1. 01 12月, 2016 1 次提交
  2. 24 10月, 2016 2 次提交
  3. 25 3月, 2010 1 次提交
    • R
      Documentation/volatile-considered-harmful.txt: correct cpu_relax() documentation · 091e635e
      Russell King 提交于
      cpu_relax() is documented in volatile-considered-harmful.txt to be a
      memory barrier.  However, everyone with the exception of Blackfin and
      possibly ia64 defines cpu_relax() to be a compiler barrier.
      
      Make the documentation reflect the general concensus.
      
      Linus sayeth:
      
      : I don't think it was ever the intention that it would be seen as anything
      : but a compiler barrier, although it is obviously implied that it might
      : well perform some per-architecture actions that have "memory barrier-like"
      : semantics.
      :
      : After all, the whole and only point of the "cpu_relax()" thing is to tell
      : the CPU that we're busy-looping on some event.
      :
      : And that "event" might be (and often is) about reading the same memory
      : location over and over until it changes to what we want it to be.  So it's
      : quite possible that on various architectures the "cpu_relax()" could be
      : about making sure that such a tight loop on loads doesn't starve cache
      : transactions, for example - and as such look a bit like a memory barrier
      : from a CPU standpoint.
      :
      : But it's not meant to have any kind of architectural memory ordering
      : semantics as far as the kernel is concerned - those must come from other
      : sources.
      Signed-off-by: NRussell King <rmk+kernel@arm.linux.org.uk>
      Cc: <linux-arch@vger.kernel.org>
      Acked-by: NLinus Torvalds <torvalds@linux-foundation.org>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      091e635e
  4. 27 7月, 2008 1 次提交
  5. 24 6月, 2007 1 次提交