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Minor design improvements.
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Gareth Rees
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3 changed files with 32 additions and 29 deletions
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@ -135,8 +135,8 @@ Interface
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_`.if.pthreadext.abstract`: A thread is represented by the abstract
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type ``PThreadext``. A ``PThreadext`` object corresponds directly with
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a PThread (of type ``pthread_t``). There may be more than one
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``PThreadext`` object for the same PThread.
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a thread (of type ``pthread_t``). There may be more than one
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``PThreadext`` object for the same thread.
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_`.if.pthreadext.structure`: The structure definition of
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``PThreadext`` (``PThreadextStruct``) is exposed by the interface so
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@ -163,16 +163,16 @@ _`.if.suspend`: Suspends a ``PThreadext`` object (puts it into a
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suspended state). Meets `.req.suspend`_. The object must not already
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be in a suspended state. If the function returns ``ResOK``, the
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context of the thread is returned in contextReturn, and the
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corresponding PThread will not make any progress until it is resumed:
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corresponding thread will not make any progress until it is resumed.
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``Res PThreadextResume(PThreadext pthreadext)``
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_`.if.resume`: Resumes a ``PThreadext`` object. Meets
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`.req.resume`_. The object must already be in a suspended state.
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Puts the object into a non-suspended state. Permits the corresponding
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PThread to make progress again, (although that might not happen
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immediately if there is another suspended ``PThreadext`` object
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corresponding to the same thread):
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_`.if.resume`: Resumes a ``PThreadext`` object. Meets `.req.resume`_.
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The object must already be in a suspended state. Puts the object into
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a non-suspended state. Permits the corresponding thread to make
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progress again, although that might not happen immediately if there is
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another suspended ``PThreadext`` object corresponding to the same
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thread.
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``void PThreadextFinish(PThreadext pthreadext)``
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@ -189,9 +189,9 @@ _`.impl.pthreadext`: The structure definition for a ``PThreadext``
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object is::
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struct PThreadextStruct {
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Sig sig; /* design.mps.sig */
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Sig sig; /* <design/sig/> */
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pthread_t id; /* Thread ID */
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struct sigcontext *suspendedScp; /* sigcontext if suspended */
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MutatorContext context; /* context if suspended */
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RingStruct threadRing; /* ring of suspended threads */
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RingStruct idRing; /* duplicate suspensions for id */
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};
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@ -199,7 +199,7 @@ object is::
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_`.impl.field.id`: The ``id`` field shows which PThread the object
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corresponds to.
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_`.impl.field.scp`: The ``suspendedScp`` field contains the context
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_`.impl.field.context`: The ``context`` field contains the context
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when in a suspended state. Otherwise it is ``NULL``.
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_`.impl.field.threadring`: The ``threadRing`` field is used to chain
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@ -208,29 +208,30 @@ the object onto the suspend ring when it is in the suspended state
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this ring is single.
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_`.impl.field.idring`: The ``idRing`` field is used to group the
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object with other objects corresponding to the same PThread (same
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object with other objects corresponding to the same thread (same
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``id`` field) when they are in the suspended state. When not in a
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suspended state, or when this is the only ``PThreadext`` object with
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this ``id`` in the suspended state, this ring is single.
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_`.impl.global.suspend-ring`: The module maintains a global
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suspend-ring -- a ring of ``PThreadext`` objects which are in a
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_`.impl.global.suspend-ring`: The module maintains a global varaible
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``suspendedRing``, a ring of ``PThreadext`` objects which are in a
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suspended state. This is primarily so that it's possible to determine
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whether a thread is curently suspended anyway because of another
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``PThreadext`` object, when a suspend attempt is made.
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_`.impl.global.victim`: The module maintains a global variable which
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is used to indicate which ``PThreadext`` is the current victim during
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suspend operations. This is used to communicate information between
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the controlling thread and the thread being suspended (the victim).
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The variable has value ``NULL`` at other times.
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_`.impl.global.victim`: The module maintains a global variable
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``suspendingVictim`` which is used to indicate which ``PThreadext`` is
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the current victim during suspend operations. This is used to
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communicate information between the controlling thread and the thread
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being suspended (the victim). The variable has value ``NULL`` at other
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times.
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_`.impl.static.mutex`: We use a lock (mutex) around the suspend and
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resume operations. This protects the state data (the suspend-ring the
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victim: see `.impl.global.suspend-ring`_ and `.impl.global.victim`_
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respectively). Since only one thread can be suspended at a time,
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there's no possibility of two arenas suspending each other by
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concurrently suspending each other's threads.
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resume operations. This protects the state data (the suspend-ring and
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the victim: see `.impl.global.suspend-ring`_ and
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`.impl.global.victim`_ respectively). Since only one thread can be
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suspended at a time, there's no possibility of two arenas suspending
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each other by concurrently suspending each other's threads.
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_`.impl.static.semaphore`: We use a semaphore to synchronize between
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the controlling and victim threads during the suspend operation. See
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@ -375,7 +376,7 @@ Document History
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Copyright and License
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---------------------
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Copyright © 2013-2016 Ravenbrook Limited <http://www.ravenbrook.com/>.
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Copyright © 2013-2018 Ravenbrook Limited <http://www.ravenbrook.com/>.
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All rights reserved. This is an open source license. Contact
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Ravenbrook for commercial licensing options.
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@ -85,7 +85,7 @@ guarantee behaviour in this case. For example, POSIX_ says, "A
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conforming implementation is free to reuse a thread ID after its
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lifetime has ended. If an application attempts to use a thread ID
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whose lifetime has ended, the behavior is undefined." For this reason,
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the documentation for ``mps_thread_dereg()`` specifies that it is an
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the documentation for ``mps_thread_reg()`` specifies that it is an
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error if a thread dies while registered.
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.. _POSIX: http://pubs.opengroup.org/onlinepubs/9699919799/functions/V2_chap02.html#tag_15_09_02
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@ -563,7 +563,9 @@ represented in the obvious way::
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member(ti, ts) ⇔ ((1<<ti) & ts) != 0
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``TraceSet`` is used to represent colour in the Tracer. See
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In the multiple-traces design, each region of memory may be a
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different colour for each trace. Thus the set of traces for which a
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segment is grey (say) is represented by a ``TraceSet``. See
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design.mps.trace_.
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.. _design.mps.trace: trace
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@ -694,7 +696,7 @@ Document History
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Copyright and License
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---------------------
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Copyright © 2013-2017 Ravenbrook Limited <http://www.ravenbrook.com/>.
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Copyright © 2013-2018 Ravenbrook Limited <http://www.ravenbrook.com/>.
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All rights reserved. This is an open source license. Contact
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Ravenbrook for commercial licensing options.
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