benaphore.h

Go to the documentation of this file.

/*
    Copyright (c) 2002, Thomas Kurschel


    Part of Open SCSI bus manager
        
    Benaphore definition
*/

#ifndef _BENAPHORE_H
#define _BENAPHORE_H

#include <KernelExport.h>

typedef struct {
    int32   ben;
    sem_id  sem;
} benaphore;

 
#define INIT_BEN(x, prefix) ( (x)->ben = -1, (x)->sem = create_sem(0, #prefix " benaphore"), (x)->sem )
#define DELETE_BEN(x)       delete_sem((x)->sem);

#if __GNUC__ && _X86_ && !DEBUG

#ifdef NO_PIC

// don't use normal inline as this _does_ incur overhead;
// also, we have to include the xxx_sem call in the assembler code
// as this is the only way to use flags directly (else we had to create
// a temporary variable); this function call leads to the following:
// - it's not PIC safe, making it unusable in user mode!
// - function calls clobber eax, ecx, edx and memory
#define ACQUIRE_BEN( x ) \
__asm__ __volatile__ ( \
    "lock incl %0;" \
    "jng 1f;" \
    "push %1;" \
    "call acquire_sem;" \
    "add  $4,%%esp;" \
    "1:;" \
    : "=m" ((x)->ben) \
    : "m" ((x)->sem), "0" ((x)->ben) \
    : "ax", "cx", "dx" \
);

#define RELEASE_BEN( x ) \
__asm__ __volatile__ ( \
    "lock decl %0;" \
    "jl 1f;" \
    "push %1;" \
    "call release_sem;" \
    "add  $4,%%esp;" \
    "1:;" \
    : "=m" ((x)->ben) \
    : "m" ((x)->sem), "0" ((x)->ben) \
    : "ax", "cx", "dx" \
);

#else   // NO_PIC

// larger, but PIC-safe version

#define ACQUIRE_BEN( x ) \
{ \
    char not_idle; \
\
    __asm__ __volatile__ ( \
        "lock incl %0;" \
        "setg %1" \
        : "=m" ((x)->ben), "=qm" (not_idle) \
        : "0" ((x)->ben) \
    ); \
\
    if( not_idle ) \
        acquire_sem( (x)->sem ); \
}

#define RELEASE_BEN( x ) \
{ \
    char not_idle; \
\
    __asm__ __volatile__ ( \
        "lock decl %0;" \
        "setge %1" \
        : "=m" ((x)->ben), "=qm" (not_idle) \
        : "0" ((x)->ben) \
    ); \
\
    if( not_idle ) \
        release_sem( (x)->sem ); \
}

#endif

#else   // __GNUC__ && _X86_

#define ACQUIRE_BEN(x) \
    if((atomic_add(&((x)->ben), 1)) >= 0) \
        acquire_sem((x)->sem);
        
#define RELEASE_BEN(x) \
    if((atomic_add(&((x)->ben), -1)) > 0) \
        release_sem((x)->sem);

#endif


#endif

---

Copyright 2005 by yellowTAB GmbH, Be Inc., Palm Source Inc. and their respective legal successors
All rights reserved.