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72 lines
2.2 KiB
ReStructuredText
72 lines
2.2 KiB
ReStructuredText
PR_Interrupt
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============
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Sets the interrupt request for a target thread.
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Syntax
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------
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.. code::
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#include <prthread.h>
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PRStatus PR_Interrupt(PRThread *thread);
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Parameter
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~~~~~~~~~
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:ref:`PR_Interrupt` has the following parameter:
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``thread``
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The thread whose interrupt request you want to set.
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Returns
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~~~~~~~
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The function returns one of the following values:
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- If the specified thread is currently blocked, ``PR_SUCCESS``.
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- Otherwise, ``PR_FAILURE``.
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Description
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-----------
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The purpose of :ref:`PR_Interrupt` is to request that a thread performing
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some task stop what it is doing and return to some control point. It is
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assumed that a control point has been mutually arranged between the
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thread doing the interrupting and the thread being interrupted. When the
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interrupted thread reaches the prearranged point, it can communicate
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with its peer to discover the real reason behind the change in plans.
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The interrupt request remains in the thread's state until it is
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delivered exactly once or explicitly canceled. The interrupted thread
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returns ``PR_FAILURE`` (-1) with an error code (see :ref:`PR_GetError`) for
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blocking operations that return a :ref:`PRStatus` (such as I/O operations,
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monitor waits, or waiting on a condition). To check whether the thread
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was interrupted, compare the result of :ref:`PR_GetError` with
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``PR_PENDING_INTERRUPT_ERROR``.
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:ref:`PR_Interrupt` may itself fail if the target thread is invalid.
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Bugs
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----
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:ref:`PR_Interrupt` has the following limitations and known bugs:
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- There can be a delay for a thread to be interrupted from a blocking
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I/O function. In all NSPR implementations, the maximum delay is at
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most five seconds. In the pthreads-based implementation on Unix, the
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maximum delay is 0.1 seconds.
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- File I/O is considered instantaneous, so file I/O functions cannot be
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interrupted. Unfortunately the standard input, output, and error
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streams are treated as files by NSPR, so a :ref:`PR_Read` call on
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``PR_STDIN`` cannot be interrupted even though it may block
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indefinitely.
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- In the NT implementation, :ref:`PR_Connect` cannot be interrupted.
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- In the NT implementation, a file descriptor is not usable and must be
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closed after an I/O function on the file descriptor is interrupted.
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