viced-grow-h_maxSlots-20060123

and jhutz@cs.cmu.edu

The size of h_maxSlots as computed based upon the value of
MAX_FILESERVER_THREAD is too small.   It is possible for h_lwpIndex
(in the pthread case) to have produce the same Slot value for multiple
threads.  In that case it is possible for the following to occur:

       X: h_Hold_r(host)
       X: H_UNLOCK
       ...
       E: H_LOCK
       E: Check h_Held_r(host); it is true, so don't hold
       E: H_UNLOCK
       X: H_LOCK
       X: h_Release_r(host)
       X: h_TossStuff_r(host)  [called by h_Release_r]
       X: H_UNLOCK
       E: CheckHost(host)

The end result would be a crash due to a reference to a null field
in the host processed by CheckHost.

This patch is a bit of a hack in that it solves the problem by increasing
the number of slots for threads and does not determine the correct number
of threads the process should be allowed to produce.

diff --git a/src/viced/host.h b/src/viced/host.h
index a095d72..43c5122 100644 (file)
--- a/src/viced/host.h
+++ b/src/viced/host.h
@@ -41,7 +41,7 @@ extern pthread_mutex_t host_glock_mutex;
 #define h_threadsMask          31      /* for remainder */
 
 /* size of the hold array for each host */
-#define h_maxSlots     ((MAX_FILESERVER_THREAD+h_threadsPerSlot-1)>>h_threadsShift)
+#define h_maxSlots     (((MAX_FILESERVER_THREAD+h_threadsPerSlot-1)>>h_threadsShift)+1)
 
 struct Identity {
     char valid;                        /* zero if UUID is unknown */