8e99d66b05
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 |
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