2a339d9e3d
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
80 lines
2.5 KiB
C
80 lines
2.5 KiB
C
/*-
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* Copyright (c) 2010, David Xu <davidxu@freebsd.org>
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice unmodified, this list of conditions, and the following
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* disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*
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* $FreeBSD$
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*
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*/
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#ifndef _SYS__UMTX_H_
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#define _SYS__UMTX_H_
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#include <sys/_types.h>
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#include <sys/_timespec.h>
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struct umutex {
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volatile __lwpid_t m_owner; /* Owner of the mutex */
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__uint32_t m_flags; /* Flags of the mutex */
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__uint32_t m_ceilings[2]; /* Priority protect ceiling */
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__uintptr_t m_rb_lnk; /* Robust linkage */
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#ifndef __LP64__
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__uint32_t m_pad;
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#endif
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__uint32_t m_spare[2];
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};
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struct ucond {
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volatile __uint32_t c_has_waiters; /* Has waiters in kernel */
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__uint32_t c_flags; /* Flags of the condition variable */
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__uint32_t c_clockid; /* Clock id */
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__uint32_t c_spare[1]; /* Spare space */
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};
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struct urwlock {
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volatile __int32_t rw_state;
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__uint32_t rw_flags;
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__uint32_t rw_blocked_readers;
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__uint32_t rw_blocked_writers;
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__uint32_t rw_spare[4];
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};
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struct _usem {
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volatile __uint32_t _has_waiters;
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volatile __uint32_t _count;
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__uint32_t _flags;
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};
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struct _usem2 {
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volatile __uint32_t _count; /* Waiters flag in high bit. */
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__uint32_t _flags;
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};
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struct _umtx_time {
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struct timespec _timeout;
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__uint32_t _flags;
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__uint32_t _clockid;
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};
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#endif /* !_SYS__UMTX_H_ */
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