Atomic compare_and_swap function

[Altera_Forum]

Hi all, 

 According the header file (D:\altera5\kits\nios2_50\bin\eclipse\plugins\com.microtronix.nios2linux.uClibc_1.4.0\include\bits\atomicity.h), the implemented function is only STUB (not really atomic!).  Does anyone know how to do it really atomic?  I thought that the simplest way is to disable the interrupt when doing this function and re-enable the interrupt afterwards.  So I need to know how to enable/disable interrupt ??  Regards,  Kwok Wong

[Altera_Forum]

--- Quote Start ---  originally posted by kwokwong@Nov 2 2006, 10:14 PM hi all,  according the header file (d:\altera5\kits\nios2_50\bin\eclipse\plugins\com.microtronix.nios2linux.uclibc_1.4.0\include\bits\atomicity.h), the implemented function is only stub (not really atomic!).  does anyone know how to do it really atomic?  i thought that the simplest way is to disable the interrupt when doing this function and re-enable the interrupt afterwards.  so i need to know how to enable/disable interrupt ??  regards,  kwok wong <div align='right'><{post_snapback}> (index.php?act=findpost&pid=19104)  --- quote end ---    --- Quote End ---   It is not implemented, so we need a nios2 version in, uClibc/libc/sysdeps/linux/nios2/bits/atomicity.h Look at other arch, eg, arm,m68k,mips,i386, they use locked exchange instead of disable interrupt. Are there locked instructions in Nios2?

[Altera_Forum]

--- Quote Start ---  originally posted by hippo+nov 2 2006, 11:52 pm--><div class='quotetop'>quote (hippo @ nov 2 2006, 11:52 pm)</div>  --- quote start ---  <!--quotebegin-kwokwong@Nov 2 2006, 10:14 PM hi all,  according the header file (d:\altera5\kits\nios2_50\bin\eclipse\plugins\com.microtronix.nios2linux.uclibc_1.4.0\include\bits\atomicity.h), the implemented function is only stub (not really atomic!).  does anyone know how to do it really atomic?  i thought that the simplest way is to disable the interrupt when doing this function and re-enable the interrupt afterwards.  so i need to know how to enable/disable interrupt ??  regards,  kwok wong <div align='right'><{post_snapback}> (index.php?act=findpost&pid=19104)  --- quote end ---    --- Quote End ---   It is not implemented, so we need a nios2 version in, uClibc/libc/sysdeps/linux/nios2/bits/atomicity.h Look at other arch, eg, arm,m68k,mips,i386, they use locked exchange instead of disable interrupt. Are there locked instructions in Nios2? <div align='right'><{post_snapback}> (index.php?act=findpost&pid=19108)</div> [/b]  --- Quote End ---    $ find uClibc -name "atomic*.h" uClibc/libc/sysdeps/linux/sh/bits/atomic.h uClibc/libc/sysdeps/linux/arm/bits/atomicity.h uClibc/libc/sysdeps/linux/i386/bits/atomic.h uClibc/libc/sysdeps/linux/i386/bits/atomicity.h uClibc/libc/sysdeps/linux/m68k/bits/atomicity.h uClibc/libc/sysdeps/linux/mips/bits/atomic.h uClibc/libc/sysdeps/linux/mips/bits/atomicity.h uClibc/libc/sysdeps/linux/alpha/bits/atomic.h uClibc/libc/sysdeps/linux/alpha/bits/atomicity.h uClibc/libc/sysdeps/linux/h8300/bits/atomicity.h uClibc/libc/sysdeps/linux/sparc/bits/atomicity.h uClibc/libc/sysdeps/linux/common/bits/atomic.h uClibc/libc/sysdeps/linux/common/bits/atomicity.h uClibc/libc/sysdeps/linux/x86_64/bits/atomic.h uClibc/libc/sysdeps/linux/x86_64/bits/atomicity.h uClibc/libc/sysdeps/linux/powerpc/bits/atomic.h uClibc/libc/sysdeps/linux/powerpc/bits/atomicity.h uClibc/include/bits/atomic.h uClibc/include/bits/atomicity.h uClibc/include/atomic.h  If we create uClibc/libc/sysdeps/linux/nios2/bits/atomicity.h ,then it will become uClibc/include/bits/atomicity.h . Otherwise, it will come from uClibc/libc/sysdeps/linux/common/bits/atomicity.h, which is a stub.  If nios2 does not have lock, then we can use disable/enable interrupr, with inline assembly.

[Altera_Forum]

TO_BE_DONE

[Altera_Forum]

Look in include/asm (ie, asm-nios2nommu) /system.h 

Use, local_irq_save(x) // to disable global irq then, local_irq_restore(x) // to enable/restore global irq

[Altera_Forum]

--- Quote Start ---  originally posted by hippo@Nov 7 2006, 12:47 AM look in include/asm (ie, asm-nios2nommu) /system.h use, local_irq_save(x) // to disable global irq then, local_irq_restore(x) // to enable/restore global irq <div align='right'><{post_snapback}> (index.php?act=findpost&pid=19239)  --- quote end ---    --- Quote End ---    Thank you, hippo!  F.Y.I.  Use the macro COMPARE_AND_SWAP in stead of the function compare_and_swap.  E.g.  static inline int __compare_and_swap(volatile int *p, int old_val, int new_val) {   int result;  unsigned long int_context;   /* save int. and disable all interrupts */  local_irq_save(int_context);  result = compare_and_swap((volatile long*)p, old_val, new_val);  /* re-enable interrupt */  local_irq_restore(int_context);  return result; } # define COMPARE_AND_SWAP(addr, old_val, new_val)   __compare_and_swap(addr, old_val, new_val) http://forum.niosforum.com/work2/style_emoticons/<#EMO_DIR#>/smile.gif