On 09/08/2007, Chris Snook <[EMAIL PROTECTED]> wrote: > From: Chris Snook <[EMAIL PROTECTED]> > > Some architectures currently do not declare the contents of an atomic_t to be > volatile. This causes confusion since atomic_read() might not actually read > anything if an optimizing compiler re-uses a value stored in a register, which > can break code that loops until something external changes the value of an > atomic_t. Avoiding such bugs requires using barrier(), which causes re-loads > of all registers used in the loop, thus hurting performance instead of helping > it, particularly on architectures where it's unnecessary. Since we generally > want to re-read the contents of an atomic variable on every access anyway, > let's standardize the behavior across all architectures and avoid the > performance and correctness problems of requiring the use of barrier() in > loops that expect atomic_t variables to change externally. This is relevant > even on non-smp architectures, since drivers may use atomic operations in > interrupt handlers. > > Signed-off-by: Chris Snook <[EMAIL PROTECTED]> >
Hmm, I thought we were trying to move away from volatile since it is very weakly defined and towards explicit barriers and locks... Points to --> Documentation/volatile-considered-harmful.txt -- Jesper Juhl <[EMAIL PROTECTED]> Don't top-post http://www.catb.org/~esr/jargon/html/T/top-post.html Plain text mails only, please http://www.expita.com/nomime.html - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
