Date: Sat, 3 Aug 2002 15:51:20 -0400 (EDT) From: Jeff Roberson <jroberson@chesapeake.net> To: Bosko Milekic <bmilekic@unixdaemons.com> Cc: "Stephane E. Potvin" <sepotvin@videotron.ca>, <freebsd-hackers@FreeBSD.ORG> Subject: Re: ARM Port: Help with UMA subsystem needed Message-ID: <20020803154945.B26021-100000@mail.chesapeake.net> In-Reply-To: <20020803121419.A35909@unixdaemons.com>
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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
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