Chunwei Chen f58040c0fc Implement a proper rw_tryupgrade ... 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		2016-05-31 11:44:15 -07:00
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bitops_compat.h	Map highbit64() to fls64()	2014-10-17 15:11:50 -07:00
compiler_compat.h	Refresh links to web site	2013-03-04 19:09:34 -08:00
delay_compat.h	Emulate illumos interface cv_timedwait_hires()	2013-11-04 09:49:24 -08:00
file_compat.h	Linux 4.7 compat: inode_lock() and friends	2016-05-20 11:00:14 -07:00
list_compat.h	Refresh links to web site	2013-03-04 19:09:34 -08:00
Makefile.am	Retire spl_module_init()/spl_module_fini()	2015-02-27 13:43:39 -08:00
math64_compat.h	Refresh links to web site	2013-03-04 19:09:34 -08:00
mm_compat.h	Linux 3.12 compat: shrinker semantics	2014-10-28 09:20:13 -07:00
proc_compat.h	Refactor existing code	2015-01-16 13:55:08 -08:00
rwsem_compat.h	Implement a proper rw_tryupgrade	2016-05-31 11:44:15 -07:00
wait_compat.h	Remove compat includes from sys/types.h	2014-11-19 10:35:12 -08:00
zlib_compat.h	Refresh links to web site	2013-03-04 19:09:34 -08:00