Do not allocate a callout for all crashdumps, not just when you panic.

sys/dev/ata/ata-disk.c

@@ -388,7 +388,7 @@ ad_transfer(struct ad_request *request)
     if (request->donecount == 0) {
 
 	/* start timeout for this transfer */
-	if (panicstr)
+	if (dumping)
 	    request->timeout_handle.callout = NULL;
 	else
 	    request->timeout_handle = 

sys/kern/kern_shutdown.c

@@ -109,6 +109,8 @@ watchdog_tickle_fn wdog_tickler = NULL;
  */
 const char *panicstr;
 
+int dumping;				 /* system is dumping */
+
 static void boot(int) __dead2;
 static void dumpsys(void);
 static void poweroff_wait(void *, int);
@@ -469,7 +471,6 @@ static void
 dumpsys(void)
 {
 	int	error;
-	static int dumping;
 
 	savectx(&dumppcb);
 #ifdef __i386__

sys/sys/systm.h

@@ -50,6 +50,7 @@ extern int securelevel;		/* system security level (see init(8)) */
 
 extern int cold;		/* nonzero if we are doing a cold boot */
 extern const char *panicstr;	/* panic message */
+extern int dumping;		/* system is dumping */
 extern int safepri;		/* safe ipl when cold or panicing */
 extern char version[];		/* system version */
 extern char copyright[];	/* system copyright */