On 09/05/2014 03:38 PM, Marc Gauthier wrote: > Paul E. McKenney wrote: >> On Fri, Sep 05, 2014 at 02:50:31PM -0400, Peter Hurley wrote: >>> On 09/05/2014 02:09 PM, Paul E. McKenney wrote: >>>> This commit documents the fact that it is not safe to use bitfields as >>>> shared variables in synchronization algorithms. It also documents that >>>> CPUs must provide one-byte and two-byte load and store instructions >>> ^ >>> atomic >> >> Here you meant non-atomic? My guess is that you are referring to the >> fact that you could emulate a one-byte store on pre-EV56 Alpha CPUs >> using the ll and sc atomic-read-modify-write instructions, correct? >> >>>> in order to be supported by the Linux kernel. (Michael Cree >>>> has agreed to the resulting non-support of pre-EV56 Alpha CPUs: >>>> https://lkml.org/lkml/2014/9/5/143. > [...] > >>>> + and 64-bit systems, respectively. Note that this means that the >>>> + Linux kernel does not support pre-EV56 Alpha CPUs, because these >>>> + older CPUs do not provide one-byte and two-byte loads and stores. >>> ^ >>> non-atomic >> >> I took this, thank you! > > Eum, am I totally lost, or aren't both of these supposed to say "atomic" ? > > Can't imagine requiring a CPU to provide non-atomic loads and stores > (i.e. requiring old Alpha behavior?). Here's how I read the two statements. First, the commit message: "It [this commit] documents that CPUs [supported by the Linux kernel] _must provide_ atomic one-byte and two-byte naturally aligned loads and stores." Second, in the body of the document: "The Linux kernel no longer supports pre-EV56 Alpha CPUs, because these older CPUs _do not provide_ atomic one-byte and two-byte loads and stores." Regards, Peter Hurley -- To unsubscribe from this list: send the line "unsubscribe linux-arch" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
