Bug#4053: too many of "error 1236: 'binlog truncated in the middle of \

	event' from master"

Since there is no repeatable test case, and this is obviously wrong, this is
the most conservative change that might possibly work.  

The syscall  read()  wasn't checked for a negative return value for an
interrupted read.  The kernel  sys_read()  returns -EINTR, and the "library" 
layer maps that to return value of -1 and sets  errno  to EINTR.  It's 
impossible (on Linux) for  read()  to set errno EINTR without the return 
value being -1 .

So, if we're checking for EINTR behavior, we should not require that the
return value be zero.


mysys/my_read.c:
  The read() syscall should check for negative one, since that (usually) signals
  errors (like being interrupted) and zero (usually) signals end-of-file .

mysys/my_read.c

@@ -36,23 +36,26 @@
 
 uint my_read(File Filedes, byte *Buffer, uint Count, myf MyFlags)
 {
-  uint readbytes,save_count;
+  uint readbytes, save_count;
   DBUG_ENTER("my_read");
   DBUG_PRINT("my",("Fd: %d  Buffer: %lx  Count: %u  MyFlags: %d",
                    Filedes, Buffer, Count, MyFlags));
-  save_count=Count;
+  save_count= Count;
 
   for (;;)
   {
-    errno=0;					/* Linux doesn't reset this */
-    if ((readbytes = (uint) read(Filedes, Buffer, Count)) != Count)
+    errno= 0;					/* Linux doesn't reset this */
+    if ((readbytes= (uint) read(Filedes, Buffer, Count)) != Count)
     {
-      my_errno=errno ? errno : -1;
+      my_errno= errno ? errno : -1;
       DBUG_PRINT("warning",("Read only %ld bytes off %ld from %d, errno: %d",
-			    readbytes,Count,Filedes,my_errno));
+                            readbytes, Count, Filedes, my_errno));
 #ifdef THREAD
-      if (readbytes == 0 && errno == EINTR)
+      if ((int) readbytes <= 0 && errno == EINTR)
+      {
+        DBUG_PRINT("debug", ("my_read() was interrupted and returned %d", (int) readbytes));
         continue;				/* Interrupted */
+      }
 #endif
       if (MyFlags & (MY_WME | MY_FAE | MY_FNABP))
       {
@@ -68,16 +71,16 @@ uint my_read(File Filedes, byte *Buffer, uint Count, myf MyFlags)
         DBUG_RETURN(MY_FILE_ERROR);	/* Return with error */
       if (readbytes > 0 && (MyFlags & MY_FULL_IO))
       {
-	Buffer+=readbytes;
-	Count-=readbytes;
+        Buffer+= readbytes;
+        Count-= readbytes;
         continue;
       }
     }
 
     if (MyFlags & (MY_NABP | MY_FNABP))
-      readbytes=0;			/* Ok on read */
+      readbytes= 0;			/* Ok on read */
     else if (MyFlags & MY_FULL_IO)
-      readbytes=save_count;
+      readbytes= save_count;
     break;
   }
   DBUG_RETURN(readbytes);