From owner-freebsd-hackers Sat Aug 3 12:51:59 2002 Delivered-To: freebsd-hackers@freebsd.org Received: from mx1.FreeBSD.org (mx1.FreeBSD.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 05BB537B400 for ; Sat, 3 Aug 2002 12:51:56 -0700 (PDT) Received: from mail.chesapeake.net (chesapeake.net [205.130.220.14]) by mx1.FreeBSD.org (Postfix) with ESMTP id 3CC7D43E42 for ; Sat, 3 Aug 2002 12:51:55 -0700 (PDT) (envelope-from jroberson@chesapeake.net) Received: from localhost (jroberson@localhost) by mail.chesapeake.net (8.11.6/8.11.3) with ESMTP id g73JpK987052; Sat, 3 Aug 2002 15:51:20 -0400 (EDT) (envelope-from jroberson@chesapeake.net) Date: Sat, 3 Aug 2002 15:51:20 -0400 (EDT) From: Jeff Roberson To: Bosko Milekic Cc: "Stephane E. Potvin" , Subject: Re: ARM Port: Help with UMA subsystem needed In-Reply-To: <20020803121419.A35909@unixdaemons.com> Message-ID: <20020803154945.B26021-100000@mail.chesapeake.net> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-freebsd-hackers@FreeBSD.ORG Precedence: bulk List-ID: List-Archive: (Web Archive) List-Help: (List Instructions) List-Subscribe: List-Unsubscribe: X-Loop: FreeBSD.ORG On Sat, 3 Aug 2002, Bosko Milekic wrote: > > On Sat, Aug 03, 2002 at 11:07:11AM -0400, Stephane E. Potvin wrote: > > > > I just found out that reverting this commit fixes the problem. Any > > ideas about why other arches don't encouter the problem? > > > > jeff 2002/06/19 13:49:44 PDT > > > > Modified files: > > sys/vm uma.h uma_core.c > > Log: > > - Remove bogus use of kmem_alloc that was inherited from the old zone > > allocator. > > This looks like the problem, or at least that which uncovers the > problem. The pmap code is calling the zone allocator as well and > what happens is that you recurse on the kmem_map lockmgr lock because > you allocate recursively from kmem_map. Previously, we could also > allocate from kernel_map, if the kernel_map lockmgr lock wasn't held, > so this way if we had a recursive call we would get around this > problem. I think this whole thing is flaky in general (if this was > the way to get around recursion, we should fix it). > > JHB and/or JeffR: why is the kmem_map lockmgr lock not recursive? > These locks can not be made recurisve safely. In this case you would just recurse forever and never satisfy the allocation. All pmap modules do something like the following: static void * pmap_allocf(uma_zone_t zone, int bytes, u_int8_t *flags, int wait) { *flags = UMA_SLAB_PRIV; return (void *)kmem_alloc(kernel_map, bytes); } pvzone = uma_zcreate("PV ENTRY", sizeof (struct pv_entry), NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, UMA_ZONE_VM); uma_zone_set_allocf(pvzone, pmap_allocf); uma_prealloc(pvzone, initial_pvs); Is arm using a seperate allocf? Jeff To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message