interface xdc.runtime.knl.IGateProcessSupport
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Interface for OS specific back-end

The xdc.runtime.knl package contains modules that provide typical OS services. These xdc.runtime.knl modules require proxies to be bound to an OS specific delegate. This specifies the interface to be implemented by the OS specific delegate for xdc.runtime.knl.GateProcess module. [ more ... ]
XDCspec summary sourced in xdc/runtime/knl/IGateProcessSupport.xdc
interface IGateProcessSupport {  ...
// inherits xdc.runtime.knl.IGateThreadSupport
    // inherits xdc.runtime.IGateProvider
        // inherits xdc.runtime.IModule
instance:  ...
XDCspec declarations sourced in xdc/runtime/knl/IGateProcessSupport.xdc
package xdc.runtime.knl;
 
interface IGateProcessSupport inherits IGateThreadSupport {
module-wide constants & types
    const Int GETREFCOUNT_FAILED// Status returned by getReferenceCount when there is an error = -1;
    const Int Q_BLOCKING// Blocking quality = 1;
    const Int Q_PREEMPTING// Preempting quality = 2;
module-wide config parameters
    metaonly config Types.Common$ common$// Common module configuration parameters;
module-wide functions
    Bool query// Runtime test for a particular gate quality(Int qual);
 
    metaonly Bool queryMeta// Configuration time test for a particular gate quality(Int qual);
 
 
instance:
per-instance config parameters
    config Int key// globally unique key for SysV-style semaphore = -1;
per-instance creation
    create// Create an instance-object();
per-instance functions
    IArg enter// Enter this gate();
    Int getReferenceCount// Get the number of processes with references to this Gate(Error.Block *err);
    Void leave// Leave this gate(IArg key);
}
DETAILS
The xdc.runtime.knl package contains modules that provide typical OS services. These xdc.runtime.knl modules require proxies to be bound to an OS specific delegate. This specifies the interface to be implemented by the OS specific delegate for xdc.runtime.knl.GateProcess module.
The implementation of IGateThreadSupport should try to implement a gate that supports priority inversion.
 
const IGateProcessSupport.GETREFCOUNT_FAILED
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Status returned by getReferenceCount when there is an error

XDCspec declarations sourced in xdc/runtime/knl/IGateProcessSupport.xdc
const Int GETREFCOUNT_FAILED = -1;
 
 
const IGateProcessSupport.Q_BLOCKING
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Blocking quality

XDCspec declarations sourced in xdc/runtime/knl/IGateProcessSupport.xdc
const Int Q_BLOCKING = 1;
 
DETAILS
Gates with this "quality" may cause the calling thread to block; i.e., suspend execution until another thread leaves the gate.
 
const IGateProcessSupport.Q_PREEMPTING
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Preempting quality

XDCspec declarations sourced in xdc/runtime/knl/IGateProcessSupport.xdc
const Int Q_PREEMPTING = 2;
 
DETAILS
Gates with this "quality" allow other threads to preempt the thread that has already entered the gate.
 
metaonly config IGateProcessSupport.common$  // module-wide
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Common module configuration parameters

XDCspec declarations sourced in xdc/runtime/knl/IGateProcessSupport.xdc
metaonly config Types.Common$ common$;
 
DETAILS
All modules have this configuration parameter. Its name contains the '$' character to ensure it does not conflict with configuration parameters declared by the module. This allows new configuration parameters to be added in the future without any chance of breaking existing modules.
 
IGateProcessSupport.query()  // module-wide
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Runtime test for a particular gate quality

XDCspec declarations sourced in xdc/runtime/knl/IGateProcessSupport.xdc
Bool query(Int qual);
 
ARGUMENTS
qual — constant describing a quality
RETURNS
Returns TRUE if the gate has the given quality, and FALSE otherwise, which includes the case when the gate does not recognize the constant describing the quality.
 
metaonly IGateProcessSupport.queryMeta()  // module-wide
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Configuration time test for a particular gate quality

XDCspec declarations sourced in xdc/runtime/knl/IGateProcessSupport.xdc
metaonly Bool queryMeta(Int qual);
 
ARGUMENTS
qual — constant describing a quality
RETURNS
Returns TRUE if the gate has the given quality, and FALSE otherwise, which includes the case when the gate does not recognize the constant describing the quality.
 
config IGateProcessSupport.key  // instance
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globally unique key for SysV-style semaphore

XDCspec declarations sourced in xdc/runtime/knl/IGateProcessSupport.xdc
config Int key = -1;
 
Instance Creation
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XDCspec declarations sourced in xdc/runtime/knl/IGateProcessSupport.xdc
create();
// Create an instance-object
DETAILS
This function creates a new GateProcess object which is initialized to count. All gates created with the same key reference the same underlying synchronization object and work between processes. The underlying synchronization object should be automatically deleted when all references to it have been deleted, and the reference count should An implementation for a platform on which this is technically impossible (e.g. an operating system that does not support multiple processes) may provide a 'toy' implemenation with behavior matching that of IGateProcessSupport.
 
IGateProcessSupport.enter()  // instance
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Enter this gate

XDCspec declarations sourced in xdc/runtime/knl/IGateProcessSupport.xdc
IArg enter();
 
DETAILS
Each gate provider can implement mutual exclusion using different algorithms; e.g., disabling all scheduling, disabling the scheduling of all threads below a specified "priority level", suspending the caller when the gate has been entered by another thread and re-enabling it when the the other thread leaves the gate. However, in all cases, after this method returns that caller has exclusive access to the data protected by this gate.
A thread may reenter a gate without blocking or failing.
RETURNS
Returns a "key" that is used to leave this gate; this value is used to restore thread preemption to the state that existed just prior to entering this gate.
 
IGateProcessSupport.getReferenceCount()  // instance
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Get the number of processes with references to this Gate

XDCspec declarations sourced in xdc/runtime/knl/IGateProcessSupport.xdc
Int getReferenceCount(Error.Block *err);
 
ARGUMENTS
err — Pointer to Error.Block
RETURNS
Returns the number of processes that possess a reference to this gate, or GETREFCOUNT_FAILED if an error occured. A 'toy' implementation should always return 0.
 
IGateProcessSupport.leave()  // instance
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Leave this gate

XDCspec declarations sourced in xdc/runtime/knl/IGateProcessSupport.xdc
Void leave(IArg key);
 
ARGUMENTS
key — the value returned by a matching call to enter
DETAILS
This method is only called by threads that have previously entered this gate via enter. After this method returns, the caller must not access the data structure protected by this gate (unless the caller has entered the gate more than once and other calls to leave remain to balance the number of previous calls to enter).
generated on Thu, 27 Sep 2012 23:21:08 GMT