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Diffstat (limited to 'src/include/storage/s_lock.h')
| -rw-r--r-- | src/include/storage/s_lock.h | 1071 |
1 files changed, 1071 insertions, 0 deletions
diff --git a/src/include/storage/s_lock.h b/src/include/storage/s_lock.h new file mode 100644 index 0000000..dccbd29 --- /dev/null +++ b/src/include/storage/s_lock.h @@ -0,0 +1,1071 @@ +/*------------------------------------------------------------------------- + * + * s_lock.h + * Hardware-dependent implementation of spinlocks. + * + * NOTE: none of the macros in this file are intended to be called directly. + * Call them through the hardware-independent macros in spin.h. + * + * The following hardware-dependent macros must be provided for each + * supported platform: + * + * void S_INIT_LOCK(slock_t *lock) + * Initialize a spinlock (to the unlocked state). + * + * int S_LOCK(slock_t *lock) + * Acquire a spinlock, waiting if necessary. + * Time out and abort() if unable to acquire the lock in a + * "reasonable" amount of time --- typically ~ 1 minute. + * Should return number of "delays"; see s_lock.c + * + * void S_UNLOCK(slock_t *lock) + * Unlock a previously acquired lock. + * + * bool S_LOCK_FREE(slock_t *lock) + * Tests if the lock is free. Returns true if free, false if locked. + * This does *not* change the state of the lock. + * + * void SPIN_DELAY(void) + * Delay operation to occur inside spinlock wait loop. + * + * Note to implementors: there are default implementations for all these + * macros at the bottom of the file. Check if your platform can use + * these or needs to override them. + * + * Usually, S_LOCK() is implemented in terms of even lower-level macros + * TAS() and TAS_SPIN(): + * + * int TAS(slock_t *lock) + * Atomic test-and-set instruction. Attempt to acquire the lock, + * but do *not* wait. Returns 0 if successful, nonzero if unable + * to acquire the lock. + * + * int TAS_SPIN(slock_t *lock) + * Like TAS(), but this version is used when waiting for a lock + * previously found to be contended. By default, this is the + * same as TAS(), but on some architectures it's better to poll a + * contended lock using an unlocked instruction and retry the + * atomic test-and-set only when it appears free. + * + * TAS() and TAS_SPIN() are NOT part of the API, and should never be called + * directly. + * + * CAUTION: on some platforms TAS() and/or TAS_SPIN() may sometimes report + * failure to acquire a lock even when the lock is not locked. For example, + * on Alpha TAS() will "fail" if interrupted. Therefore a retry loop must + * always be used, even if you are certain the lock is free. + * + * It is the responsibility of these macros to make sure that the compiler + * does not re-order accesses to shared memory to precede the actual lock + * acquisition, or follow the lock release. Prior to PostgreSQL 9.5, this + * was the caller's responsibility, which meant that callers had to use + * volatile-qualified pointers to refer to both the spinlock itself and the + * shared data being accessed within the spinlocked critical section. This + * was notationally awkward, easy to forget (and thus error-prone), and + * prevented some useful compiler optimizations. For these reasons, we + * now require that the macros themselves prevent compiler re-ordering, + * so that the caller doesn't need to take special precautions. + * + * On platforms with weak memory ordering, the TAS(), TAS_SPIN(), and + * S_UNLOCK() macros must further include hardware-level memory fence + * instructions to prevent similar re-ordering at the hardware level. + * TAS() and TAS_SPIN() must guarantee that loads and stores issued after + * the macro are not executed until the lock has been obtained. Conversely, + * S_UNLOCK() must guarantee that loads and stores issued before the macro + * have been executed before the lock is released. + * + * On most supported platforms, TAS() uses a tas() function written + * in assembly language to execute a hardware atomic-test-and-set + * instruction. Equivalent OS-supplied mutex routines could be used too. + * + * If no system-specific TAS() is available (ie, HAVE_SPINLOCKS is not + * defined), then we fall back on an emulation that uses SysV semaphores + * (see spin.c). This emulation will be MUCH MUCH slower than a proper TAS() + * implementation, because of the cost of a kernel call per lock or unlock. + * An old report is that Postgres spends around 40% of its time in semop(2) + * when using the SysV semaphore code. + * + * + * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group + * Portions Copyright (c) 1994, Regents of the University of California + * + * src/include/storage/s_lock.h + * + *------------------------------------------------------------------------- + */ +#ifndef S_LOCK_H +#define S_LOCK_H + +#ifdef FRONTEND +#error "s_lock.h may not be included from frontend code" +#endif + +#ifdef HAVE_SPINLOCKS /* skip spinlocks if requested */ + +#if defined(__GNUC__) || defined(__INTEL_COMPILER) +/************************************************************************* + * All the gcc inlines + * Gcc consistently defines the CPU as __cpu__. + * Other compilers use __cpu or __cpu__ so we test for both in those cases. + */ + +/*---------- + * Standard gcc asm format (assuming "volatile slock_t *lock"): + + __asm__ __volatile__( + " instruction \n" + " instruction \n" + " instruction \n" +: "=r"(_res), "+m"(*lock) // return register, in/out lock value +: "r"(lock) // lock pointer, in input register +: "memory", "cc"); // show clobbered registers here + + * The output-operands list (after first colon) should always include + * "+m"(*lock), whether or not the asm code actually refers to this + * operand directly. This ensures that gcc believes the value in the + * lock variable is used and set by the asm code. Also, the clobbers + * list (after third colon) should always include "memory"; this prevents + * gcc from thinking it can cache the values of shared-memory fields + * across the asm code. Add "cc" if your asm code changes the condition + * code register, and also list any temp registers the code uses. + *---------- + */ + + +#ifdef __i386__ /* 32-bit i386 */ +#define HAS_TEST_AND_SET + +typedef unsigned char slock_t; + +#define TAS(lock) tas(lock) + +static __inline__ int +tas(volatile slock_t *lock) +{ + register slock_t _res = 1; + + /* + * Use a non-locking test before asserting the bus lock. Note that the + * extra test appears to be a small loss on some x86 platforms and a small + * win on others; it's by no means clear that we should keep it. + * + * When this was last tested, we didn't have separate TAS() and TAS_SPIN() + * macros. Nowadays it probably would be better to do a non-locking test + * in TAS_SPIN() but not in TAS(), like on x86_64, but no-one's done the + * testing to verify that. Without some empirical evidence, better to + * leave it alone. + */ + __asm__ __volatile__( + " cmpb $0,%1 \n" + " jne 1f \n" + " lock \n" + " xchgb %0,%1 \n" + "1: \n" +: "+q"(_res), "+m"(*lock) +: /* no inputs */ +: "memory", "cc"); + return (int) _res; +} + +#define SPIN_DELAY() spin_delay() + +static __inline__ void +spin_delay(void) +{ + /* + * This sequence is equivalent to the PAUSE instruction ("rep" is + * ignored by old IA32 processors if the following instruction is + * not a string operation); the IA-32 Architecture Software + * Developer's Manual, Vol. 3, Section 7.7.2 describes why using + * PAUSE in the inner loop of a spin lock is necessary for good + * performance: + * + * The PAUSE instruction improves the performance of IA-32 + * processors supporting Hyper-Threading Technology when + * executing spin-wait loops and other routines where one + * thread is accessing a shared lock or semaphore in a tight + * polling loop. When executing a spin-wait loop, the + * processor can suffer a severe performance penalty when + * exiting the loop because it detects a possible memory order + * violation and flushes the core processor's pipeline. The + * PAUSE instruction provides a hint to the processor that the + * code sequence is a spin-wait loop. The processor uses this + * hint to avoid the memory order violation and prevent the + * pipeline flush. In addition, the PAUSE instruction + * de-pipelines the spin-wait loop to prevent it from + * consuming execution resources excessively. + */ + __asm__ __volatile__( + " rep; nop \n"); +} + +#endif /* __i386__ */ + + +#ifdef __x86_64__ /* AMD Opteron, Intel EM64T */ +#define HAS_TEST_AND_SET + +typedef unsigned char slock_t; + +#define TAS(lock) tas(lock) + +/* + * On Intel EM64T, it's a win to use a non-locking test before the xchg proper, + * but only when spinning. + * + * See also Implementing Scalable Atomic Locks for Multi-Core Intel(tm) EM64T + * and IA32, by Michael Chynoweth and Mary R. Lee. As of this writing, it is + * available at: + * http://software.intel.com/en-us/articles/implementing-scalable-atomic-locks-for-multi-core-intel-em64t-and-ia32-architectures + */ +#define TAS_SPIN(lock) (*(lock) ? 1 : TAS(lock)) + +static __inline__ int +tas(volatile slock_t *lock) +{ + register slock_t _res = 1; + + __asm__ __volatile__( + " lock \n" + " xchgb %0,%1 \n" +: "+q"(_res), "+m"(*lock) +: /* no inputs */ +: "memory", "cc"); + return (int) _res; +} + +#define SPIN_DELAY() spin_delay() + +static __inline__ void +spin_delay(void) +{ + /* + * Adding a PAUSE in the spin delay loop is demonstrably a no-op on + * Opteron, but it may be of some use on EM64T, so we keep it. + */ + __asm__ __volatile__( + " rep; nop \n"); +} + +#endif /* __x86_64__ */ + + +#if defined(__ia64__) || defined(__ia64) +/* + * Intel Itanium, gcc or Intel's compiler. + * + * Itanium has weak memory ordering, but we rely on the compiler to enforce + * strict ordering of accesses to volatile data. In particular, while the + * xchg instruction implicitly acts as a memory barrier with 'acquire' + * semantics, we do not have an explicit memory fence instruction in the + * S_UNLOCK macro. We use a regular assignment to clear the spinlock, and + * trust that the compiler marks the generated store instruction with the + * ".rel" opcode. + * + * Testing shows that assumption to hold on gcc, although I could not find + * any explicit statement on that in the gcc manual. In Intel's compiler, + * the -m[no-]serialize-volatile option controls that, and testing shows that + * it is enabled by default. + * + * While icc accepts gcc asm blocks on x86[_64], this is not true on ia64 + * (at least not in icc versions before 12.x). So we have to carry a separate + * compiler-intrinsic-based implementation for it. + */ +#define HAS_TEST_AND_SET + +typedef unsigned int slock_t; + +#define TAS(lock) tas(lock) + +/* On IA64, it's a win to use a non-locking test before the xchg proper */ +#define TAS_SPIN(lock) (*(lock) ? 1 : TAS(lock)) + +#ifndef __INTEL_COMPILER + +static __inline__ int +tas(volatile slock_t *lock) +{ + long int ret; + + __asm__ __volatile__( + " xchg4 %0=%1,%2 \n" +: "=r"(ret), "+m"(*lock) +: "r"(1) +: "memory"); + return (int) ret; +} + +#else /* __INTEL_COMPILER */ + +static __inline__ int +tas(volatile slock_t *lock) +{ + int ret; + + ret = _InterlockedExchange(lock,1); /* this is a xchg asm macro */ + + return ret; +} + +/* icc can't use the regular gcc S_UNLOCK() macro either in this case */ +#define S_UNLOCK(lock) \ + do { __memory_barrier(); *(lock) = 0; } while (0) + +#endif /* __INTEL_COMPILER */ +#endif /* __ia64__ || __ia64 */ + + +/* + * On ARM and ARM64, we use __sync_lock_test_and_set(int *, int) if available. + * + * We use the int-width variant of the builtin because it works on more chips + * than other widths. + */ +#if defined(__arm__) || defined(__arm) || defined(__aarch64__) || defined(__aarch64) +#ifdef HAVE_GCC__SYNC_INT32_TAS +#define HAS_TEST_AND_SET + +#define TAS(lock) tas(lock) + +typedef int slock_t; + +static __inline__ int +tas(volatile slock_t *lock) +{ + return __sync_lock_test_and_set(lock, 1); +} + +#define S_UNLOCK(lock) __sync_lock_release(lock) + +#endif /* HAVE_GCC__SYNC_INT32_TAS */ +#endif /* __arm__ || __arm || __aarch64__ || __aarch64 */ + + +/* + * RISC-V likewise uses __sync_lock_test_and_set(int *, int) if available. + */ +#if defined(__riscv) +#ifdef HAVE_GCC__SYNC_INT32_TAS +#define HAS_TEST_AND_SET + +#define TAS(lock) tas(lock) + +typedef int slock_t; + +static __inline__ int +tas(volatile slock_t *lock) +{ + return __sync_lock_test_and_set(lock, 1); +} + +#define S_UNLOCK(lock) __sync_lock_release(lock) + +#endif /* HAVE_GCC__SYNC_INT32_TAS */ +#endif /* __riscv */ + + +/* S/390 and S/390x Linux (32- and 64-bit zSeries) */ +#if defined(__s390__) || defined(__s390x__) +#define HAS_TEST_AND_SET + +typedef unsigned int slock_t; + +#define TAS(lock) tas(lock) + +static __inline__ int +tas(volatile slock_t *lock) +{ + int _res = 0; + + __asm__ __volatile__( + " cs %0,%3,0(%2) \n" +: "+d"(_res), "+m"(*lock) +: "a"(lock), "d"(1) +: "memory", "cc"); + return _res; +} + +#endif /* __s390__ || __s390x__ */ + + +#if defined(__sparc__) /* Sparc */ +/* + * Solaris has always run sparc processors in TSO (total store) mode, but + * linux didn't use to and the *BSDs still don't. So, be careful about + * acquire/release semantics. The CPU will treat superfluous membars as + * NOPs, so it's just code space. + */ +#define HAS_TEST_AND_SET + +typedef unsigned char slock_t; + +#define TAS(lock) tas(lock) + +static __inline__ int +tas(volatile slock_t *lock) +{ + register slock_t _res; + + /* + * See comment in src/backend/port/tas/sunstudio_sparc.s for why this + * uses "ldstub", and that file uses "cas". gcc currently generates + * sparcv7-targeted binaries, so "cas" use isn't possible. + */ + __asm__ __volatile__( + " ldstub [%2], %0 \n" +: "=r"(_res), "+m"(*lock) +: "r"(lock) +: "memory"); +#if defined(__sparcv7) || defined(__sparc_v7__) + /* + * No stbar or membar available, luckily no actually produced hardware + * requires a barrier. + */ +#elif defined(__sparcv8) || defined(__sparc_v8__) + /* stbar is available (and required for both PSO, RMO), membar isn't */ + __asm__ __volatile__ ("stbar \n":::"memory"); +#else + /* + * #LoadStore (RMO) | #LoadLoad (RMO) together are the appropriate acquire + * barrier for sparcv8+ upwards. + */ + __asm__ __volatile__ ("membar #LoadStore | #LoadLoad \n":::"memory"); +#endif + return (int) _res; +} + +#if defined(__sparcv7) || defined(__sparc_v7__) +/* + * No stbar or membar available, luckily no actually produced hardware + * requires a barrier. We fall through to the default gcc definition of + * S_UNLOCK in this case. + */ +#elif defined(__sparcv8) || defined(__sparc_v8__) +/* stbar is available (and required for both PSO, RMO), membar isn't */ +#define S_UNLOCK(lock) \ +do \ +{ \ + __asm__ __volatile__ ("stbar \n":::"memory"); \ + *((volatile slock_t *) (lock)) = 0; \ +} while (0) +#else +/* + * #LoadStore (RMO) | #StoreStore (RMO, PSO) together are the appropriate + * release barrier for sparcv8+ upwards. + */ +#define S_UNLOCK(lock) \ +do \ +{ \ + __asm__ __volatile__ ("membar #LoadStore | #StoreStore \n":::"memory"); \ + *((volatile slock_t *) (lock)) = 0; \ +} while (0) +#endif + +#endif /* __sparc__ */ + + +/* PowerPC */ +#if defined(__ppc__) || defined(__powerpc__) || defined(__ppc64__) || defined(__powerpc64__) +#define HAS_TEST_AND_SET + +typedef unsigned int slock_t; + +#define TAS(lock) tas(lock) + +/* On PPC, it's a win to use a non-locking test before the lwarx */ +#define TAS_SPIN(lock) (*(lock) ? 1 : TAS(lock)) + +/* + * The second operand of addi can hold a constant zero or a register number, + * hence constraint "=&b" to avoid allocating r0. "b" stands for "address + * base register"; most operands having this register-or-zero property are + * address bases, e.g. the second operand of lwax. + * + * NOTE: per the Enhanced PowerPC Architecture manual, v1.0 dated 7-May-2002, + * an isync is a sufficient synchronization barrier after a lwarx/stwcx loop. + * On newer machines, we can use lwsync instead for better performance. + * + * Ordinarily, we'd code the branches here using GNU-style local symbols, that + * is "1f" referencing "1:" and so on. But some people run gcc on AIX with + * IBM's assembler as backend, and IBM's assembler doesn't do local symbols. + * So hand-code the branch offsets; fortunately, all PPC instructions are + * exactly 4 bytes each, so it's not too hard to count. + */ +static __inline__ int +tas(volatile slock_t *lock) +{ + slock_t _t; + int _res; + + __asm__ __volatile__( +#ifdef USE_PPC_LWARX_MUTEX_HINT +" lwarx %0,0,%3,1 \n" +#else +" lwarx %0,0,%3 \n" +#endif +" cmpwi %0,0 \n" +" bne $+16 \n" /* branch to li %1,1 */ +" addi %0,%0,1 \n" +" stwcx. %0,0,%3 \n" +" beq $+12 \n" /* branch to lwsync/isync */ +" li %1,1 \n" +" b $+12 \n" /* branch to end of asm sequence */ +#ifdef USE_PPC_LWSYNC +" lwsync \n" +#else +" isync \n" +#endif +" li %1,0 \n" + +: "=&b"(_t), "=r"(_res), "+m"(*lock) +: "r"(lock) +: "memory", "cc"); + return _res; +} + +/* + * PowerPC S_UNLOCK is almost standard but requires a "sync" instruction. + * On newer machines, we can use lwsync instead for better performance. + */ +#ifdef USE_PPC_LWSYNC +#define S_UNLOCK(lock) \ +do \ +{ \ + __asm__ __volatile__ (" lwsync \n" ::: "memory"); \ + *((volatile slock_t *) (lock)) = 0; \ +} while (0) +#else +#define S_UNLOCK(lock) \ +do \ +{ \ + __asm__ __volatile__ (" sync \n" ::: "memory"); \ + *((volatile slock_t *) (lock)) = 0; \ +} while (0) +#endif /* USE_PPC_LWSYNC */ + +#endif /* powerpc */ + + +/* Linux Motorola 68k */ +#if (defined(__mc68000__) || defined(__m68k__)) && defined(__linux__) +#define HAS_TEST_AND_SET + +typedef unsigned char slock_t; + +#define TAS(lock) tas(lock) + +static __inline__ int +tas(volatile slock_t *lock) +{ + register int rv; + + __asm__ __volatile__( + " clrl %0 \n" + " tas %1 \n" + " sne %0 \n" +: "=d"(rv), "+m"(*lock) +: /* no inputs */ +: "memory", "cc"); + return rv; +} + +#endif /* (__mc68000__ || __m68k__) && __linux__ */ + + +/* Motorola 88k */ +#if defined(__m88k__) +#define HAS_TEST_AND_SET + +typedef unsigned int slock_t; + +#define TAS(lock) tas(lock) + +static __inline__ int +tas(volatile slock_t *lock) +{ + register slock_t _res = 1; + + __asm__ __volatile__( + " xmem %0, %2, %%r0 \n" +: "+r"(_res), "+m"(*lock) +: "r"(lock) +: "memory"); + return (int) _res; +} + +#endif /* __m88k__ */ + + +/* + * VAXen -- even multiprocessor ones + * (thanks to Tom Ivar Helbekkmo) + */ +#if defined(__vax__) +#define HAS_TEST_AND_SET + +typedef unsigned char slock_t; + +#define TAS(lock) tas(lock) + +static __inline__ int +tas(volatile slock_t *lock) +{ + register int _res; + + __asm__ __volatile__( + " movl $1, %0 \n" + " bbssi $0, (%2), 1f \n" + " clrl %0 \n" + "1: \n" +: "=&r"(_res), "+m"(*lock) +: "r"(lock) +: "memory"); + return _res; +} + +#endif /* __vax__ */ + + +#if defined(__mips__) && !defined(__sgi) /* non-SGI MIPS */ +#define HAS_TEST_AND_SET + +typedef unsigned int slock_t; + +#define TAS(lock) tas(lock) + +/* + * Original MIPS-I processors lacked the LL/SC instructions, but if we are + * so unfortunate as to be running on one of those, we expect that the kernel + * will handle the illegal-instruction traps and emulate them for us. On + * anything newer (and really, MIPS-I is extinct) LL/SC is the only sane + * choice because any other synchronization method must involve a kernel + * call. Unfortunately, many toolchains still default to MIPS-I as the + * codegen target; if the symbol __mips shows that that's the case, we + * have to force the assembler to accept LL/SC. + * + * R10000 and up processors require a separate SYNC, which has the same + * issues as LL/SC. + */ +#if __mips < 2 +#define MIPS_SET_MIPS2 " .set mips2 \n" +#else +#define MIPS_SET_MIPS2 +#endif + +static __inline__ int +tas(volatile slock_t *lock) +{ + register volatile slock_t *_l = lock; + register int _res; + register int _tmp; + + __asm__ __volatile__( + " .set push \n" + MIPS_SET_MIPS2 + " .set noreorder \n" + " .set nomacro \n" + " ll %0, %2 \n" + " or %1, %0, 1 \n" + " sc %1, %2 \n" + " xori %1, 1 \n" + " or %0, %0, %1 \n" + " sync \n" + " .set pop " +: "=&r" (_res), "=&r" (_tmp), "+R" (*_l) +: /* no inputs */ +: "memory"); + return _res; +} + +/* MIPS S_UNLOCK is almost standard but requires a "sync" instruction */ +#define S_UNLOCK(lock) \ +do \ +{ \ + __asm__ __volatile__( \ + " .set push \n" \ + MIPS_SET_MIPS2 \ + " .set noreorder \n" \ + " .set nomacro \n" \ + " sync \n" \ + " .set pop " \ +: /* no outputs */ \ +: /* no inputs */ \ +: "memory"); \ + *((volatile slock_t *) (lock)) = 0; \ +} while (0) + +#endif /* __mips__ && !__sgi */ + + +#if defined(__m32r__) && defined(HAVE_SYS_TAS_H) /* Renesas' M32R */ +#define HAS_TEST_AND_SET + +#include <sys/tas.h> + +typedef int slock_t; + +#define TAS(lock) tas(lock) + +#endif /* __m32r__ */ + + +#if defined(__sh__) /* Renesas' SuperH */ +#define HAS_TEST_AND_SET + +typedef unsigned char slock_t; + +#define TAS(lock) tas(lock) + +static __inline__ int +tas(volatile slock_t *lock) +{ + register int _res; + + /* + * This asm is coded as if %0 could be any register, but actually SuperH + * restricts the target of xor-immediate to be R0. That's handled by + * the "z" constraint on _res. + */ + __asm__ __volatile__( + " tas.b @%2 \n" + " movt %0 \n" + " xor #1,%0 \n" +: "=z"(_res), "+m"(*lock) +: "r"(lock) +: "memory", "t"); + return _res; +} + +#endif /* __sh__ */ + + +/* These live in s_lock.c, but only for gcc */ + + +#if defined(__m68k__) && !defined(__linux__) /* non-Linux Motorola 68k */ +#define HAS_TEST_AND_SET + +typedef unsigned char slock_t; +#endif + +/* + * Default implementation of S_UNLOCK() for gcc/icc. + * + * Note that this implementation is unsafe for any platform that can reorder + * a memory access (either load or store) after a following store. That + * happens not to be possible on x86 and most legacy architectures (some are + * single-processor!), but many modern systems have weaker memory ordering. + * Those that do must define their own version of S_UNLOCK() rather than + * relying on this one. + */ +#if !defined(S_UNLOCK) +#define S_UNLOCK(lock) \ + do { __asm__ __volatile__("" : : : "memory"); *(lock) = 0; } while (0) +#endif + +#endif /* defined(__GNUC__) || defined(__INTEL_COMPILER) */ + + + +/* + * --------------------------------------------------------------------- + * Platforms that use non-gcc inline assembly: + * --------------------------------------------------------------------- + */ + +#if !defined(HAS_TEST_AND_SET) /* We didn't trigger above, let's try here */ + + +#if defined(__hppa) || defined(__hppa__) /* HP PA-RISC, GCC and HP compilers */ +/* + * HP's PA-RISC + * + * See src/backend/port/hpux/tas.c.template for details about LDCWX. Because + * LDCWX requires a 16-byte-aligned address, we declare slock_t as a 16-byte + * struct. The active word in the struct is whichever has the aligned address; + * the other three words just sit at -1. + * + * When using gcc, we can inline the required assembly code. + */ +#define HAS_TEST_AND_SET + +typedef struct +{ + int sema[4]; +} slock_t; + +#define TAS_ACTIVE_WORD(lock) ((volatile int *) (((uintptr_t) (lock) + 15) & ~15)) + +#if defined(__GNUC__) + +static __inline__ int +tas(volatile slock_t *lock) +{ + volatile int *lockword = TAS_ACTIVE_WORD(lock); + register int lockval; + + __asm__ __volatile__( + " ldcwx 0(0,%2),%0 \n" +: "=r"(lockval), "+m"(*lockword) +: "r"(lockword) +: "memory"); + return (lockval == 0); +} + +/* + * The hppa implementation doesn't follow the rules of this files and provides + * a gcc specific implementation outside of the above defined(__GNUC__). It + * does so to avoid duplication between the HP compiler and gcc. So undefine + * the generic fallback S_UNLOCK from above. + */ +#ifdef S_UNLOCK +#undef S_UNLOCK +#endif +#define S_UNLOCK(lock) \ + do { \ + __asm__ __volatile__("" : : : "memory"); \ + *TAS_ACTIVE_WORD(lock) = -1; \ + } while (0) + +#endif /* __GNUC__ */ + +#define S_INIT_LOCK(lock) \ + do { \ + volatile slock_t *lock_ = (lock); \ + lock_->sema[0] = -1; \ + lock_->sema[1] = -1; \ + lock_->sema[2] = -1; \ + lock_->sema[3] = -1; \ + } while (0) + +#define S_LOCK_FREE(lock) (*TAS_ACTIVE_WORD(lock) != 0) + +#endif /* __hppa || __hppa__ */ + + +#if defined(__hpux) && defined(__ia64) && !defined(__GNUC__) +/* + * HP-UX on Itanium, non-gcc/icc compiler + * + * We assume that the compiler enforces strict ordering of loads/stores on + * volatile data (see comments on the gcc-version earlier in this file). + * Note that this assumption does *not* hold if you use the + * +Ovolatile=__unordered option on the HP-UX compiler, so don't do that. + * + * See also Implementing Spinlocks on the Intel Itanium Architecture and + * PA-RISC, by Tor Ekqvist and David Graves, for more information. As of + * this writing, version 1.0 of the manual is available at: + * http://h21007.www2.hp.com/portal/download/files/unprot/itanium/spinlocks.pdf + */ +#define HAS_TEST_AND_SET + +typedef unsigned int slock_t; + +#include <ia64/sys/inline.h> +#define TAS(lock) _Asm_xchg(_SZ_W, lock, 1, _LDHINT_NONE) +/* On IA64, it's a win to use a non-locking test before the xchg proper */ +#define TAS_SPIN(lock) (*(lock) ? 1 : TAS(lock)) +#define S_UNLOCK(lock) \ + do { _Asm_mf(); (*(lock)) = 0; } while (0) + +#endif /* HPUX on IA64, non gcc/icc */ + +#if defined(_AIX) /* AIX */ +/* + * AIX (POWER) + */ +#define HAS_TEST_AND_SET + +#include <sys/atomic_op.h> + +typedef int slock_t; + +#define TAS(lock) _check_lock((slock_t *) (lock), 0, 1) +#define S_UNLOCK(lock) _clear_lock((slock_t *) (lock), 0) +#endif /* _AIX */ + + +/* These are in sunstudio_(sparc|x86).s */ + +#if defined(__SUNPRO_C) && (defined(__i386) || defined(__x86_64__) || defined(__sparc__) || defined(__sparc)) +#define HAS_TEST_AND_SET + +#if defined(__i386) || defined(__x86_64__) || defined(__sparcv9) || defined(__sparcv8plus) +typedef unsigned int slock_t; +#else +typedef unsigned char slock_t; +#endif + +extern slock_t pg_atomic_cas(volatile slock_t *lock, slock_t with, + slock_t cmp); + +#define TAS(a) (pg_atomic_cas((a), 1, 0) != 0) +#endif + + +#ifdef _MSC_VER +typedef LONG slock_t; + +#define HAS_TEST_AND_SET +#define TAS(lock) (InterlockedCompareExchange(lock, 1, 0)) + +#define SPIN_DELAY() spin_delay() + +/* If using Visual C++ on Win64, inline assembly is unavailable. + * Use a _mm_pause intrinsic instead of rep nop. + */ +#if defined(_WIN64) +static __forceinline void +spin_delay(void) +{ + _mm_pause(); +} +#else +static __forceinline void +spin_delay(void) +{ + /* See comment for gcc code. Same code, MASM syntax */ + __asm rep nop; +} +#endif + +#include <intrin.h> +#pragma intrinsic(_ReadWriteBarrier) + +#define S_UNLOCK(lock) \ + do { _ReadWriteBarrier(); (*(lock)) = 0; } while (0) + +#endif + + +#endif /* !defined(HAS_TEST_AND_SET) */ + + +/* Blow up if we didn't have any way to do spinlocks */ +#ifndef HAS_TEST_AND_SET +#error PostgreSQL does not have native spinlock support on this platform. To continue the compilation, rerun configure using --disable-spinlocks. However, performance will be poor. Please report this to pgsql-bugs@lists.postgresql.org. +#endif + + +#else /* !HAVE_SPINLOCKS */ + + +/* + * Fake spinlock implementation using semaphores --- slow and prone + * to fall foul of kernel limits on number of semaphores, so don't use this + * unless you must! The subroutines appear in spin.c. + */ +typedef int slock_t; + +extern bool s_lock_free_sema(volatile slock_t *lock); +extern void s_unlock_sema(volatile slock_t *lock); +extern void s_init_lock_sema(volatile slock_t *lock, bool nested); +extern int tas_sema(volatile slock_t *lock); + +#define S_LOCK_FREE(lock) s_lock_free_sema(lock) +#define S_UNLOCK(lock) s_unlock_sema(lock) +#define S_INIT_LOCK(lock) s_init_lock_sema(lock, false) +#define TAS(lock) tas_sema(lock) + + +#endif /* HAVE_SPINLOCKS */ + + +/* + * Default Definitions - override these above as needed. + */ + +#if !defined(S_LOCK) +#define S_LOCK(lock) \ + (TAS(lock) ? s_lock((lock), __FILE__, __LINE__, PG_FUNCNAME_MACRO) : 0) +#endif /* S_LOCK */ + +#if !defined(S_LOCK_FREE) +#define S_LOCK_FREE(lock) (*(lock) == 0) +#endif /* S_LOCK_FREE */ + +#if !defined(S_UNLOCK) +/* + * Our default implementation of S_UNLOCK is essentially *(lock) = 0. This + * is unsafe if the platform can reorder a memory access (either load or + * store) after a following store; platforms where this is possible must + * define their own S_UNLOCK. But CPU reordering is not the only concern: + * if we simply defined S_UNLOCK() as an inline macro, the compiler might + * reorder instructions from inside the critical section to occur after the + * lock release. Since the compiler probably can't know what the external + * function s_unlock is doing, putting the same logic there should be adequate. + * A sufficiently-smart globally optimizing compiler could break that + * assumption, though, and the cost of a function call for every spinlock + * release may hurt performance significantly, so we use this implementation + * only for platforms where we don't know of a suitable intrinsic. For the + * most part, those are relatively obscure platform/compiler combinations to + * which the PostgreSQL project does not have access. + */ +#define USE_DEFAULT_S_UNLOCK +extern void s_unlock(volatile slock_t *lock); +#define S_UNLOCK(lock) s_unlock(lock) +#endif /* S_UNLOCK */ + +#if !defined(S_INIT_LOCK) +#define S_INIT_LOCK(lock) S_UNLOCK(lock) +#endif /* S_INIT_LOCK */ + +#if !defined(SPIN_DELAY) +#define SPIN_DELAY() ((void) 0) +#endif /* SPIN_DELAY */ + +#if !defined(TAS) +extern int tas(volatile slock_t *lock); /* in port/.../tas.s, or + * s_lock.c */ + +#define TAS(lock) tas(lock) +#endif /* TAS */ + +#if !defined(TAS_SPIN) +#define TAS_SPIN(lock) TAS(lock) +#endif /* TAS_SPIN */ + +extern slock_t dummy_spinlock; + +/* + * Platform-independent out-of-line support routines + */ +extern int s_lock(volatile slock_t *lock, const char *file, int line, const char *func); + +/* Support for dynamic adjustment of spins_per_delay */ +#define DEFAULT_SPINS_PER_DELAY 100 + +extern void set_spins_per_delay(int shared_spins_per_delay); +extern int update_spins_per_delay(int shared_spins_per_delay); + +/* + * Support for spin delay which is useful in various places where + * spinlock-like procedures take place. + */ +typedef struct +{ + int spins; + int delays; + int cur_delay; + const char *file; + int line; + const char *func; +} SpinDelayStatus; + +static inline void +init_spin_delay(SpinDelayStatus *status, + const char *file, int line, const char *func) +{ + status->spins = 0; + status->delays = 0; + status->cur_delay = 0; + status->file = file; + status->line = line; + status->func = func; +} + +#define init_local_spin_delay(status) init_spin_delay(status, __FILE__, __LINE__, PG_FUNCNAME_MACRO) +void perform_spin_delay(SpinDelayStatus *status); +void finish_spin_delay(SpinDelayStatus *status); + +#endif /* S_LOCK_H */ |