diff options
| -rw-r--r-- | indra/llcommon/llrand.cpp | 20 |
1 files changed, 18 insertions, 2 deletions
diff --git a/indra/llcommon/llrand.cpp b/indra/llcommon/llrand.cpp index 33afc50cf7..20e25177f0 100644 --- a/indra/llcommon/llrand.cpp +++ b/indra/llcommon/llrand.cpp @@ -28,6 +28,7 @@ #include "llrand.h" #include "lluuid.h" +#include "mutex.h" /** * Through analysis, we have decided that we want to take values which @@ -58,8 +59,17 @@ * to restore uniform distribution. */ +static std::mutex gRandomGeneratorMutex; static LLRandLagFib2281 gRandomGenerator(LLUUID::getRandomSeed()); +inline F64 ll_internal_random_unclamped() +{ + // gRandomGenerator is a stateful static object, which is therefore not + // inherently thread-safe. Lock it before use. + std::unique_lock lk(gRandomGeneratorMutex); + return gRandomGenerator(); +} + // no default implementation, only specific F64 and F32 specializations template <typename REAL> inline REAL ll_internal_random(); @@ -71,7 +81,7 @@ inline F64 ll_internal_random<F64>() // CPUs (or at least multi-threaded processes) seem to // occasionally give an obviously incorrect random number -- like // 5^15 or something. Sooooo, clamp it as described above. - F64 rv = gRandomGenerator(); + F64 rv{ ll_internal_random_unclamped() }; if(!((rv >= 0.0) && (rv < 1.0))) return fmod(rv, 1.0); return rv; } @@ -79,7 +89,13 @@ inline F64 ll_internal_random<F64>() template <> inline F32 ll_internal_random<F32>() { - return F32(ll_internal_random<F64>()); + // *HACK: clamp the result as described above. + // Per Monty, it's important to clamp using the correct fmodf() rather + // than expanding to F64 for fmod() and then truncating back to F32. Prior + // to this change, we were getting sporadic ll_frand() == 1.0 results. + F32 rv{ ll_internal_random_unclamped() }; + if(!((rv >= 0.0) && (rv < 1.0))) return fmodf(rv, 1.0f); + return rv; } /*------------------------------ F64 aliases -------------------------------*/ |