Add dbLinkDoLocked() support

New lset method, implemented in all link types.
Includes a test for the dbCa implementation.

src/ioc/db/dbCa.c

@@ -684,6 +684,17 @@ static long getUnits(const struct link *plink,
     return gotAttributes ? 0 : -1;
 }
 
+static long doLocked(struct link *plink, dbLinkUserCallback rtn, void *priv)
+{
+    caLink *pca;
+    long status;
+
+    pcaGetCheck
+    status = rtn(plink, priv);
+    epicsMutexUnlock(pca->lock);
+    return status;
+}
+
 static void scanComplete(void *raw, dbCommon *prec)
 {
     caLink *pca = raw;
@@ -727,7 +738,7 @@ static lset dbCa_lset = {
     getPrecision, getUnits,
     getAlarm, getTimeStamp,
     dbCaPutLink, dbCaPutAsync,
-    scanForward
+    scanForward, doLocked
 };
 
 static void connectionCallback(struct connection_handler_args arg)

src/ioc/db/dbConstLink.c

@@ -135,6 +135,5 @@ static lset dbConst_lset = {
     NULL, NULL,
     NULL, NULL,
     NULL, NULL,
-    NULL
+    NULL, NULL
 };
-

src/ioc/db/dbDbLink.c

@@ -337,6 +337,11 @@ static void dbDbScanFwdLink(struct link *plink)
     dbScanPassive(precord, paddr->precord);
 }
 
+static long doLocked(struct link *plink, dbLinkUserCallback rtn, void *priv)
+{
+    return rtn(plink, priv);
+}
+
 static lset dbDb_lset = {
     0, 0, /* not Constant, not Volatile */
     NULL, dbDbRemoveLink,
@@ -348,6 +353,5 @@ static lset dbDb_lset = {
     dbDbGetPrecision, dbDbGetUnits,
     dbDbGetAlarm, dbDbGetTimeStamp,
     dbDbPutValue, NULL,
-    dbDbScanFwdLink
+    dbDbScanFwdLink, doLocked
 };
-

src/ioc/db/dbLink.c

@@ -414,6 +414,18 @@ void dbScanFwdLink(struct link *plink)
         plset->scanForward(plink);
 }
 
+long dbLinkDoLocked(struct link *plink, dbLinkUserCallback rtn,
+        void *priv)
+{
+    lset *plset = plink->lset;
+
+    if (!rtn || !plset || !plset->doLocked)
+        return S_db_noLSET;
+
+    return plset->doLocked(plink, rtn, priv);
+}
+
+
 /* Helper functions for long string support */
 
 long dbGetLinkLS(struct link *plink, char *pbuffer, epicsUInt32 size,

src/ioc/db/dbLink.h

@@ -27,6 +27,8 @@ extern "C" {
 
 struct dbLocker;
 
+typedef long (*dbLinkUserCallback)(struct link *plink, void *priv);
+
 typedef struct lset {
     /* Characteristics of the link type */
     const unsigned isConstant:1;
@@ -71,6 +73,9 @@ typedef struct lset {
 
     /* Process */
     void (*scanForward)(struct link *plink);
+
+    /* Atomicity */
+    long (*doLocked)(struct link *plink, dbLinkUserCallback rtn, void *priv);
 } lset;
 
 #define dbGetSevr(link, sevr) \
@@ -117,6 +122,9 @@ epicsShareFunc long dbPutLinkAsync(struct link *plink, short dbrType,
         const void *pbuffer, long nRequest);
 epicsShareFunc void dbScanFwdLink(struct link *plink);
 
+epicsShareFunc long dbLinkDoLocked(struct link *plink, dbLinkUserCallback rtn,
+        void *priv);
+
 epicsShareFunc long dbLoadLinkLS(struct link *plink, char *pbuffer,
         epicsUInt32 size, epicsUInt32 *plen);
 epicsShareFunc long dbGetLinkLS(struct link *plink, char *pbuffer,

src/ioc/db/test/dbCaLinkTest.c

@@ -107,6 +107,39 @@ void putLink(DBLINK *plink, short dbr, const void*buf, long nReq)
     waitEvent = NULL;
 }
 
+static long getTwice(struct link *psrclnk, void *dummy)
+{
+    epicsInt32 val1, val2;
+    long status = dbGetLink(psrclnk, DBR_LONG, &val1, 0, 0);
+
+    if (status) return status;
+
+    epicsThreadSleep(0.5);
+    status = dbGetLink(psrclnk, DBR_LONG, &val2, 0, 0);
+    if (status) return status;
+
+    testDiag("val1 = %d, val2 = %d", val1, val2);
+    return (val1 == val2) ? 0 : -1;
+}
+
+static void countUp(void *parm)
+{
+    xRecord *ptarg = (xRecord *)parm;
+    epicsInt32 val;
+
+    for (val = 1; val < 10; val++) {
+        dbScanLock((dbCommon*)ptarg);
+        ptarg->val = val;
+        db_post_events(ptarg, &ptarg->val, DBE_VALUE|DBE_ALARM|DBE_ARCHIVE);
+        dbScanUnlock((dbCommon*)ptarg);
+
+        epicsThreadSleep(0.1);
+    }
+
+    if (waitEvent)
+        epicsEventMustTrigger(waitEvent);
+}
+
 static void testNativeLink(void)
 {
     xRecord *psrc, *ptarg;
@@ -166,6 +199,27 @@ static void testNativeLink(void)
     testOk1(ptarg->val==1010);
     dbScanUnlock((dbCommon*)ptarg);
 
+    assert(!waitEvent);
+    waitEvent = epicsEventMustCreate(epicsEventEmpty);
+
+    /* Start counter */
+    epicsThreadCreate("countUp", epicsThreadPriorityHigh,
+        epicsThreadGetStackSize(epicsThreadStackSmall), countUp, ptarg);
+
+    dbScanLock((dbCommon*)psrc);
+    /* Check that unlocked gets change */
+    temp = getTwice(psrclnk, NULL);
+    testOk(temp == -1, "unlocked, getTwice returned %d (-1)", temp);
+
+    /* Check locked gets are atomic */
+    temp = dbLinkDoLocked(psrclnk, getTwice, NULL);
+    testOk(temp == 0, "locked, getTwice returned %d (0)", temp);
+    dbScanUnlock((dbCommon*)psrc);
+
+    epicsEventMustWait(waitEvent);
+    epicsEventDestroy(waitEvent);
+    waitEvent = NULL;
+
     testIocShutdownOk();
 
     testdbCleanup();
@@ -598,7 +652,7 @@ static void testCAC(void)
 
 MAIN(dbCaLinkTest)
 {
-    testPlan(99);
+    testPlan(101);
     testNativeLink();
     testStringLink();
     testCP();

src/ioc/db/test/jlinkz.c

@@ -146,6 +146,7 @@ static lset lsetZ = {
     &z_putval,
     NULL, /* putasync */
     NULL, /* forward */
+    NULL, /* doLocked */
 };
 
 static

src/ioc/db/test/xLink.c

@@ -73,7 +73,7 @@ static lset xlink_lset = {
     NULL, NULL,
     NULL, NULL,
     NULL, NULL,
-    NULL
+    NULL, NULL
 };
 
 static jlif xlinkIf = {

src/std/link/lnkCalc.c

@@ -597,6 +597,11 @@ static long lnkCalc_getAlarm(const struct link *plink, epicsEnum16 *status,
     return 0;
 }
 
+static long doLocked(struct link *plink, dbLinkUserCallback rtn, void *priv)
+{
+    return rtn(plink, priv);
+}
+
 
 /************************* Interface Tables *************************/
 
@@ -610,7 +615,7 @@ static lset lnkCalc_lset = {
     lnkCalc_getPrecision, lnkCalc_getUnits,
     lnkCalc_getAlarm, NULL,
     NULL, NULL,
-    NULL
+    NULL, doLocked
 };
 
 static jlif lnkCalcIf = {

src/std/link/lnkConst.c

@@ -551,7 +551,7 @@ static lset lnkConst_lset = {
     NULL, NULL,
     NULL, NULL,
     NULL, NULL,
-    NULL
+    NULL, NULL
 };
 
 static jlif lnkConstIf = {