diff options
author | dim <dim@FreeBSD.org> | 2015-01-31 23:48:59 +0000 |
---|---|---|
committer | dim <dim@FreeBSD.org> | 2015-01-31 23:48:59 +0000 |
commit | d55f158aa0c66ce046b7c35cebe1650e14161ca3 (patch) | |
tree | 6fd4f9ea15c58bd8ca9a6b8a85fdc9a5eb6ff31f /contrib/libcxxrt/guard.cc | |
parent | c6bc15d7ab08f753864c67985cc70c180d9cf799 (diff) | |
download | FreeBSD-src-d55f158aa0c66ce046b7c35cebe1650e14161ca3.zip FreeBSD-src-d55f158aa0c66ce046b7c35cebe1650e14161ca3.tar.gz |
MFC r273381 (by bapt):
Add support for __cxa_throw_bad_array_new_length in libcxxrt
It is required for use with newer g++49
Differential Revision: https://reviews.freebsd.org/D982
Reviewed by: theraven
Approved by: theraven
MFC r276417:
Import libcxxrt master 00bc29eb6513624824a6d7db2ebc768a4216a604.
Interesting fixes:
76584a0 Reorganize code to use only 32bit atomic ops for 32bit platforms
30d2ae5 Implement __cxa_throw_bad_array_new_length
Reviewed by: bapt
Differential Revision: https://reviews.freebsd.org/D1390
Diffstat (limited to 'contrib/libcxxrt/guard.cc')
-rw-r--r-- | contrib/libcxxrt/guard.cc | 105 |
1 files changed, 73 insertions, 32 deletions
diff --git a/contrib/libcxxrt/guard.cc b/contrib/libcxxrt/guard.cc index f0c26ab..f1c4c69 100644 --- a/contrib/libcxxrt/guard.cc +++ b/contrib/libcxxrt/guard.cc @@ -70,18 +70,45 @@ #ifdef __arm__ // ARM ABI - 32-bit guards. typedef uint32_t guard_t; -static const uint32_t LOCKED = ((guard_t)1) << 31; +typedef uint32_t guard_lock_t; +static const uint32_t LOCKED = static_cast<guard_t>(1) << 31; static const uint32_t INITIALISED = 1; -#else +#define LOCK_PART(guard) (guard) +#define INIT_PART(guard) (guard) +#elif defined(_LP64) typedef uint64_t guard_t; +typedef uint64_t guard_lock_t; # if defined(__LITTLE_ENDIAN__) -static const guard_t LOCKED = ((guard_t)1) << 63; +static const guard_t LOCKED = static_cast<guard_t>(1) << 63; static const guard_t INITIALISED = 1; # else static const guard_t LOCKED = 1; -static const guard_t INITIALISED = ((guard_t)1) << 56; +static const guard_t INITIALISED = static_cast<guard_t>(1) << 56; +# endif +#define LOCK_PART(guard) (guard) +#define INIT_PART(guard) (guard) +#else +typedef uint32_t guard_lock_t; +# if defined(__LITTLE_ENDIAN__) +typedef struct { + uint32_t init_half; + uint32_t lock_half; +} guard_t; +static const uint32_t LOCKED = static_cast<guard_lock_t>(1) << 31; +static const uint32_t INITIALISED = 1; +# else +typedef struct { + uint32_t init_half; + uint32_t lock_half; +} guard_t; +_Static_assert(sizeof(guard_t) == sizeof(uint64_t), ""); +static const uint32_t LOCKED = 1; +static const uint32_t INITIALISED = static_cast<guard_lock_t>(1) << 24; # endif +#define LOCK_PART(guard) (&(guard)->lock_half) +#define INIT_PART(guard) (&(guard)->init_half) #endif +static const guard_lock_t INITIAL = 0; /** * Acquires a lock on a guard, returning 0 if the object has already been @@ -90,42 +117,49 @@ static const guard_t INITIALISED = ((guard_t)1) << 56; */ extern "C" int __cxa_guard_acquire(volatile guard_t *guard_object) { + guard_lock_t old; // Not an atomic read, doesn't establish a happens-before relationship, but // if one is already established and we end up seeing an initialised state // then it's a fast path, otherwise we'll do something more expensive than // this test anyway... - if ((INITIALISED == *guard_object)) { return 0; } + if (INITIALISED == *INIT_PART(guard_object)) + return 0; // Spin trying to do the initialisation - while (1) + for (;;) { // Loop trying to move the value of the guard from 0 (not // locked, not initialised) to the locked-uninitialised // position. - switch (__sync_val_compare_and_swap(guard_object, 0, LOCKED)) - { - // If the old value was 0, we succeeded, so continue - // initialising - case 0: + old = __sync_val_compare_and_swap(LOCK_PART(guard_object), + INITIAL, LOCKED); + if (old == INITIAL) { + // Lock obtained. If lock and init bit are + // in separate words, check for init race. + if (INIT_PART(guard_object) == LOCK_PART(guard_object)) return 1; - // If this was already initialised, return and let the caller skip - // initialising it again. - case INITIALISED: - return 0; - // If it is locked by another thread, relinquish the CPU and try - // again later. - case LOCKED: - case LOCKED | INITIALISED: - sched_yield(); - break; - // If it is some other value, then something has gone badly wrong. - // Give up. - default: - fprintf(stderr, "Invalid state detected attempting to lock static initialiser.\n"); - abort(); + if (INITIALISED != *INIT_PART(guard_object)) + return 1; + + // No need for a memory barrier here, + // see first comment. + *LOCK_PART(guard_object) = INITIAL; + return 0; } + // If lock and init bit are in the same word, check again + // if we are done. + if (INIT_PART(guard_object) == LOCK_PART(guard_object) && + old == INITIALISED) + return 0; + + assert(old == LOCKED); + // Another thread holds the lock. + // If lock and init bit are in different words, check + // if we are done before yielding and looping. + if (INIT_PART(guard_object) != LOCK_PART(guard_object) && + INITIALISED == *INIT_PART(guard_object)) + return 0; + sched_yield(); } - //__builtin_unreachable(); - return 0; } /** @@ -135,7 +169,8 @@ extern "C" int __cxa_guard_acquire(volatile guard_t *guard_object) extern "C" void __cxa_guard_abort(volatile guard_t *guard_object) { __attribute__((unused)) - bool reset = __sync_bool_compare_and_swap(guard_object, LOCKED, 0); + bool reset = __sync_bool_compare_and_swap(LOCK_PART(guard_object), + LOCKED, INITIAL); assert(reset); } /** @@ -144,9 +179,15 @@ extern "C" void __cxa_guard_abort(volatile guard_t *guard_object) */ extern "C" void __cxa_guard_release(volatile guard_t *guard_object) { + guard_lock_t old; + if (INIT_PART(guard_object) == LOCK_PART(guard_object)) + old = LOCKED; + else + old = INITIAL; __attribute__((unused)) - bool reset = __sync_bool_compare_and_swap(guard_object, LOCKED, INITIALISED); + bool reset = __sync_bool_compare_and_swap(INIT_PART(guard_object), + old, INITIALISED); assert(reset); + if (INIT_PART(guard_object) != LOCK_PART(guard_object)) + *LOCK_PART(guard_object) = INITIAL; } - - |