haiku/headers/private/system/arch/m68k/arch_real_time_data.h

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/*
* Copyright 2006, Ingo Weinhold <bonefish@cs.tu-berlin.de>.
* All rights reserved. Distributed under the terms of the MIT License.
*/
#ifndef _KERNEL_ARCH_REAL_TIME_DATA_H
#define _KERNEL_ARCH_REAL_TIME_DATA_H
#include <StorageDefs.h>
#include <SupportDefs.h>
#warning M68K: fix system_time()
struct m68k_real_time_data {
vint64 system_time_offset;
};
struct arch_real_time_data {
struct m68k_real_time_data data[2];
vint32 system_time_conversion_factor;
vint32 version;
// Since there're no cheap atomic_{set,get,add}64() on PPC 32 (i.e. one
// that doesn't involve a syscall), we can't have just a single
// system_time_offset and set/get it atomically.
// That's why have our data twice. One set is current (indexed by
// version % 2). When setting the offset, we do that with disabled
// interrupts and protected by a spinlock. We write the new values
// into the other array element and increment the version.
// A reader first reads the version, then the date of interest, and
// finally rechecks the version. If it hasn't changed in the meantime,
// the read value is fine, otherwise it runs the whole procedure again.
//
// system_time_conversion_factor is currently consider constant,
// although that is not necessarily true. We simply don't support
// changing conversion factors at the moment.
};
#endif /* _KERNEL_ARCH_REAL_TIME_DATA_H */