freebsd-dev/sys/compat
Konstantin Belousov 2a339d9e3d Add implementation of robust mutexes, hopefully close enough to the
intention of the POSIX IEEE Std 1003.1TM-2008/Cor 1-2013.

A robust mutex is guaranteed to be cleared by the system upon either
thread or process owner termination while the mutex is held.  The next
mutex locker is then notified about inconsistent mutex state and can
execute (or abandon) corrective actions.

The patch mostly consists of small changes here and there, adding
neccessary checks for the inconsistent and abandoned conditions into
existing paths.  Additionally, the thread exit handler was extended to
iterate over the userspace-maintained list of owned robust mutexes,
unlocking and marking as terminated each of them.

The list of owned robust mutexes cannot be maintained atomically
synchronous with the mutex lock state (it is possible in kernel, but
is too expensive).  Instead, for the duration of lock or unlock
operation, the current mutex is remembered in a special slot that is
also checked by the kernel at thread termination.

Kernel must be aware about the per-thread location of the heads of
robust mutex lists and the current active mutex slot.  When a thread
touches a robust mutex for the first time, a new umtx op syscall is
issued which informs about location of lists heads.

The umtx sleep queues for PP and PI mutexes are split between
non-robust and robust.

Somewhat unrelated changes in the patch:
1. Style.
2. The fix for proper tdfind() call use in umtxq_sleep_pi() for shared
   pi mutexes.
3. Removal of the userspace struct pthread_mutex m_owner field.
4. The sysctl kern.ipc.umtx_vnode_persistent is added, which controls
   the lifetime of the shared mutex associated with a vnode' page.

Reviewed by:	jilles (previous version, supposedly the objection was fixed)
Discussed with:	brooks, Martin Simmons <martin@lispworks.com> (some aspects)
Tested by:	pho
Sponsored by:	The FreeBSD Foundation
2016-05-17 09:56:22 +00:00
..
cloudabi Add implementation of robust mutexes, hopefully close enough to the 2016-05-17 09:56:22 +00:00
cloudabi64 Make CloudABI's way of doing TLS more friendly to userspace emulators. 2016-04-06 11:11:31 +00:00
freebsd32 The sendfile(2) allows to send extra data from userspace before the file 2016-03-29 19:57:11 +00:00
ia32 Implement vsyscall hack. Prior to 2.13 glibc uses vsyscall 2016-01-09 20:18:53 +00:00
linprocfs linprocfs_doproclimits: Initialize error return before use 2016-04-20 01:03:06 +00:00
linsysfs Add support to the jail framework to be able to mount linsysfs(5) and 2015-07-19 08:52:35 +00:00
linux Add implementation of robust mutexes, hopefully close enough to the 2016-05-17 09:56:22 +00:00
linuxkpi/common Only lock Giant when needed in the LinuxKPI. 2016-05-16 17:41:25 +00:00
ndis ndis: spelling fixes in comments. 2016-04-30 00:35:46 +00:00
netbsd Remove some more NetBSD compat shims and other unused bits from these 2012-09-10 18:49:49 +00:00
svr4 Allow to build svr4 module with SYSV support separatelly from the kernel build. 2016-04-23 20:31:18 +00:00
x86bios x86bios: spelling fix in a comment. 2016-04-30 00:34:04 +00:00