process.h

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#ifndef _IPXE_PROCESS_H
#define _IPXE_PROCESS_H

/** @file
 *
 * Processes
 *
 */

FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );

#include <ipxe/list.h>
#include <ipxe/refcnt.h>
#include <ipxe/tables.h>

/** A process */
struct process {
        /** List of processes */
        struct list_head list;
        /** Process descriptor */
        struct process_descriptor *desc;
        /** Reference counter
         *
         * If this process is not part of a reference-counted object,
         * this field may be NULL.
         */
        struct refcnt *refcnt;
};

/** A process descriptor */
struct process_descriptor {
        /** Process name */
        const char *name;
        /** Offset of process within containing object */
        size_t offset;
        /**
         * Single-step the process
         *
         * This method should execute a single step of the process.
         * Returning from this method is isomorphic to yielding the
         * CPU to another process.
         */
        void ( * step ) ( void *object );
        /** Automatically reschedule the process */
        int reschedule;
};

/**
 * Define a process step() method
 *
 * @v object_type       Implementing method's expected object type
 * @v step              Implementing method
 * @ret step            Process step method
 */
#define PROC_STEP( object_type, step )                                        \
        ( ( ( ( typeof ( step ) * ) NULL ) ==                                 \
            ( ( void ( * ) ( object_type *object ) ) NULL ) ) ?               \
          ( void ( * ) ( void *object ) ) step :                              \
          ( void ( * ) ( void *object ) ) step )

/**
 * Calculate offset of process within containing object
 *
 * @v object_type       Containing object data type
 * @v name              Process name (i.e. field within object data type)
 * @ret offset          Offset of process within containing object
 */
#define process_offset( object_type, name )                                   \
        ( ( ( ( typeof ( ( ( object_type * ) NULL )->name ) * ) NULL )        \
            == ( ( struct process * ) NULL ) )                                \
          ? offsetof ( object_type, name )                                    \
          : offsetof ( object_type, name ) )

/**
 * Define a process descriptor
 *
 * @v object_type       Containing object data type
 * @v process           Process name (i.e. field within object data type)
 * @v step              Process' step() method
 * @ret desc            Object interface descriptor
 */
#define PROC_DESC( object_type, process, _step ) {                            \
                .name = #_step,                                               \
                .offset = process_offset ( object_type, process ),            \
                .step = PROC_STEP ( object_type, _step ),                     \
                .reschedule = 1,                                              \
        }

/**
 * Define a process descriptor for a process that runs only once
 *
 * @v object_type       Containing object data type
 * @v process           Process name (i.e. field within object data type)
 * @v step              Process' step() method
 * @ret desc            Object interface descriptor
 */
#define PROC_DESC_ONCE( object_type, process, _step ) {                       \
                .name = #_step,                                               \
                .offset = process_offset ( object_type, process ),            \
                .step = PROC_STEP ( object_type, _step ),                     \
                .reschedule = 0,                                              \
        }

/**
 * Define a process descriptor for a pure process
 *
 * A pure process is a process that does not have a containing object.
 *
 * @v step              Process' step() method
 * @ret desc            Object interface descriptor
 */
#define PROC_DESC_PURE( _step ) {                                             \
                .name = #_step,                                               \
                .offset = 0,                                                  \
                .step = PROC_STEP ( struct process, _step ),                  \
                .reschedule = 1,                                              \
        }

extern void * __attribute__ (( pure ))
process_object ( struct process *process );
extern void process_add ( struct process *process );
extern void process_del ( struct process *process );
extern void step ( void );

/**
 * Initialise a static process
 *
 * @v process           Process
 * @v desc              Process descriptor
 */
#define PROC_INIT( _process, _desc ) {                                        \
                .list = LIST_HEAD_INIT ( (_process).list ),                   \
                .desc = (_desc),                                              \
                .refcnt = NULL,                                               \
        }

/**
 * Initialise process without adding to process list
 *
 * @v process           Process
 * @v desc              Process descriptor
 * @v refcnt            Containing object reference count, or NULL
 */
static inline __attribute__ (( always_inline )) void
process_init_stopped ( struct process *process,
                       struct process_descriptor *desc,
                       struct refcnt *refcnt ) {
        INIT_LIST_HEAD ( &process->list );
        process->desc = desc;
        process->refcnt = refcnt;
}

/**
 * Initialise process and add to process list
 *
 * @v process           Process
 * @v desc              Process descriptor
 * @v refcnt            Containing object reference count, or NULL
 */
static inline __attribute__ (( always_inline )) void
process_init ( struct process *process,
               struct process_descriptor *desc,
               struct refcnt *refcnt ) {
        process_init_stopped ( process, desc, refcnt );
        process_add ( process );
}

/**
 * Check if process is running
 *
 * @v process           Process
 * @ret running         Process is running
 */
static inline __attribute__ (( always_inline )) int
process_running ( struct process *process ) {
        return ( ! list_empty ( &process->list ) );
}

/** Permanent process table */
#define PERMANENT_PROCESSES __table ( struct process, "processes" )

/**
 * Declare a permanent process
 *
 * Permanent processes will be automatically added to the process list
 * at initialisation time.
 */
#define __permanent_process __table_entry ( PERMANENT_PROCESSES, 01 )

/** Define a permanent process
 *
 */
#define PERMANENT_PROCESS( name, step )                                       \
static struct process_descriptor name ## _desc = PROC_DESC_PURE ( step );     \
struct process name __permanent_process = PROC_INIT ( name, & name ## _desc );

/**
 * Find debugging colourisation for a process
 *
 * @v process           Process
 * @ret col             Debugging colourisation
 *
 * Use as the first argument to DBGC() or equivalent macro.
 */
#define PROC_COL( process ) process_object ( process )

/** printf() format string for PROC_DBG() */
#define PROC_FMT "%p %s()"

/**
 * printf() arguments for representing a process
 *
 * @v process           Process
 * @ret args            printf() argument list corresponding to PROC_FMT
 */
#define PROC_DBG( process ) process_object ( process ), (process)->desc->name

#endif /* _IPXE_PROCESS_H */