Re: Potential 2.2.8 scheduler bugs

Andrea Arcangeli (andrea@suse.de)
Fri, 14 May 1999 01:59:39 +0200 (CEST)


On Thu, 13 May 1999, Dimitris Michailidis wrote:

>to zombie). The wmb() in __schedule_tail() should make all CPUs see
>that has_cpu=1 for this process. This is before the process becomes a

I thought that running wmb() in cpu 1 was forcing the CPU1 to write
ordered in memory, but nothing more. So according to me writing in-order
using CPU 1, doesn't imply that CPU 2 will be forced to read in-order too
from memory (and even if it will be forced in x86 that's not enough).

This is why I think that to force CPU 2 to read in-order we must use
rmb(), even if the other cpu uses wmb() to allow us to read the right
thing if we synchronize our reads too.

I would like to know if my understanding of wmb() is wrong ;).

Andrea Arcangeli

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