Merge in changes to avoid a few potential problems with LLUUID when accessed from multiple threads.

indra/llcommon/lluuid.cpp

@@ -41,10 +41,15 @@
 #include "llmd5.h"
 #include "llstring.h"
 #include "lltimer.h"
+#include "llthread.h"
 
 const LLUUID LLUUID::null;
 const LLTransactionID LLTransactionID::tnull;
 
+// static 
+LLMutex * LLUUID::mMutex = NULL;
+
+
 /*
 
 NOT DONE YET!!!
@@ -731,6 +736,7 @@ void LLUUID::getCurrentTime(uuid_time_t *timestamp)
       getSystemTime(&time_last);
       uuids_this_tick = uuids_per_tick;
       init = TRUE;
+	  mMutex = new LLMutex;
    }
 
    uuid_time_t time_now = {0,0};
@@ -782,6 +788,7 @@ void LLUUID::generate()
 #endif
 	if (!has_init) 
 	{
+		has_init = 1;
 		if (getNodeID(node_id) <= 0) 
 		{
 			get_random_bytes(node_id, 6);
@@ -803,18 +810,24 @@ void LLUUID::generate()
 #else
 		clock_seq = (U16)ll_rand(65536);
 #endif
-		has_init = 1;
 	}
 
 	// get current time
 	getCurrentTime(&timestamp);
+	U16 our_clock_seq = clock_seq;
 
-	// if clock went backward change clockseq
-	if (cmpTime(&timestamp, &time_last) == -1) {
+	// if clock hasn't changed or went backward, change clockseq
+	if (cmpTime(&timestamp, &time_last) != 1) 
+	{
+		LLMutexLock	lock(mMutex);
 		clock_seq = (clock_seq + 1) & 0x3FFF;
-		if (clock_seq == 0) clock_seq++;
+		if (clock_seq == 0) 
+			clock_seq++;
+		our_clock_seq = clock_seq;	// Ensure we're using a different clock_seq value from previous time
 	}
 
+    time_last = timestamp;
+
 	memcpy(mData+10, node_id, 6);		/* Flawfinder: ignore */
 	U32 tmp;
 	tmp = timestamp.low;
@@ -836,7 +849,8 @@ void LLUUID::generate()
 	tmp >>= 8;
 	mData[6] = (unsigned char) tmp;
 
-	tmp = clock_seq;
+	tmp = our_clock_seq;
+
 	mData[9] = (unsigned char) tmp;
 	tmp >>= 8;
 	mData[8] = (unsigned char) tmp;
@@ -846,8 +860,6 @@ void LLUUID::generate()
 	md5_uuid.update(mData,16);
 	md5_uuid.finalize();
 	md5_uuid.raw_digest(mData);
-
-    time_last = timestamp;
 }
 
 void LLUUID::generate(const std::string& hash_string)
@@ -861,8 +873,14 @@ U32 LLUUID::getRandomSeed()
    static unsigned char seed[16];		/* Flawfinder: ignore */
    
    getNodeID(&seed[0]);
-   seed[6]='\0';
-   seed[7]='\0';
+
+   // Incorporate the pid into the seed to prevent
+   // processes that start on the same host at the same
+   // time from generating the same seed.
+   pid_t pid = LLApp::getPid();
+
+   seed[6]=(unsigned char)(pid >> 8);
+   seed[7]=(unsigned char)(pid);
    getSystemTime((uuid_time_t *)(&seed[8]));
 
    LLMD5 md5_seed;

indra/llcommon/lluuid.h

@@ -31,6 +31,8 @@
 #include "stdtypes.h"
 #include "llpreprocessor.h"
 
+class LLMutex;
+
 const S32 UUID_BYTES = 16;
 const S32 UUID_WORDS = 4;
 const S32 UUID_STR_LENGTH = 37;	// actually wrong, should be 36 and use size below
@@ -118,6 +120,7 @@ public:
 	static BOOL validate(const std::string& in_string); // Validate that the UUID string is legal.
 
 	static const LLUUID null;
+	static LLMutex * mMutex;
 
 	static U32 getRandomSeed();
 	static S32 getNodeID(unsigned char * node_id);