Commit Graph

146 Commits

Author SHA1 Message Date
Attilio Rao
2feb50bf7d Revert VMCNT_* operations introduction.
Probabilly, a general approach is not the better solution here, so we should
solve the sched_lock protection problems separately.

Requested by: alc
Approved by: jeff (mentor)
2007-05-31 22:52:15 +00:00
Jeff Roberson
222d01951f - define and use VMCNT_{GET,SET,ADD,SUB,PTR} macros for manipulating
vmcnts.  This can be used to abstract away pcpu details but also changes
   to use atomics for all counters now.  This means sched lock is no longer
   responsible for protecting counts in the switch routines.

Contributed by:		Attilio Rao <attilio@FreeBSD.org>
2007-05-18 07:10:50 +00:00
Robert Watson
1e319f6db3 Add uma_set_align() interface, which will be called at most once during
boot by MD code to indicated detected alignment preference.  Rather than
cache alignment being encoded in UMA consumers by defining a global
alignment value of (16 - 1) in UMA_ALIGN_CACHE, UMA_ALIGN_CACHE is now
a special value (-1) that causes UMA to look at registered alignment.  If
no preferred alignment has been selected by MD code, a default alignment
of (16 - 1) will be used.

Currently, no hardware platforms specify alignment; architecture
maintainers will need to modify MD startup code to specify an alignment
if desired.  This must occur before initialization of UMA so that all UMA
zones pick up the requested alignment.

Reviewed by:	jeff, alc
Submitted by:	attilio
2007-02-11 20:13:52 +00:00
Mohan Srinivasan
6c125b8df6 Fix for problems that occur when all mbuf clusters migrate to the mbuf packet
zone. Cluster allocations fail when this happens. Also processes that may have
blocked on cluster allocations will never be woken up. Thanks to rwatson for
an overview of the issue and pointers to the mbuma paper and his tool to dump
out UMA zones.

Reviewed by: andre@
2007-01-25 01:05:23 +00:00
Mohan Srinivasan
7738029183 Fix for a bug where only one process (of multiple) blocked on
maxpages on a zone is woken up, with the rest never being woken up as
a result of the ZFLAG_FULL flag being cleared. Wakeup all such blocked
procsses instead. This change introduces a thundering herd, but since
this should be relatively infrequent, optimizing this (by introducing
a count of blocked processes, for example) may be premature.

Reviewd by: ups@
2007-01-24 22:49:11 +00:00
Robert Watson
635fd50514 Remove uma_zalloc_arg() hack, which coerced M_WAITOK to M_NOWAIT when
allocations were made using improper flags in interrupt context.
Replace with a simple WITNESS warning call.  This restores the
invariant that M_WAITOK allocations will always succeed or die
horribly trying, which is relied on by many UMA consumers.

MFC after:	3 weeks
Discussed with:	jhb
2007-01-10 21:04:43 +00:00
John Baldwin
663b416f16 - Add a new function uma_zone_exhausted() to see if a zone is full.
- Add a printf in swp_pager_meta_build() to warn if the swapzone becomes
  exhausted so that there's at least a warning before a box that runs out
  of swapzone space before running out of swap space deadlocks.

MFC after:	1 week
Reviwed by:	alc
2007-01-05 19:09:01 +00:00
Robert Watson
ae4e9636ac Better align output of "show uma" by moving from displaying the basic
counters of allocs/frees/use for each zone to the same statistics
shown by userspace "vmstat -z".

MFC after:	3 days
2006-10-26 12:55:32 +00:00
Robert Watson
a0d4b0aeaa Fix build of uma_core.c when DDB is not compiled into the kernel by
making uma_zone_sumstat() ifdef DDB, as it's only used with DDB now.

Submitted by:	Wolfram Fenske <Wolfram.Fenske at Student.Uni-Magdeburg.DE>
2006-07-18 01:13:18 +00:00
Robert Watson
eabadd9e4b Remove sysctl_vm_zone() and vm.zone sysctl from 7.x. As of 6.x,
libmemstat(3) is used by vmstat (and friends) to produce more accurate
and more detailed statistics information in a machine-readable way,
and vmstat continues to provide the same text-based front-end.

This change should not be MFC'd.
2006-07-16 22:53:26 +00:00
Robert Watson
4f538c7480 When allocating a bucket to hold a free'd item in UMA fails, don't
report this as an allocation failure for the item type.  The failure
will be separately recorded with the bucket type.  This my eliminate
high mbuf allocation failure counts under some circumstances, which
can be alarming in appearance, but not actually a problem in
practice.

MFC after:	2 weeks
Reported by:	ps, Peter J. Blok <pblok at bsd4all dot org>,
		OxY <oxy at field dot hu>,
		Gabor MICSKO <gmicskoa at szintezis dot hu>
2006-05-21 23:25:32 +00:00
Robert Watson
082dc776db Skip per-cpu caches associated with absent CPUs when generating a
memory statistics record stream via sysctl.

MFC after:	3 days
2006-02-11 19:20:56 +00:00
John Baldwin
ffaf2c55a8 Add a new macro wrapper WITNESS_CHECK() around the witness_warn() function.
The difference between WITNESS_CHECK() and WITNESS_WARN() is that
WITNESS_CHECK() should be used in the places that the return value of
witness_warn() is checked, whereas WITNESS_WARN() should be used in places
where the return value is ignored.  Specifically, in a kernel without
WITNESS enabled, WITNESS_WARN() evaluates to an empty string where as
WITNESS_CHECK evaluates to 0.  I also updated the one place that was
checking the return value of WITNESS_WARN() to use WITNESS_CHECK.
2006-01-27 22:20:15 +00:00
John Baldwin
ca49f12fdb Reduce the scope of one #ifdef to avoid duplicating a SYSCTL_INT() macro
and trim another unneeded #ifdef (it was just around a macro that is
already conditionally defined).
2006-01-06 18:03:45 +00:00
Robert Watson
64a266f9e8 Change format string for u_int64_t to %ju from %llu, in order to use the
correct format string on 64-bit systems.

Pointed out by:	pjd
2005-10-20 21:28:31 +00:00
Robert Watson
48c5777e3d Add a "show uma" command to DDB, which prints out the current stats for
available UMA zones.  Quite useful for post-mortem debugging of memory
leaks without a dump device configured on a panicked box.

MFC after:	2 weeks
2005-10-20 16:39:33 +00:00
Dag-Erling Smørgrav
3803b26bae As alc pointed out to me, vm_page.c 1.305 was incomplete: uma_startup()
still uses the constant UMA_BOOT_PAGES.  Change it to accept boot_pages
as an additional argument.

MFC after:	2 weeks
2005-10-08 21:03:54 +00:00
Alan Cox
f353d3388f Introduce a new lock for the purpose of synchronizing access to the
UMA boot pages.

Disable recursion on the general UMA lock now that startup_alloc() no
longer uses it.

Eliminate the variable uma_boot_free.  It serves no purpose.

Note: This change eliminates a lock-order reversal between a system
map mutex and the UMA lock.  See
http://sources.zabbadoz.net/freebsd/lor.html#109 for details.

MFC after: 3 days
2005-09-09 06:03:08 +00:00
Robert Watson
cbbb4a0089 Rename UMA_MAX_NAME to UTH_MAX_NAME, since it's a maximum in the
monitoring API, which might or might not be the same as the internal
maximum (currently none).

Export flag information on UMA zones -- in particular, whether or
not this is a secondary zone, and so the keg free count should be
considered in that light.

MFC after:	1 day
2005-07-25 00:47:32 +00:00
Robert Watson
f4ff923bdd Further UMA statistics related changes:
- Add a new uma_zfree_internal() flag, ZFREE_STATFREE, which causes it to
  to update the zone's uz_frees statistic.  Previously, the statistic was
  updated unconditionally.

- Use the flag in situations where a "real" free occurs: i.e., one where
  the caller is freeing an allocated item, to be differentiated from
  situations where uma_zfree_internal() is used to tear down the item
  during slab teardown in order to invoke its fini() method.  Also use
  the flag when UMA is freeing its internal objects.

- When exchanging a bucket with the zone from the per-CPU cache when
  freeing an item, flush cache statistics back to the zone (since the
  zone lock and critical section are both held) to match the allocation
  case.

MFC after: 3 days
2005-07-20 18:47:42 +00:00
Robert Watson
ab3a57c04d Use mp_maxid in preference to MAXCPU when creating exports of UMA
per-CPU cache statistics.  UMA sizes the cache array based on the
number of CPUs at boot (mp_maxid + 1), and iterating based on MAXCPU
could read off the end of the array (into the next zone).

Reported by:	yongari
MFC after:	1 week
2005-07-16 11:03:06 +00:00
Robert Watson
08ecce74bc Improve canonicalization of copyrights. Order copyrights by order of
assertion (jeff, bmilekic, rwatson).

Suggested ages ago by:	bde
MFC after:		1 week
2005-07-16 09:51:52 +00:00
Robert Watson
2450bbb872 Move the unlocking of the zone mutex in sysctl_vm_zone_stats() so that
it covers the following of the uc_alloc/freebucket cache pointers.
Originally, I felt that the race wasn't helped by holding the mutex,
hence a comment in the code and not holding it across the cache access.
However, it does improve consistency, as while it doesn't prevent
bucket exchange, it does prevent bucket pointer invalidation.  So a
race in gathering cache free space statistics still can occur, but not
one that follows an invalid bucket pointer, if the mutex is held.

Submitted by:	yongari
MFC after:	1 week
2005-07-16 09:40:34 +00:00
Mike Silbersack
2018f30c01 Increase the flags field for kegs from a 16 to a 32 bit value;
we have exhausted all 16 flags.
2005-07-16 02:23:41 +00:00
Robert Watson
2019094a35 Track UMA(9) allocation failures by zone, and export via sysctl.
Requested by:	victor cruceru <victor dot cruceru at gmail dot com>
MFC after:	1 week
2005-07-15 23:34:39 +00:00
Robert Watson
7a52a97eb3 Introduce a new sysctl, vm.zone_stats, which exports UMA(9) allocator
statistics via a binary structure stream:

- Add structure 'uma_stream_header', which defines a stream version,
  definition of MAXCPUs used in the stream, and the number of zone
  records in the stream.

- Add structure 'uma_type_header', which defines the name, alignment,
  size, resource allocation limits, current pages allocated, preferred
  bucket size, and central zone + keg statistics.

- Add structure 'uma_percpu_stat', which, for each per-CPU cache,
  includes the number of allocations and frees, as well as the number
  of free items in the cache.

- When the sysctl is queried, return a stream header, followed by a
  series of type descriptions, each consisting of a type header
  followed by a series of MAXCPUs uma_percpu_stat structures holding
  per-CPU allocation information.  Typical values of MAXCPU will be
  1 (UP compiled kernel) and 16 (SMP compiled kernel).

This query mechanism allows user space monitoring tools to extract
memory allocation statistics in a machine-readable form, and to do so
at a per-CPU granularity, allowing monitoring of allocation patterns
across CPUs in order to better understand the distribution of work and
memory flow over multiple CPUs.

While here, also export the number of UMA zones as a sysctl
vm.uma_count, in order to assist in sizing user swpace buffers to
receive the stream.

A follow-up commit of libmemstat(3), a library to monitor kernel memory
allocation, will occur in the next few days.  This change directly
supports converting netstat(1)'s "-mb" mode to using UMA-sourced stats
rather than separately maintained mbuf allocator statistics.

MFC after:	1 week
2005-07-14 16:35:13 +00:00
Robert Watson
773df9ab16 In addition to tracking allocs in the zone, also track frees. Add
a zone free counter, as well as a cache free counter.

MFC after:	1 week
2005-07-14 16:17:21 +00:00
Robert Watson
2c743d361a In an earlier world order, UMA would flush per-CPU statistics to the
zone whenever it was moving buckets between the zone and the cache,
or when coalescing statistics across the CPU.  Remove flushing of
statistics to the zone when coalescing statistics as part of sysctl,
as we won't be running on the right CPU to write to the cache
statistics.

Add a missed gathering of statistics: when uma_zalloc_internal()
does a special case allocation of a single item, make sure to update
the zone statistics to represent this.  Previously this case wasn't
accounted for in user-visible statistics.

MFC after:	1 week
2005-07-14 16:13:46 +00:00
Robert Watson
5d1ae027f0 Modify UMA to use critical sections to protect per-CPU caches, rather than
mutexes, which offers lower overhead on both UP and SMP.  When allocating
from or freeing to the per-cpu cache, without INVARIANTS enabled, we now
no longer perform any mutex operations, which offers a 1%-3% performance
improvement in a variety of micro-benchmarks.  We rely on critical
sections to prevent (a) preemption resulting in reentrant access to UMA on
a single CPU, and (b) migration of the thread during access.  In the event
we need to go back to the zone for a new bucket, we release the critical
section to acquire the global zone mutex, and must re-acquire the critical
section and re-evaluate which cache we are accessing in case migration has
occured, or circumstances have changed in the current cache.

Per-CPU cache statistics are now gathered lock-free by the sysctl, which
can result in small races in statistics reporting for caches.

Reviewed by:	bmilekic, jeff (somewhat)
Tested by:	rwatson, kris, gnn, scottl, mike at sentex dot net, others
2005-04-29 18:56:36 +00:00
Alan Cox
b70458aec3 Revert the first part of revision 1.114 and modify the second part. On
architectures implementing uma_small_alloc() pages do not necessarily
belong to the kmem object.
2005-02-24 06:13:01 +00:00
Bosko Milekic
8076cb5289 Well, it seems that I pre-maturely removed the "All rights reserved"
statement from some files, so re-add it for the moment, until the
related legalese is sorted out.  This change affects:

sys/kern/kern_mbuf.c
sys/vm/memguard.c
sys/vm/memguard.h
sys/vm/uma.h
sys/vm/uma_core.c
sys/vm/uma_dbg.c
sys/vm/uma_dbg.h
sys/vm/uma_int.h
2005-02-16 21:45:59 +00:00
Bosko Milekic
500f29d06e Make UMA set the overloaded page->object back to kmem_object for
UMA_ZONE_REFCNT and UMA_ZONE_MALLOC zones, as the page(s) undoubtedly
came from kmem_map for those two.  Previously it would set it back
to NULL for UMA_ZONE_REFCNT zones and although this was probably not
fatal, it added MORE code for no reason.
2005-02-16 20:06:11 +00:00
Bosko Milekic
c5c1b16ec5 While we want the recursion protection for the bucket zones so that
recursion from the VM is handled (and the calling code that allocates
buckets knows how to deal with it), we do not want to prevent allocation
from the slab header zones (slabzone and slabrefzone) if uk_recurse is
not zero for them.  The reason is that it could lead to NULL being
returned for the slab header allocations even in the M_WAITOK
case, and the caller can't handle that (this is also explained in a
comment with this commit).

The problem analysis is documented in our mailing lists:
http://docs.freebsd.org/cgi/getmsg.cgi?fetch=153445+0+archive/2004/freebsd-current/20041231.freebsd-current

(see entire thread for proper context).

Crash dump data provided by: Peter Holm <peter@holm.cc>
2005-01-11 03:33:09 +00:00
Stefan Farfeleder
1e183df21e ISO C requires at least one element in an initialiser list. 2005-01-10 20:30:04 +00:00
Warner Losh
60727d8b86 /* -> /*- for license, minor formatting changes 2005-01-07 02:29:27 +00:00
Bosko Milekic
7b8712053c Add my copyright and update Jeff's copyright on UMA source files,
as per his request.

Discussed with: Jeffrey Roberson
2004-12-26 00:35:12 +00:00
Robert Watson
dc2c7965c0 Abstract the logic to look up the uma_bucket_zone given a desired
number of entries into bucket_zone_lookup(), which helps make more
clear the logic of consumers of bucket zones.

Annotate the behavior of bucket_init() with a comment indicating
how the various data structures, including the bucket lookup tables,
are initialized.
2004-11-06 11:43:30 +00:00
Robert Watson
f9d27e7524 Annotate what bucket_size[] array does; staticize since it's used only
in uma_core.c.
2004-11-06 11:24:40 +00:00
Bosko Milekic
a5a262c6db Fix a INVARIANTS-only bug introduced in Revision 1.104:
IF INVARIANTS is defined, and in the rare case that we have
allocated some objects from the slab and at least one initializer
on at least one of those objects failed, and we need to fail the
allocation and push the uninitialized items back into the slab
caches -- in that scenario, we would fail to [re]set the
bucket cache's ub_bucket item references to NULL, which would
eventually trigger a KASSERT.
2004-10-27 21:19:35 +00:00
Brian Feldman
55fc8c1146 In the previous revision, I did not intend to change the default value
of "nosleepwithlocks."

Submitted by:	ru
2004-10-09 18:51:32 +00:00
Brian Feldman
ab14a3f7aa Fix critical stability problems that can cause UMA mbuf cluster
state management corruption, mbuf leaks, general mbuf corruption,
and at least on i386 a first level splash damage radius that
encompasses up to about half a megabyte of the memory after
an mbuf cluster's allocation slab.  In short, this has caused
instability nightmares anywhere the right kind of network traffic
is present.

When the polymorphic refcount slabs were added to UMA, the new types
were not used pervasively.  In particular, the slab management
structure was turned into one for refcounts, and one for non-refcounts
(supposed to be mostly like the old slab management structure),
but the latter was almost always used through out.  In general, every
access to zones with UMA_ZONE_REFCNT turned on corrupted the
"next free" slab offset offset and the refcount with each other and
with other allocations (on i386, 2 mbuf clusters per 4096 byte slab).

Fix things so that the right type is used to access refcounted zones
where it was not before.  There are additional errors in gross
overestimation of padding, it seems, that would cause a large kegs
(nee zones) to be allocated when small ones would do.  Unless I have
analyzed this incorrectly, it is not directly harmful.
2004-10-08 20:19:29 +00:00
Robert Watson
3659f747f1 Generate KTR trace records for uma_zalloc_arg() and uma_zfree_arg().
This doesn't trace every event of interest in UMA, but provides
enough basic information to explain lock traces and sleep patterns.
2004-08-06 21:52:38 +00:00
Brian Feldman
b23f72e98a * Add a "how" argument to uma_zone constructors and initialization functions
so that they know whether the allocation is supposed to be able to sleep
  or not.
* Allow uma_zone constructors and initialation functions to return either
  success or error.  Almost all of the ones in the tree currently return
  success unconditionally, but mbuf is a notable exception: the packet
  zone constructor wants to be able to fail if it cannot suballocate an
  mbuf cluster, and the mbuf allocators want to be able to fail in general
  in a MAC kernel if the MAC mbuf initializer fails.  This fixes the
  panics people are seeing when they run out of memory for mbuf clusters.
* Allow debug.nosleepwithlocks on WITNESS to be disabled, without changing
  the default.

Both bmilekic and jeff have reviewed the changes made to make failable
zone allocations work.
2004-08-02 00:18:36 +00:00
Bosko Milekic
244f45548a Rework the way slab header storage space is calculated in UMA.
- zone_large_init() stays pretty much the same.
- zone_small_init() will try to stash the slab header in the slab page
  being allocated if the amount of calculated wasted space is less
  than UMA_MAX_WASTE (for both the UMA_ZONE_REFCNT case and regular
  case).  If the amount of wasted space is >= UMA_MAX_WASTE, then
  UMA_ZONE_OFFPAGE will be set and the slab header will be allocated
  separately for better use of space.
- uma_startup() calculates the maximum ipers required in offpage slabs
  (so that the offpage slab header zone(s) can be sized accordingly).
  The algorithm used to calculate this replaces the old calculation
  (which only happened to work coincidentally).  We now iterate over
  possible object sizes, starting from the smallest one, until we
  determine that wastedspace calculated in zone_small_init() might
  end up being greater than UMA_MAX_WASTE, at which point we use the
  found object size to compute the maximum possible ipers.  The
  reason this works is because:
      - wastedspace versus objectsize is a see-saw function with
        local minima all equal to zero and local maxima growing
        directly proportioned to objectsize.  This implies that
        for objects up to or equal a certain objectsize, the see-saw
        remains entirely below UMA_MAX_WASTE, so for those objectsizes
        it is impossible to ever go OFFPAGE for slab headers.
      - ipers (items-per-slab) versus objectsize is an inversely
        proportional function which falls off very quickly (very large
        for small objectsizes).
      - To determine the maximum ipers we'll ever need from OFFPAGE
        slab headers we first find the largest objectsize for which
        we are guaranteed to not go offpage for and use it to compute
        ipers (as though we were offpage).  Since the only objectsizes
        allowed to go offpage are bigger than the found objectsize,
        and since ipers vs objectsize is inversely proportional (and
        monotonically decreasing), then we are guaranteed that the
        ipers computed is always >= what we will ever need in offpage
        slab headers.
- Define UMA_FRITM_SZ and UMA_FRITMREF_SZ to be the actual (possibly
  padded) size of each freelist index so that offset calculations are
  fixed.

This might fix weird data corruption problems and certainly allows
ARM to now boot to at least single-user (via simulator).

Tested on i386 UP by me.
Tested on sparc64 SMP by fenner.
Tested on ARM simulator to single-user by cognet.
2004-07-29 15:25:40 +00:00
Alan Cox
5285558ac2 - Change uma_zone_set_obj() to call kmem_alloc_nofault() instead of
kmem_alloc_pageable().  The difference between these is that an errant
   memory access to the zone will be detected sooner with
   kmem_alloc_nofault().

The following changes serve to eliminate the following lock-order
reversal reported by witness:

 1st 0xc1a3c084 vm object (vm object) @ vm/swap_pager.c:1311
 2nd 0xc07acb00 swap_pager swhash (swap_pager swhash) @ vm/swap_pager.c:1797
 3rd 0xc1804bdc vm object (vm object) @ vm/uma_core.c:931

There is no potential deadlock in this case.  However, witness is unable
to recognize this because vm objects used by UMA have the same type as
ordinary vm objects.  To remedy this, we make the following changes:

 - Add a mutex type argument to VM_OBJECT_LOCK_INIT().
 - Use the mutex type argument to assign distinct types to special
   vm objects such as the kernel object, kmem object, and UMA objects.
 - Define a static swap zone object for use by UMA.  (Only static
   objects are assigned a special mutex type.)
2004-07-22 19:44:49 +00:00
Brian Feldman
0c3c862e21 Since breakage of malloc(9)/uma_zalloc(9) is totally non-optional in
GENERIC/for WITNESS users, make sure the sysctl to disable the behavior
is read-only and always enabled.
2004-07-19 15:05:24 +00:00
Bosko Milekic
0d0837ee6d Introduce debug.nosleepwithlocks sysctl, 0 by default. If set to 1
and WITNESS is not built, then force all M_WAITOK allocations to
M_NOWAIT behavior (transparently).  This is to be used temporarily
if wierd deadlocks are reported because we still have code paths
that perform M_WAITOK allocations with lock(s) held, which can
lead to deadlock.  If WITNESS is compiled, then the sysctl is ignored
and we ask witness to tell us wether we have locks held, converting
to M_NOWAIT behavior only if it tells us that we do.

Note this removes the previous mbuf.h inclusion as well (only needed
by last revision), and cleans up unneeded [artificial] comparisons
to just the mbuf zones.  The problem described above has nothing to
do with previous mbuf wait behavior; it is a general problem.
2004-07-04 16:07:44 +00:00
Brian Feldman
7a708c3626 Reextend the M_WAITOK-disabling-hack to all three of the mbuf-related
zones, and do it by direct comparison of uma_zone_t instead of strcmp.

The mbuf subsystem used to provide M_TRYWAIT/M_DONTWAIT semantics, but
this is mostly no longer the case.  M_WAITOK has taken over the spot
M_TRYWAIT used to have, and for mbuf things, still may return NULL if
the code path is incorrectly holding a mutex going into mbuf allocation
functions.

The M_WAITOK/M_NOWAIT semantics are absolute; though it may deadlock
the system to try to malloc or uma_zalloc something with a mutex held
and M_WAITOK specified, it is absolutely required to not return NULL
and will result in instability and/or security breaches otherwise.
There is still room to add the WITNESS_WARN() to all cases so that
we are notified of the possibility of deadlocks, but it cannot change
the value of the "badness" variable and allow allocation to actually
fail except for the specialized cases which used to be M_TRYWAIT.
2004-07-04 15:59:25 +00:00
Brian Feldman
cf107c1d1a Limit mbuma damage. Suddenly ALL allocations with M_WAITOK are subject
to failing -- that is, allocations via malloc(M_WAITOK) that are required
to never fail -- if WITNESS is not defined.  While everyone should be
running WITNESS, in any case, zone "Mbuf" allocations are really the only
ones that should be screwed with by this hack.

This hack is crashing people, and would continue to do so with or without
WITNESS.  Things shouldn't be allocating with M_WAITOK with locks held,
but it's not okay just to always remove M_WAITOK when !WITNESS.

Reported by:	Bernd Walter <ticso@cicely5.cicely.de>
2004-07-03 18:11:41 +00:00
Bosko Milekic
cc822cb53e Make uma_mtx MTX_RECURSE. Here's why:
The general UMA lock is a recursion-allowed lock because
there is a code path where, while we're still configured
to use startup_alloc() for backend page allocations, we
may end up in uma_reclaim() which calls zone_foreach(zone_drain),
which grabs uma_mtx, only to later call into startup_alloc()
because while freeing we needed to allocate a bucket.  Since
startup_alloc() also takes uma_mtx, we need to be able to
recurse on it.

This exact explanation also added as comment above mtx_init().

Trace showing recursion reported by: Peter Holm <peter-at-holm.cc>
2004-06-23 21:59:03 +00:00