diff options
Diffstat (limited to 'src/backend')
| -rw-r--r-- | src/backend/postmaster/postmaster.c | 33 |
1 files changed, 25 insertions, 8 deletions
diff --git a/src/backend/postmaster/postmaster.c b/src/backend/postmaster/postmaster.c index eedc617db4c..2d5a0ac7d3b 100644 --- a/src/backend/postmaster/postmaster.c +++ b/src/backend/postmaster/postmaster.c @@ -2520,11 +2520,13 @@ ClosePostmasterPorts(bool am_syslogger) /* * InitProcessGlobals -- set MyProcPid, MyStartTime[stamp], random seeds * - * Called early in every backend. + * Called early in the postmaster and every backend. */ void InitProcessGlobals(void) { + unsigned int rseed; + MyProcPid = getpid(); MyStartTimestamp = GetCurrentTimestamp(); MyStartTime = timestamptz_to_time_t(MyStartTimestamp); @@ -2539,15 +2541,30 @@ InitProcessGlobals(void) #endif /* - * Set a different seed for random() in every backend. Since PIDs and - * timestamps tend to change more frequently in their least significant - * bits, shift the timestamp left to allow a larger total number of seeds - * in a given time period. Since that would leave only 20 bits of the - * timestamp that cycle every ~1 second, also mix in some higher bits. + * Set a different seed for random() in every process. We want something + * unpredictable, so if possible, use high-quality random bits for the + * seed. Otherwise, fall back to a seed based on timestamp and PID. + * + * Note we can't use pg_backend_random here, since this is used in the + * postmaster, and even in a backend we might not be attached to shared + * memory yet. */ - srandom(((uint64) MyProcPid) ^ +#ifdef HAVE_STRONG_RANDOM + if (!pg_strong_random(&rseed, sizeof(rseed))) +#endif + { + /* + * Since PIDs and timestamps tend to change more frequently in their + * least significant bits, shift the timestamp left to allow a larger + * total number of seeds in a given time period. Since that would + * leave only 20 bits of the timestamp that cycle every ~1 second, + * also mix in some higher bits. + */ + rseed = ((uint64) MyProcPid) ^ ((uint64) MyStartTimestamp << 12) ^ - ((uint64) MyStartTimestamp >> 20)); + ((uint64) MyStartTimestamp >> 20); + } + srandom(rseed); } |