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#ifndef __PARISC_BARRIER_H #define __PARISC_BARRIER_H /* ** This is simply the barrier() macro from linux/kernel.h but when serial.c ** uses tqueue.h uses smp_mb() defined using barrier(), linux/kernel.h ** hasn't yet been included yet so it fails, thus repeating the macro here. ** ** PA-RISC architecture allows for weakly ordered memory accesses although ** none of the processors use it. There is a strong ordered bit that is ** set in the O-bit of the page directory entry. Operating systems that ** can not tolerate out of order accesses should set this bit when mapping ** pages. The O-bit of the PSW should also be set to 1 (I don't believe any ** of the processor implemented the PSW O-bit). The PCX-W ERS states that ** the TLB O-bit is not implemented so the page directory does not need to ** have the O-bit set when mapping pages (section 3.1). This section also ** states that the PSW Y, Z, G, and O bits are not implemented. ** So it looks like nothing needs to be done for parisc-linux (yet). ** (thanks to chada for the above comment -ggg) ** ** The __asm__ op below simple prevents gcc/ld from reordering ** instructions across the mb() "call". */ #define mb() __asm__ __volatile__("":::"memory") /* barrier() */ #define rmb() mb() #define wmb() mb() #define smp_mb() mb() #define smp_rmb() mb() #define smp_wmb() mb() #define smp_read_barrier_depends() do { } while(0) #define read_barrier_depends() do { } while(0) #define set_mb(var, value) do { var = value; mb(); } while (0) #endif /* __PARISC_BARRIER_H */ |