Experimental Physics and
Industrial Control System

Dirk Zimoch via Core-talk <core-talk at aps.anl.gov> · Thu, 17 Jun 2021 19:50:15 -0000

diff --git a/modules/database/src/ioc/db/callback.c b/modules/database/src/ioc/db/callback.c
index 3fa2493..4a26e27 100644

--- a/modules/database/src/ioc/db/callback.c
+++ b/modules/database/src/ioc/db/callback.c
@@ -263,7 +263,9 @@ void callbackCleanup(void)
 
         assert(epicsAtomicGetIntT(&mySet->threadsRunning)==0);
         epicsEventDestroy(mySet->semWakeUp);
+        mySet->semWakeUp = NULL;
         epicsRingPointerDelete(mySet->queue);
+        mySet->queue = NULL;
     }
 
     epicsTimerQueueRelease(timerQueue);
@@ -333,6 +335,10 @@ int callbackRequest(epicsCallback *pcallback)
         return S_db_badChoice;
     }
     mySet = &callbackQueue[priority];
+    if (!mySet->queue) {
+        epicsInterruptContextMessage("callbackRequest: Callbacks not initialized\n");
+        return S_db_notInit;
+    }
     if (mySet->queueOverflow) return S_db_bufFull;
 
     pushOK = epicsRingPointerPush(mySet->queue, pcallback);

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https://bugs.launchpad.net/bugs/1932120

Title:
  callbackRequest potentially accesses uninitialized memory

Status in EPICS Base:
  New

Bug description:
  If epicsAtomicCmpAndSwapIntT() in callbackInit() fails for some reason
  (e.g. because of bug #1932118), the callback queues never get
  initialized (and callback threads never get started) and the following
  warning is printed during iocInit:

  Warning: callbackInit called again before callbackCleanup

  Nevertheless,  callbackRequest() will use these uninitialized queues
  (and an uninitialized event semaphore) without checking, resulting in
  strange message from a spinLock in the uninitialized queue:

  0x132f380 (timerQueue): epicsSpinLock(0x1fda0b79): Deadlock.
  Recursive lock, missed unlock or block when locked.Thread timerQueue (0x132f380) can't proceed, suspending.

  A patch is attached.

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Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System