixes based on buildfarm and user feedback.As atomic operations also require barriers for some operations theexisting barrier support has been moved into the atomics code.Author: Andres Freund with contributions from Oskari SaarenmaaReviewed-By: Amit Kapila, Robert Haas, Heikki Linnakangas and Álvaro HerreraDiscussion: CA+TgmoYBW+ux5-8Ja=Mcyuy8=VXAnVRHp3Kess6Pn3DMXAPAEA@mail.gmail.com, 20131015123303.GH5300@awork2.anarazel.de, 20131028205522.GI20248@awork2.anarazel.de
1 parent9111d46 commitb64d92f

31 files changed

+2816
-208
lines changed

‎config/c-compiler.m4

Lines changed: 98 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -300,3 +300,101 @@ if test x"$Ac_cachevar" = x"yes"; then
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fi
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undefine([Ac_cachevar])dnl
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])# PGAC_PROG_CC_LDFLAGS_OPT
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# PGAC_HAVE_GCC__SYNC_CHAR_TAS
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# -------------------------
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# Check if the C compiler understands __sync_lock_test_and_set(char),
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# and define HAVE_GCC__SYNC_CHAR_TAS
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#
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# NB: There are platforms where test_and_set is available but compare_and_swap
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# is not, so test this separately.
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# NB: Some platforms only do 32bit tas, others only do 8bit tas. Test both.
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AC_DEFUN([PGAC_HAVE_GCC__SYNC_CHAR_TAS],
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[AC_CACHE_CHECK(forbuiltin__synccharlockingfunctions,pgac_cv_gcc_sync_char_tas,
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[AC_TRY_LINK([],
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[char lock = 0;
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__sync_lock_test_and_set(&lock, 1);
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__sync_lock_release(&lock);],
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[pgac_cv_gcc_sync_char_tas="yes"],
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[pgac_cv_gcc_sync_char_tas="no"])])
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if test x"$pgac_cv_gcc_sync_char_tas" = x"yes"; then
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AC_DEFINE(HAVE_GCC__SYNC_CHAR_TAS,1,[Define to 1 if you have __sync_lock_test_and_set(char *) and friends.])
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fi])# PGAC_HAVE_GCC__SYNC_CHAR_TAS
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# PGAC_HAVE_GCC__SYNC_INT32_TAS
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# -------------------------
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# Check if the C compiler understands __sync_lock_test_and_set(),
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# and define HAVE_GCC__SYNC_INT32_TAS
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AC_DEFUN([PGAC_HAVE_GCC__SYNC_INT32_TAS],
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[AC_CACHE_CHECK(forbuiltin__syncint32lockingfunctions,pgac_cv_gcc_sync_int32_tas,
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[AC_TRY_LINK([],
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[int lock = 0;
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__sync_lock_test_and_set(&lock, 1);
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__sync_lock_release(&lock);],
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[pgac_cv_gcc_sync_int32_tas="yes"],
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[pgac_cv_gcc_sync_int32_tas="no"])])
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if test x"$pgac_cv_gcc_sync_int32_tas" = x"yes"; then
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AC_DEFINE(HAVE_GCC__SYNC_INT32_TAS,1,[Define to 1 if you have __sync_lock_test_and_set(int *) and friends.])
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fi])# PGAC_HAVE_GCC__SYNC_INT32_TAS
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# PGAC_HAVE_GCC__SYNC_INT32_CAS
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# -------------------------
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# Check if the C compiler understands __sync_compare_and_swap() for 32bit
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# types, and define HAVE_GCC__SYNC_INT32_CAS if so.
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AC_DEFUN([PGAC_HAVE_GCC__SYNC_INT32_CAS],
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[AC_CACHE_CHECK(forbuiltin__syncint32atomicoperations,pgac_cv_gcc_sync_int32_cas,
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[AC_TRY_LINK([],
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[int val = 0;
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__sync_val_compare_and_swap(&val, 0, 37);],
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[pgac_cv_gcc_sync_int32_cas="yes"],
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[pgac_cv_gcc_sync_int32_cas="no"])])
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if test x"$pgac_cv_gcc_sync_int32_cas" = x"yes"; then
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AC_DEFINE(HAVE_GCC__SYNC_INT32_CAS,1,[Define to 1 if you have __sync_compare_and_swap(int *, int, int).])
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fi])# PGAC_HAVE_GCC__SYNC_INT32_CAS
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# PGAC_HAVE_GCC__SYNC_INT64_CAS
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# -------------------------
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# Check if the C compiler understands __sync_compare_and_swap() for 64bit
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# types, and define HAVE_GCC__SYNC_INT64_CAS if so.
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AC_DEFUN([PGAC_HAVE_GCC__SYNC_INT64_CAS],
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[AC_CACHE_CHECK(forbuiltin__syncint64atomicoperations,pgac_cv_gcc_sync_int64_cas,
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[AC_TRY_LINK([],
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[PG_INT64_TYPE lock = 0;
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__sync_val_compare_and_swap(&lock, 0, (PG_INT64_TYPE) 37);],
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[pgac_cv_gcc_sync_int64_cas="yes"],
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[pgac_cv_gcc_sync_int64_cas="no"])])
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if test x"$pgac_cv_gcc_sync_int64_cas" = x"yes"; then
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AC_DEFINE(HAVE_GCC__SYNC_INT64_CAS,1,[Define to 1 if you have __sync_compare_and_swap(int64 *, int64, int64).])
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fi])# PGAC_HAVE_GCC__SYNC_INT64_CAS
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# PGAC_HAVE_GCC__ATOMIC_INT32_CAS
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# -------------------------
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# Check if the C compiler understands __atomic_compare_exchange_n() for 32bit
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# types, and define HAVE_GCC__ATOMIC_INT32_CAS if so.
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AC_DEFUN([PGAC_HAVE_GCC__ATOMIC_INT32_CAS],
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[AC_CACHE_CHECK(forbuiltin__atomicint32atomicoperations,pgac_cv_gcc_atomic_int32_cas,
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[AC_TRY_LINK([],
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[int val = 0;
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int expect = 0;
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__atomic_compare_exchange_n(&val, &expect, 37, 0, __ATOMIC_SEQ_CST, __ATOMIC_RELAXED);],
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[pgac_cv_gcc_atomic_int32_cas="yes"],
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[pgac_cv_gcc_atomic_int32_cas="no"])])
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if test x"$pgac_cv_gcc_atomic_int32_cas" = x"yes"; then
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AC_DEFINE(HAVE_GCC__ATOMIC_INT32_CAS,1,[Define to 1 if you have __atomic_compare_exchange_n(int *, int *, int).])
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fi])# PGAC_HAVE_GCC__ATOMIC_INT32_CAS
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# PGAC_HAVE_GCC__ATOMIC_INT64_CAS
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# -------------------------
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# Check if the C compiler understands __atomic_compare_exchange_n() for 64bit
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# types, and define HAVE_GCC__ATOMIC_INT64_CAS if so.
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AC_DEFUN([PGAC_HAVE_GCC__ATOMIC_INT64_CAS],
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[AC_CACHE_CHECK(forbuiltin__atomicint64atomicoperations,pgac_cv_gcc_atomic_int64_cas,
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[AC_TRY_LINK([],
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[PG_INT64_TYPE val = 0;
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PG_INT64_TYPE expect = 0;
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__atomic_compare_exchange_n(&val, &expect, 37, 0, __ATOMIC_SEQ_CST, __ATOMIC_RELAXED);],
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[pgac_cv_gcc_atomic_int64_cas="yes"],
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[pgac_cv_gcc_atomic_int64_cas="no"])])
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if test x"$pgac_cv_gcc_atomic_int64_cas" = x"yes"; then
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AC_DEFINE(HAVE_GCC__ATOMIC_INT64_CAS,1,[Define to 1 if you have __atomic_compare_exchange_n(int64 *, int *, int64).])
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fi])# PGAC_HAVE_GCC__ATOMIC_INT64_CAS

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