mirror_zfs/include
Clemens Fruhwirth 8e99d66b05 Add support for rw semaphore under PREEMPT_RT_FULL
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 #589
Closes #308
2016-12-19 12:45:24 -08:00
..
fs Kernel header installation should respect --prefix 2014-10-28 09:31:48 -07:00
linux Add support for rw semaphore under PREEMPT_RT_FULL 2016-12-19 12:45:24 -08:00
rpc Kernel header installation should respect --prefix 2014-10-28 09:31:48 -07:00
sharefs Kernel header installation should respect --prefix 2014-10-28 09:31:48 -07:00
sys Remove stale comment from rw_tryupgrade() 2016-12-19 11:27:27 -08:00
util Support parallel build trees (VPATH builds) 2015-07-17 12:53:11 -07:00
vm Kernel header installation should respect --prefix 2014-10-28 09:31:48 -07:00
Makefile.am Retire legacy debugging infrastructure 2014-11-19 10:35:07 -08:00
spl-ctl.h Refresh links to web site 2013-03-04 19:09:34 -08:00
splat-ctl.h Update code to use misc_register()/misc_deregister() 2014-10-17 15:07:28 -07:00
strings.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