Re: status of Linux on Alpha?

[Ivan Kokshaysky <ink@jurassic.park.msu.ru>]

On Tue, Apr 27, 2004 at 06:51:24PM +0200, Marc Giger wrote:
> What's the current status of the problem?

Hopefully resolved - thanks to Dru <andru@treshna.com>, who provided
an easy way to reproduce the problem.

What we have in lib/rwsem.c:__rwsem_do_wake():
	int woken, loop;
	^^^
and several lines below:
	loop = woken;
	woken *= RWSEM_ACTIVE_BIAS-RWSEM_WAITING_BIAS;
	woken -= RWSEM_ACTIVE_BIAS;

However, rw_semaphore->count is 64-bit on Alpha, so
RWSEM_WAITING_BIAS has been defined as -0x0000000100000000L.
Obviously, this blows up in the write contention case.

Ivan.

--- linux.orig/lib/rwsem.c	Mon Apr 26 20:11:36 2004
+++ linux/lib/rwsem.c	Tue Apr 27 20:04:14 2004
@@ -40,8 +40,7 @@ static inline struct rw_semaphore *__rws
 {
 	struct rwsem_waiter *waiter;
 	struct list_head *next;
-	signed long oldcount;
-	int woken, loop;
+	signed long oldcount, woken, loop;
 
 	rwsemtrace(sem,"Entering __rwsem_do_wake");