Changeset 33166 in vbox

Timestamp:

Oct 15, 2010 6:09:39 PM (14 years ago)

Author:

vboxsync

Message:

semeventwait-r0drv-solaris.h: addressed a potential timeout race.

File:

• trunk/src/VBox/Runtime/r0drv/solaris/semeventwait-r0drv-solaris.h (modified) (7 diffs)

trunk/src/VBox/Runtime/r0drv/solaris/semeventwait-r0drv-solaris.h

@@ -72 +72 @@
     /** Cylic timer ID (used by the timeout callback). */
     cyclic_id_t     idCy;
+    /** The mutex associated with the condition variable wait. */
+    void volatile  *pvMtx;
 } RTR0SEMSOLWAIT;
 /** Pointer to a solaris semaphore wait structure.  */
@@ -160 +162 @@
     pWait->fInterruptible   = !!(fFlags & RTSEMWAIT_FLAGS_INTERRUPTIBLE);
     pWait->pThread          = curthread;
+    pWait->pvMtx            = NULL;
     pWait->idCy             = CYCLIC_NONE;
 
@@ -176 +179 @@
     PRTR0SEMSOLWAIT pWait   = (PRTR0SEMSOLWAIT)pvUser;
     kthread_t      *pThread = pWait->pThread;
-    if (VALID_PTR(pThread)) /* paranoia */
-    {
-        /* Note: Trying to take the cpu_lock here doesn't work. */
+    kmutex_t       *pMtx    = (kmutex_t *)ASMAtomicReadPtr(&pWait->pvMtx);
+    if (VALID_PTR(pMtx))
+    {
+        /* Enter the mutex here to make sure the thread has gone to sleep
+           before we wake it up.
+           Note: Trying to take the cpu_lock here doesn't work. */
+        mutex_enter(pMtx);
         if (mutex_owner(&cpu_lock) == curthread)
         {
@@ -185 +192 @@
         }
         ASMAtomicWriteBool(&pWait->fTimedOut, true);
+        mutex_exit(pMtx);
         setrun(pThread);
     }
@@ -200 +208 @@
     PRTR0SEMSOLWAIT pWait   = (PRTR0SEMSOLWAIT)pvUser;
     kthread_t      *pThread = pWait->pThread;
-    if (VALID_PTR(pThread)) /* paranoia */
-    {
+    kmutex_t       *pMtx    = (kmutex_t *)ASMAtomicReadPtr(&pWait->pvMtx);
+    if (VALID_PTR(pMtx))
+    {
+        /* Enter the mutex here to make sure the thread has gone to sleep
+           before we wake it up. */
+        mutex_enter(pMtx);
         ASMAtomicWriteBool(&pWait->fTimedOut, true);
+        mutex_exit(pMtx);
         setrun(pThread);
     }
@@ -230 +243 @@
     if (fHasTimeout)
     {
+        ASMAtomicWritePtr(&pWait->pvMtx, pMtx); /* atomic is paranoia */
+
         if (pWait->fHighRes)
         {
@@ -294 +309 @@
     /*
      * Remove the timeout callback.  Drop the lock while we're doing that
-     * to reduce lock contention - we don't need it yet anyway.  (Too bad we
-     * are stuck with the cv_* API here, it's doing a little bit too much.)
+     * to reduce lock contention / deadlocks.  (Too bad we are stuck with the
+     * cv_* API here, it's doing a little bit too much.)
      */
     if (fHasTimeout)
     {
+        ASMAtomicWritePtr(&pWait->pvMtx, NULL);
         mutex_exit(pMtx);