[PATCH] uml: fix strace -f

It turns out that we need to check for pending signals when a newly forked
process is run for the first time.  With strace -f, strace needs to know about
the forked process before it gets going.  If it doesn't, then it ptraces some
bogus values into its registers, and the process segfaults.  So, I added calls
to interrupt_end, which does that, plus checks for reschedules.  There
shouldn't be any of those, but x86 does the same thing, so I'm copying that
behavior to be safe.

Signed-off-by: Jeff Dike <[email protected]>
Cc: Paolo 'Blaisorblade' Giarrusso <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

arch/um/kernel/skas/process_kern.c

@@ -68,8 +68,11 @@ void new_thread_handler(int sig)
 	 * 0 if it just exits
 	 */
 	n = run_kernel_thread(fn, arg, &current->thread.exec_buf);
-	if(n == 1)
+	if(n == 1){
+		/* Handle any immediate reschedules or signals */
+		interrupt_end();
 		userspace(&current->thread.regs.regs);
+	}
 	else do_exit(0);
 }
 
@@ -96,6 +99,8 @@ void fork_handler(int sig)
 	schedule_tail(current->thread.prev_sched);
 	current->thread.prev_sched = NULL;
 
+	/* Handle any immediate reschedules or signals */
+	interrupt_end();
 	userspace(&current->thread.regs.regs);
 }