bitmap: add atomic set functions
Use atomic_or() for atomic bitmaps where several threads may set bits at the same time. This avoids the race condition between threads loading an element, bitwise ORing, and then storing the element. When setting all bits in a word we can avoid atomic ops and instead just use an smp_mb() at the end. Most bitmap users don't need atomicity so introduce new functions. Signed-off-by: NStefan Hajnoczi <stefanha@redhat.com> Message-Id: <1417519399-3166-2-git-send-email-stefanha@redhat.com> [Avoid barrier in the single word case, use full barrier instead of write. - Paolo] Reviewed-by: NFam Zheng <famz@redhat.com> Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>
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