On 2002-05-29 00:24 -0700, Peter Wemm wrote:
> There is a known bug in UMA where it recurses and calls itself with with
> M_WAITOK even if it was explicitly called with M_NOWAIT set. The bug is
> real and would cause a panic if we actually ran low on memory at that
> point.
Just in case anyone more knowledgeable than me knows that to do about
this, here's something that seems to look like this.
A trace that I got when I ran my kernel with WITNESS for a day or so,
was the following. Note the lines marked with an asterisk that
clearly show (unless I am terribly wrong) that UMA is entered twice,
and the WITNESS check fails the second time.
Debugger("witness_sleep")
Stopped at Debugger+0x45: xchgl %ebx,in_Debugger.0
db> trace
Debugger(c02d6500) at Debugger+0x45
witness_sleep(1,0,c02eb711,52c) at witness_sleep+0xf8
* uma_zalloc_arg(c082a640,0,0) at uma_zalloc_arg+0x3e
vm_map_entry_create(c0822000,c5b55150,c69a2000,c0822000,c6424bd4) at
vm_map_entry_create+0x2b
_vm_map_clip_end(c0822000,c5b55150,c69a4000) at _vm_map_clip_end+0x4b
vm_map_delete(c0822000,c69a2000,c69a4000,c69a2000,4) at
vm_map_delete+0x94
vm_map_remove(c0822000,c69a2000,c69a4000,c0321140,1) at
vm_map_remove+0x5b
kmem_free(c0822000,c69a2000,2000,c6424c60,c02818a0) at kmem_free+0x3c
page_free(c69a2000,2000,4) at page_free+0x44
zone_drain(c24f3780) at zone_drain+0x302
zone_foreach(c028159e,c6424d0c,c027f22c,c0321140,1) at
zone_foreach+0x2e
* uma_reclaim(c0321140,1,c02eb4c2,286,c0321140) at uma_reclaim+0x12
vm_pageout_scan(0,c027fcaa,c6424d34,c01a0eaa,0) at
vm_pageout_scan+0x30
vm_pageout(0,c6424d48,c6380a3c,c027fcaa,0) at vm_pageout+0x22d
fork_exit(c027fcaa,0,c6424d48) at fork_exit+0x88
fork_trampoline() at fork_trampoline+0x37
db> c
--
Giorgos Keramidas | FreeBSD: The Power to Serve
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