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Chunwei Chen a3c1eb7772 mutex: force serialization on mutex_exit() to fix races 
It is known that mutexes in Linux are not safe when using them to
synchronize the freeing of object in which the mutex is embedded:

http://lwn.net/Articles/575477/

The known places in ZFS which are suspected to suffer from the race
condition are zio->io_lock and dbuf->db_mtx.

* zio uses zio->io_lock and zio->io_cv to synchronize freeing
  between zio_wait() and zio_done().
* dbuf uses dbuf->db_mtx to protect reference counting.

This patch fixes this kind of race by forcing serialization on
mutex_exit() with a spin lock, making the mutex safe by sacrificing
a bit of performance and memory overhead.

This issue most commonly manifests itself as a deadlock in the zio
pipeline caused by a process spinning on the damaged mutex.  Similar
deadlocks have been reported for the dbuf->db_mtx mutex.  And it can
also cause a NULL dereference or bad paging request under the right
circumstances.

This issue any many like it are linked off the zfsonlinux/zfs#2523
issue.  Specifically this fix resolves at least the following
outstanding issues:

zfsonlinux/zfs#401
zfsonlinux/zfs#2523
zfsonlinux/zfs#2679
zfsonlinux/zfs#2684
zfsonlinux/zfs#2704
zfsonlinux/zfs#2708
zfsonlinux/zfs#2517
zfsonlinux/zfs#2827
zfsonlinux/zfs#2850
zfsonlinux/zfs#2891
zfsonlinux/zfs#2897
zfsonlinux/zfs#2247
zfsonlinux/zfs#2939

Signed-off-by: Chunwei Chen <tuxoko@gmail.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Richard Yao <ryao@gentoo.org>
Closes #421
 		2014-12-19 10:18:47 -08:00
..
fm Kernel header installation should respect --prefix 2014-10-28 09:31:48 -07:00
fs Kernel header installation should respect --prefix 2014-10-28 09:31:48 -07:00
sysevent Kernel header installation should respect --prefix 2014-10-28 09:31:48 -07:00
Makefile.am Kernel header installation should respect --prefix 2014-10-28 09:31:48 -07:00
acl.h Refresh links to web site 2013-03-04 19:09:34 -08:00
acl_impl.h Refresh links to web site 2013-03-04 19:09:34 -08:00
atomic.h Remove atomic64_xchg() wrappers 2014-10-17 15:11:50 -07:00
attr.h Refresh links to web site 2013-03-04 19:09:34 -08:00
bitmap.h Refresh links to web site 2013-03-04 19:09:34 -08:00
bootconf.h Refresh links to web site 2013-03-04 19:09:34 -08:00
bootprops.h Refresh links to web site 2013-03-04 19:09:34 -08:00
buf.h Refresh links to web site 2013-03-04 19:09:34 -08:00
byteorder.h Refresh links to web site 2013-03-04 19:09:34 -08:00
callb.h Refresh links to web site 2013-03-04 19:09:34 -08:00
callo.h Emulate illumos interface cv_timedwait_hires() 2013-11-04 09:49:24 -08:00
cmn_err.h Refresh links to web site 2013-03-04 19:09:34 -08:00
compress.h Refresh links to web site 2013-03-04 19:09:34 -08:00
condvar.h Emulate illumos interface cv_timedwait_hires() 2013-11-04 09:49:24 -08:00
conf.h Refresh links to web site 2013-03-04 19:09:34 -08:00
console.h Refresh links to web site 2013-03-04 19:09:34 -08:00
cpupart.h Refresh links to web site 2013-03-04 19:09:34 -08:00
cpuvar.h Refresh links to web site 2013-03-04 19:09:34 -08:00
crc32.h Refresh links to web site 2013-03-04 19:09:34 -08:00
cred.h Remove credential configure checks. 2014-10-17 15:11:51 -07:00
ctype.h Refresh links to web site 2013-03-04 19:09:34 -08:00
ddi.h Refresh links to web site 2013-03-04 19:09:34 -08:00
debug.h Retire legacy debugging infrastructure 2014-11-19 10:35:07 -08:00
dirent.h Refresh links to web site 2013-03-04 19:09:34 -08:00
disp.h Add kpreempt() compatibility macro 2013-10-09 13:52:55 -07:00
dkio.h Refresh links to web site 2013-03-04 19:09:34 -08:00
dklabel.h Refresh links to web site 2013-03-04 19:09:34 -08:00
dnlc.h Remove shrink_{i,d}node_cache() wrappers 2014-10-17 15:11:51 -07:00
dumphdr.h Refresh links to web site 2013-03-04 19:09:34 -08:00
efi_partition.h Refresh links to web site 2013-03-04 19:09:34 -08:00
errno.h Refresh links to web site 2013-03-04 19:09:34 -08:00
extdirent.h Refresh links to web site 2013-03-04 19:09:34 -08:00
fcntl.h Refresh links to web site 2013-03-04 19:09:34 -08:00
file.h Refresh links to web site 2013-03-04 19:09:34 -08:00
idmap.h Refresh links to web site 2013-03-04 19:09:34 -08:00
int_limits.h Refresh links to web site 2013-03-04 19:09:34 -08:00
int_types.h Refresh links to web site 2013-03-04 19:09:34 -08:00
inttypes.h Refresh links to web site 2013-03-04 19:09:34 -08:00
isa_defs.h Add support for aarch64 (ARMv8) 2014-04-25 15:25:32 -07:00
kidmap.h Refresh links to web site 2013-03-04 19:09:34 -08:00
kmem.h Retire legacy debugging infrastructure 2014-11-19 10:35:07 -08:00
kobj.h Refresh links to web site 2013-03-04 19:09:34 -08:00
kstat.h 3537 add kstat_waitq_enter and friends 2013-10-25 13:41:52 -07:00
list.h Refresh links to web site 2013-03-04 19:09:34 -08:00
mkdev.h Refresh links to web site 2013-03-04 19:09:34 -08:00
mntent.h Refresh links to web site 2013-03-04 19:09:34 -08:00
modctl.h Refresh links to web site 2013-03-04 19:09:34 -08:00
mode.h Refresh links to web site 2013-03-04 19:09:34 -08:00
mount.h Refresh links to web site 2013-03-04 19:09:34 -08:00
mutex.h mutex: force serialization on mutex_exit() to fix races 2014-12-19 10:18:47 -08:00
note.h Refresh links to web site 2013-03-04 19:09:34 -08:00
open.h Refresh links to web site 2013-03-04 19:09:34 -08:00
param.h Refresh links to web site 2013-03-04 19:09:34 -08:00
pathname.h Refresh links to web site 2013-03-04 19:09:34 -08:00
policy.h Refresh links to web site 2013-03-04 19:09:34 -08:00
pool.h Refresh links to web site 2013-03-04 19:09:34 -08:00
priv_impl.h Refresh links to web site 2013-03-04 19:09:34 -08:00
proc.h Refresh links to web site 2013-03-04 19:09:34 -08:00
processor.h Refresh links to web site 2013-03-04 19:09:34 -08:00
pset.h Refresh links to web site 2013-03-04 19:09:34 -08:00
random.h Refresh links to web site 2013-03-04 19:09:34 -08:00
refstr.h Refresh links to web site 2013-03-04 19:09:34 -08:00
resource.h Refresh links to web site 2013-03-04 19:09:34 -08:00
rwlock.h Refresh links to web site 2013-03-04 19:09:34 -08:00
sdt.h Define SET_ERROR() 2013-10-09 14:20:46 -07:00
sid.h Refresh links to web site 2013-03-04 19:09:34 -08:00
signal.h Refresh links to web site 2013-03-04 19:09:34 -08:00
stat.h Refresh links to web site 2013-03-04 19:09:34 -08:00
stropts.h Refresh links to web site 2013-03-04 19:09:34 -08:00
sunddi.h Update code to use misc_register()/misc_deregister() 2014-10-17 15:07:28 -07:00
sunldi.h Refresh links to web site 2013-03-04 19:09:34 -08:00
sysdc.h Refresh links to web site 2013-03-04 19:09:34 -08:00
sysevent.h Refresh links to web site 2013-03-04 19:09:34 -08:00
sysmacros.h Map highbit64() to fls64() 2014-10-17 15:11:50 -07:00
systeminfo.h Simplify hostid logic 2014-04-14 09:04:41 -07:00
systm.h Refresh links to web site 2013-03-04 19:09:34 -08:00
t_lock.h Refresh links to web site 2013-03-04 19:09:34 -08:00
taskq.h Refresh links to web site 2013-03-04 19:09:34 -08:00
thread.h De-inline spl_kthread_create(). 2014-04-09 19:17:12 -07:00
time.h Simplify the time compatibility wrappers 2014-10-17 15:11:50 -07:00
timer.h Add ddi_time_after and friends 2014-04-14 09:32:01 -07:00
tsd.h Refresh links to web site 2013-03-04 19:09:34 -08:00
types.h Remove compat includes from sys/types.h 2014-11-19 10:35:12 -08:00
types32.h Refresh links to web site 2013-03-04 19:09:34 -08:00
u8_textprep.h Refresh links to web site 2013-03-04 19:09:34 -08:00
uio.h Refresh links to web site 2013-03-04 19:09:34 -08:00
unistd.h Refresh links to web site 2013-03-04 19:09:34 -08:00
va_list.h Refresh links to web site 2013-03-04 19:09:34 -08:00
varargs.h Refresh links to web site 2013-03-04 19:09:34 -08:00
vfs.h Refresh links to web site 2013-03-04 19:09:34 -08:00
vfs_opreg.h Refresh links to web site 2013-03-04 19:09:34 -08:00
vmsystm.h Remove global memory variables 2014-10-17 15:11:51 -07:00
vnode.h Cleanup vn_rename() and vn_remove() 2014-08-13 16:25:44 -07:00
zmod.h Refresh links to web site 2013-03-04 19:09:34 -08:00
zone.h Refresh links to web site 2013-03-04 19:09:34 -08:00