FreeBSD/Linux Kernel Cross Reference
sys/man/task_ras_control.man

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    .\" HISTORY
    .\" $Log:       task_ras_control.man,v $
    .\" Revision 2.2  93/03/18  15:15:15  mrt
    .\"             Created by Brian Bershad
    .\"     [93/03/18            bershad]
    .\" 
    .\" 
    .TH task_ras_control 2 7/21/92
    .CM 4
    .SH NAME
    .nf
    task_ras_control  \-  set pc range of task's restartable atomic sequence
    .SH SYNOPSIS
    .nf
    .ft B
    #include <mach.h>
    
    .nf
    .ft B
    kern_return_t
    task_ras_control(
            task_t      target_task,
            vm_offset_t start_pc,
            vm_offset_t end_pc,
            int         flavor)
    .fi
    .ft P
    .SH ARGUMENTS
    .TP 15
    .B
    target_task
    The task for which the sequence should be set.
    .TP 15
    .B 
    start_pc
    The starting address of this restartable atomic sequence.
    .TP 15
    .B 
    end_pc
    The ending address of this restartable atomic sequence.
    .TP 15
    .B 
    flavor
    The particular operation that should be applied to this restartable atomic
    sequence.  Flavor can be one of
    .B TASK_RAS_CONTROL_PURGE_ALL
    , which removes all registered sequences for this task,
    .B TASK_RAS_CONTROL_PURGE_ONE
    , which removes the named registered sequence for this task, and
    .B TASK_RAS_CONTROL_PURGE_ALL_AND_INSTALL_ONE
    , which atomically removes all registered sequences and installs the named 
    sequence,
    .B TASK_RAS_CONTROL_INSTALL_ONE
    , which installs this sequence.
    
    
    .SH DESCRIPTION
    
    Manipulates a task's set of
    restartable atomic sequences.  If a sequence is installed, and
    any thread in the task is preempted
    within the range [start_pc,end_pc], then the thread is resumed at
    start_pc.  This enables applications to build atomic sequences which,
    when executed to completion, will have executed atomically.
    Restartable atomic sequences are intended to be used on systems  that
    do not have hardware support for low-overhead atomic primitives.
    
    As a thread can be rolled-back, the code in the sequence should have
    no side effects other than a final store at end_pc. The kernel does
    not guarantee that the sequence is restartable.  It assumes the
    application knows what it's doing.
    
    A task may have a finite number of atomic sequences that is defined at
    compile time.
   
   .SH DIAGNOSTICS
   .TP 25
   KERN_SUCCESS
   The operation has been performed.
   .TP 25
   KERN_INVALID_ADDRESS
   The start_pc or end_pc values are not a valid address for the requested
   operation. For example, it is invalid to purge a sequence that has not been
   registered.
   .TP 25
   KERN_RESOURCE_SHORTAGE
   An attempt was made to install more restartable atomic sequences for a task
   than can be supported by the kernel.
   .TP 25
   KERN_INVALID_VALUE
   A bad flavor was specified.
   .TP 25
   KERN_INVALID_ARGUMENT
   .B target_task
   is not a task.
   .TP 25
   .B
   KERN_FAILURE
   The call is not not supported on this configuration.
   
   .SH SEE ALSO
   Fast Mutual Exclusion for Uniprocessors (1992 ASPLOS).
   
   
   
   

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