SLAB_USERCOPY flag was used to indicate PAX
not to kill copies from kernel to userland.
With recent grsecurity patchset and
CONFIG_GRKERNSEC_HIDESYM that enables
CONFIG_PAX_USERCOPY zfs would panic.
Handle newer API while keeping old one functional.
Tested-by: RageLtMan <rageltman@sempervictus>
Reviewed-by: spendergrsec <spender@grsecurity.net>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Kevin Tanguy <kevin.tanguy@ovh.net>
Closes#595
When building SPL within the kernel tree, C99 initializers cause
build failures and need to be converted to C89 as kernel CFLAGS
specify -std=gnu89.
This fix was provided by @behlendorf in #595 discussion notes and
manually implemented in the current master revision.
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: RageLtMan <rageltman@sempervictus>
Closes#597
The main complication from the RT patch set is that the RW semaphore
locks change such that read locks on an rwsem can be taken only by
a single thread. All other threads are locked out. This single
thread can take a read lock multiple times though. The underlying
implementation changes to a mutex with an additional read_depth
count.
The implementation can be best understood by inspecting the RT
patch. rwsem_rt.h and rt.c give the best insight into how RT
rwsem works. My implementation for rwsem_tryupgrade is basically
an inversion of rt_downgrade_write found in rt.c. Please see the
comments in the code.
Unfortunately, I have to drop SPLAT rwlock test4 completely as this
test tries to take multiple locks from different threads, which RT
rwsems do not support. Otherwise SPLAT, zconfig.sh, zpios-sanity.sh
and zfs-tests.sh pass on my Debian-testing VM with the kernel
linux-image-4.8.0-1-rt-amd64.
Tested-by: kernelOfTruth <kerneloftruth@gmail.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Clemens Fruhwirth <clemens@endorphin.org>
Closes zfsonlinux/zfs#5491
Closes#589Closes#308
Commit f58040c0fc should have removed
this comment which is no longer relevant.
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Clemens Fruhwirth <clemens@endorphin.org>
Issue #589
Refactor the code by making splat_test_{init,fini}, splat_subsystem_{init,fini}
into functions. They don't have reason to be macro and it would be too bloated
to inline every call.
Signed-off-by: Chunwei Chen <david.chen@osnexus.com>
Add a dedicated system_delay_taskq for long delay like spa_deadman and
zpl_posix_acl_free. This will allow us to use system_taskq in the manner of
dispatch multiple tasks and call taskq_wait_outstanding.
Reviewed by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Chunwei Chen <david.chen@osnexus.com>
Closes#588
To prevent holding tq_lock for too long.
Before zfsonlinux/zfs@8e71ab9, hogging delay tasks and cat /proc/spl/taskq
would easily cause a lockup. While that bug has been fixed. It's probably
still a good idea to do this just in case task lists grow too large.
Reviewed-by: Tim Chase <tim@chase2k.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Chunwei Chen <david.chen@osnexus.com>
Closes#586
Add the TASKQID_INVALID and TASKQID_INITIAL macros and update the
taskq implementation and test cases to use them. This is solely
for the purposes of readability and introduces no functional change.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Add a minimal implementation of vmem_size() which accounts for the
virtual memory usage of the SPL's kmem cache. This functionality
is only useful on 32-bit systems with a small virtual address space.
The following assumptions are made:
1) The major SPL consumer of virtual memory is the kmem cache.
2) Memory allocated with vmem_alloc() is short lived and can be ignored.
3) Allow a 4MB floor as a generous pad given normal consumption.
4) The spl_kmem_cache_sem only contends with cache create/destroy.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
In Linux 4.9, torvalds/linux@81243ea, group_info changed from 2d array via
->blocks to 1d array via ->gid. We change the spl cred functions accordingly.
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Chunwei Chen <david.chen@osnexus.com>
Closes#581
No need to crhold current_cred(), fix possible leak in splat_cred_test2
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Chunwei Chen <david.chen@osnexus.com>
Closes#556
init_groups has 0 nblocks, therefore calling the current crgetgroups with
init_groups would result in out-of-bound access. We fix this by returning NULL
when nblocks is 0.
Cap crgetngroups to NGROUPS_PER_BLOCK, since crgetgroups will only return
blocks[0].
Also, remove all get_group_info. The cred already holds reference on the
group_info, and cred is not mutable. So there's no reason to hold extra
reference, if we hold cred.
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Chunwei Chen <david.chen@osnexus.com>
Closes#556
When iterating per_cpu values, we need to use for_each_possible_cpu. While
NR_CPUS indicates the number of CPU supported by the kernel, it might not
initialize all of them if the kernel decides it's not possible to use them.
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Chunwei Chen <david.chen@osnexus.com>
Closes#578
Linux 4.8, starting from torvalds/linux@19c5d690e, will set owner to 1 when
read held instead of leave it NULL. So we change the condition to
`rw_owner(rwp) <= 1` in RW_READ_HELD.
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Chunwei Chen <david.chen@osnexus.com>
Closeszfsonlinux/zfs#5233Closes#577
Due to changes in the task_struct the following warning is occurs
when initializing the global p0. Since this structure only exists
for it's address to be taken initialize it in a manor which isn't
sensitive to internal changes to the structure.
module/spl/spl-generic.c:58:1: error: missing braces around
initializer [-Werror=missing-braces]
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#576
Explicitly cast type in splat-rwlock.c test case to silence
the following warning.
warning: format ‘%ld’ expects argument of type ‘long int’,
but argument N has type ‘int’
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#574
When building from the head of a branch a release number is
automatically generated with `git describe` using the last tag
on that branch as the base. For this to work the last tag on the
branch needs to be predictable given the current META file.
This logic was accidentally broken when an -rcX tag was added to
the branch. Update it to search for a VERSION or VERSION-RELEASE
tag.
Reviewed-by: Chris Siebenmann <cks.git01@cs.toronto.edu>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue zfsonlinux/zfs#5105
Closes#572
In order to support ABD with large blocks the spl_kmem_alloc_warn
limit needs to be increased to 64K.
A 16M block requires that pointers be stored for 4096 4K-pages
on an x86_64 system. Each of these pointers is 8 bytes requiring
an allocation of 8*4096=32,768 bytes. The addition of a small
header to this structure pushes the allocation over the default
32K warning threshold.
In addition, fix a small bug where MAX was used instead of MIN
when setting the default. This ensures a reasonable limit is
still set on systems with page sizes larger then 4K.
Reviewed-by: David Quigley <david.quigley@intel.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#571
Update splat_cmd to reference the correct location of the splat utility.
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Liu Hua<liu.hua130@zte.com.cn>
Closes#570
Remove the code that doesn't make any sense.
Reviewed-by: Brian Behlendorf <behlendorf@llnl.gov>
Signed-off-by: Chunwei Chen <david.chen@osnexus.com>
Closes#569
When DEBUG_KMEM_TRACKING is enabled in SPL, we keep tracking all
the buffers alloced by kmem_alloc() and kmem_zalloc(). If a NULL
pointer which indicates no track info in SPL is passed to
spl_kmem_free_track, we just ignore it.
Signed-off-by: GeLiXin <ge.lixin@zte.com.cn>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue zfsonlinux/zfs#4967
Closes#567
Recent 4.X kernels prior to 4.6 require #include of spinlock.h in
order to get the definition of __ARCH_SPIN_LOCK_UNLOCKED which is
used by DEFINE_MUTEX().
Signed-off-by: Tim Chase <tim@chase2k.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#566
Kernel 4.7 added the option to trim the unused exported symbols. In
my testing this showed to be problematic since the PDE_DATA function
was considered unused and as such was trimmed. This in turn caused the
respective test during spl's configure stage to falsely detect that
PDE_DATA is not defined, which in turn caused build failures later.
Handle this situation by adding detection whether CONFIG_TRIM_UNUSED_KSYMS
is enabled and refuse to build against a kernel which has it enabled
Signed-off-by: Nikolay Borisov <n.borisov.lkml@gmail.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#565
For non-rwsem-spinlocks the "count" member was changed from a
"long" to "atomic_long_t" type. A configure check has been
added to detect this change along with new versions of the
_rwsem_tryupgrade() function and RWSEM_COUNT() macro. See
https://github.com/torvalds/linux/commit/8ee62b18 for complete
details.
Signed-off-by: Tim Chase <tim@chase2k.com>
Signed-off-by: Chunwei Chen <david.chen@osnexus.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#563
Signed-off-by: Tom Caputi <tcaputi@datto.com>
Signed-off-by: Tony Hutter <hutter2@llnl.gov>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#562
_ALIGNMENT_REQUIRED needs to be #defined in isa_defs.h in order to
port the Illumos checksum code to ZoL:
4185 add new cryptographic checksums to ZFS: SHA-512, Skein, Edon-R
OpenZFS-issue: https://www.illumos.org/issues/4185
OpenZFS-commit: https://github.com/openzfs/openzfs/commit/45818ee
Signed-off-by: Tony Hutter <hutter2@llnl.gov>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#561
The policy is to try to allocate with KM_NOSLEEP, which will lead to
memory allocation with GFP_ATOMIC, and if it fails, it will launch
an taskq to expand slab space.
This way it should be able to get better NUMA memory locality and
reduce the overhead of context switch.
Signed-off-by: Jinshan Xiong <jinshan.xiong@gmail.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#551
This splat_vprint is using tq_arg->name after tq_arg is freed.
Signed-off-by: Chunwei Chen <david.chen@osnexus.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#557
Current rw_tryupgrade does rw_exit and then rw_tryenter(RW_RWITER), and then
does rw_enter(RW_READER) if it fails. This violate the assumption that
rw_tryupgrade should be atomic and could cause extra contention or even lock
inversion.
This patch we implement a proper rw_tryupgrade. For rwsem-spinlock, we take
the spinlock to check rwsem->count and rwsem->wait_list. For normal rwsem, we
use cmpxchg on rwsem->count to change the value from single reader to single
writer.
Signed-off-by: Chunwei Chen <david.chen@osnexus.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Tim Chase <tim@chase2k.com>
Closes zfsonlinux/zfs#4692
Closes#554
GCC for MIPS only defines _LP64 when 64bit,
while no _ILP32 defined when 32bit.
Signed-off-by: YunQiang Su <syq@debian.org>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#558
wait_event is a macro, so the current implementation will cause re-
evaluation of tq_next_id every time it wakes up. This would cause
taskq_wait_outstanding(tq, 0) to be equivalent to taskq_wait(tq)
Signed-off-by: Chunwei Chen <david.chen@osnexus.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Tim Chase <tim@chase2k.com>
Issue #553
While taskq_destroy would wait for dynamic_taskq to finish its tasks, but it
does not implies the thread being spawned is up and running. This will cause
taskq to be freed before the thread can exit.
We fix this by using tq_nspawn to indicate how many threads are being spawned
before they are inserted to the thread list. And have taskq_destroy to wait
for it to drop to zero.
Signed-off-by: Chunwei Chen <david.chen@osnexus.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Tim Chase <tim@chase2k.com>
Issue #553Closes#550
In 39cd90e, I mistakenly disabled the ability of using absolute expire time in
cv_timedwait_hires. I don't quite sure why I did that, so let's restore it.
Signed-off-by: Chunwei Chen <david.chen@osnexus.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Tim Chase <tim@chase2k.com>
Issue #553
Linux 4.7 changes i_mutex to i_rwsem, and we should used inode_lock and
inode_lock_shared to do exclusive and shared lock respectively.
We use spl_inode_lock{,_shared}() to hide the difference. Note that on older
kernel you'll always take an exclusive lock.
We also add all other inode_lock friends. And nested users now should
explicitly call spl_inode_lock_nested with correct subclass.
Signed-off-by: Chunwei Chen <david.chen@osnexus.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue zfsonlinux/zfs#4665
Closes#549
The problem described in 2a5d574 also applies to XFS's file or inode
fallocate method. Both paths may trigger writeback and expose this
issue, see the full stack below.
When layered on XFS a warning will be emitted under CentOS7 when entering
either the file or inode fallocate method with PF_FSTRANS already set.
To avoid triggering this error PF_FSTRANS is cleared and then reset
in vn_space().
WARNING: at fs/xfs/xfs_aops.c:982 xfs_vm_writepage+0x58b/0x5d0
Call Trace:
[<ffffffff810a1ed5>] warn_slowpath_common+0x95/0xe0
[<ffffffff810a1f3a>] warn_slowpath_null+0x1a/0x20
[<ffffffffa0231fdb>] xfs_vm_writepage+0x58b/0x5d0 [xfs]
[<ffffffff81173ed7>] __writepage+0x17/0x40
[<ffffffff81176f81>] write_cache_pages+0x251/0x530
[<ffffffff811772b1>] generic_writepages+0x51/0x80
[<ffffffffa0230cb0>] xfs_vm_writepages+0x60/0x80 [xfs]
[<ffffffff81177300>] do_writepages+0x20/0x30
[<ffffffff8116a5f5>] __filemap_fdatawrite_range+0xb5/0x100
[<ffffffff8116a6cb>] filemap_write_and_wait_range+0x8b/0xd0
[<ffffffffa0235bb4>] xfs_free_file_space+0xf4/0x520 [xfs]
[<ffffffffa023cbce>] xfs_file_fallocate+0x19e/0x2c0 [xfs]
[<ffffffffa036c6fc>] vn_space+0x3c/0x40 [spl]
[<ffffffffa0434817>] vdev_file_io_start+0x207/0x260 [zfs]
[<ffffffffa047170d>] zio_vdev_io_start+0xad/0x2d0 [zfs]
[<ffffffffa0474942>] zio_execute+0x82/0xe0 [zfs]
[<ffffffffa036ba7d>] taskq_thread+0x28d/0x5a0 [spl]
[<ffffffff810c1777>] kthread+0xd7/0xf0
[<ffffffff8167de2f>] ret_from_fork+0x3f/0x70
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Tim Chase <tim@chase2k.com>
Signed-off-by: Nikolay Borisov <kernel@kyup.com>
Closeszfsonlinux/zfs#4529
This change was lost, somehow, in e5f9a9a. Since the arrays can be
rather large, they need to be allocated with vmem_zalloc() via dfl_alloc()
and freed with vmem_free() via dfl_free().
The new dfl_alloc() function should be used to allocate object of type
dkioc_free_list_t in order that they're allocated from vmem.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Tim Chase <tim@chase2k.com>
Signed-off-by: Nikolay Borisov <kernel@kyup.com>
Closes#543
To reduce mutex footprint, we detect the existence of owner in kernel mutex,
and rely on it if it exists.
Note that before Linux 3.0, mutex owner is of type thread_info. Also note
that, in Linux 3.18, the condition for owner is changed from
CONFIG_DEBUG_MUTEXES || CONFIG_SMP to
CONFIG_DEBUG_MUTEXES || CONFIG_MUTEX_SPIN_ON_OWNER
Signed-off-by: Chunwei Chen <david.chen@osnexus.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#540
Signed-off-by: Dimitri John Ledkov <xnox@ubuntu.com>
Signed-off-by: Richard Yao <ryao@gentoo.org>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#537
When a TQ_NOQUEUE dispatch is done on a dynamic taskq, allow another
thread to be spawned. This will cause TQ_NOQUEUE to behave similarly
as it does with non-dynamic taskqs.
Add support for TQ_NOQUEUE to taskq_dispatch_ent().
Signed-off-by: Tim Chase <tim@onlight.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#530
This implementation of rw_tryupgrade() behaves slightly differently
from its counterparts on other platforms. It drops the RW_READER lock
and then acquires the RW_WRITER lock leaving a small window where no
lock is held. On other platforms the lock is never released during
the upgrade process. This is necessary under Linux because the kernel
does not provide an upgrade function.
There are currently no callers in the ZFS code where this change in
behavior is a problem. In fact, in most cases the code is already
written such that if the upgrade fails the RW_READER lock is dropped
and the caller blocks waiting to acquire the lock as RW_WRITER.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Tim Chase <tim@chase2k.com>
Signed-off-by: Matthew Thode <prometheanfire@gentoo.org>
Closes zfsonlinux/zfs#4388
Closes#534
ZFS on Linux is regularly tested on arm, ppc, ppc64, i686 and x86_64
architectures. Given this the artificial architecture restriction in
the packaging has been removed.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Perf profiling of dd on a zvol revealed that my system spent 3.16% of
its time in random_get_pseudo_bytes(). No SPL consumers need
cryptographic strength entropy, so we can reduce our overhead by
changing the implementation to utilize a fast PRNG.
The Linux kernel did not export a suitable PRNG function until it
exported get_random_int() in Linux 3.10. While we could implement an
autotools check so that we use it when it is available or even try to
access the symbol on older kernels where it is not exported using the
fact that it is exported on newer ones as justification, we can instead
implement our own pseudo-random data generator. For this purpose, I have
written one based on a 128-bit pseudo-random number generator proposed
in a paper by Sebastiano Vigna that itself was based on work by the late
George Marsaglia.
http://vigna.di.unimi.it/ftp/papers/xorshiftplus.pdf
Profiling the same benchmark with an earlier variant of this patch that
used a slightly different generator (roughly same number of
instructions) by the same author showed that time spent in
random_get_pseudo_bytes() dropped to 0.06%. That is a factor of 50
improvement. This particular generator algorithm is also well known to
be fast:
http://xorshift.di.unimi.it/#speed
The benchmark numbers there state that it runs at 1.12ns/64-bits or 7.14
GBps of throughput on an Intel Core i7-4770 in what is presumably a
single-threaded context. Using it in `random_get_pseudo_bytes()` in the
manner I have will probably not reach that level of performance, but it
should be fairly high and many times higher than the Linux
`get_random_bytes()` function that we use now, which runs at 16.3 MB/s
on my Intel Xeon E3-1276v3 processor when measured by using dd on
/dev/urandom.
Also, putting this generator's seed into per-CPU variables allows us to
eliminate overhead from both spin locks and CPU memory barriers, which
is NUMA friendly.
We could have alternatively modified consumers to use something like
`gethrtime() % 3` as suggested by both Matthew Ahrens and Tim Chase, but
that has a few potential problems that this approach avoids:
1. Switching to `gethrtime() % 3` in hot code paths today requires
diverging from illumos-gate and does nothing about potential future
patches from illumos-gate that call our slow `random_get_pseudo_bytes()`
in different hot code paths. Reimplementing `random_get_pseudo_bytes()`
with a per-CPU PRNG avoids both of those things entirely, which means
less work for us in the future.
2. Looking at the code that implements `gethrtime()`, I think it is
unlikely to be faster than this per-CPU PRNG implementation of
`random_get_pseudo_bytes()`. It would be best to go with something fast
now so that there is no point in revisiting this from a performance
perspective.
3. `gethrtime() % 3` can vary in behavior from system to system based on
kernel version, architecture and clock source. In comparison, this
per-CPU PRNG is about ~40 lines of code in `random_get_pseudo_bytes()`
that should behave consistently across all systems regardless of kernel
version, system architecture or machine clock source. It is unlikely
that we would ever need to revisit this per-CPU PRNG while the same
cannot be said for `gethrtime() % 3`.
4. `gethrtime()` uses CPU memory barriers and maybe atomic instructions
depending on the clock source, so replacing `random_get_pseudo_bytes()`
with `gethrtime()` in hot code paths could still require a future person
working on NUMA scalability to reimplement it anyway while this per-CPU
PRNG would not by virtue of using neither CPU memory barriers nor atomic
instructions. Note that I did not check various clock sources for the
presence of atomic instructions. There is simply too much code to read
and given the drawbacks versus this per-cpu PRNG, there is no point in
being certain.
5. I have heard of instances where poor quality pseudo-random numbers
caused problems for HPC code in ways that took more than a year to
identify and were remedied by switching to a higher quality source of
pseudo-random numbers. While filesystems are different than HPC code, I
do not think it is impossible for us to have instances where poor
quality pseudo-random numbers can cause problems. Opting for a well
studied PRNG algorithm that passes tests for statistical randomness over
changing callers to use `gethrtime() % 3` bypasses the need to think
about both whether poor quality pseudo-random numbers can cause problems
and the statistical quality of numbers from `gethrtime() % 3`.
6. `gethrtime()` calls `getrawmonotonic()`, which uses seqlocks. This is
probably not a huge issue, but anyone using kgdb would never be able to
step through a seqlock critical section, which is not a problem either
now or with the per-CPU PRNG:
https://en.wikipedia.org/wiki/Seqlock
The only downside that I can see is that this code's memory requirement
is O(N) where N is NR_CPUS, versus the current code and `gethrtime() %
3`, which are O(1), but that should not be a problem. The seeds will use
64KB of memory at the high end (i.e `NR_CPU == 4096`) and 16 bytes of
memory at the low end (i.e. `NR_CPU == 1`). In either case, we should
only use a few hundred bytes of code for text, especially since
`spl_rand_jump()` should be inlined into `spl_random_init()`, which
should be removed during early boot as part of "Freeing unused kernel
memory". In either case, the memory requirements are minuscule.
Signed-off-by: Richard Yao <ryao@gentoo.org>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Tim Chase <tim@chase2k.com>
Closes#372
This patch add a module parameter spl_taskq_kick. When writing non-zero value
to it, it will scan all the taskq, if a taskq contains a task pending for more
than 5 seconds, it will be forced to spawn a new thread. This is use as an
emergency recovery from deadlock, not a general solution.
Signed-off-by: Chunwei Chen <david.chen@osnexus.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#529
Kevin Tanguy
RageLtMan
Clemens Fruhwirth
Chunwei Chen
Chunwei Chen
Ubuntu
Brian Behlendorf
legend-hua
GeLiXin
Tim Chase
Nikolay Borisov
Tom Caputi
Tony Hutter
Jinshan Xiong
YunQiang Su
David Quigley
Dimitri John Ledkov
Tim Chase
Richard Yao