Date: Sun, 9 Mar 2008 19:58:46 GMT From: Robert Watson <rwatson@FreeBSD.org> To: Perforce Change Reviews <perforce@freebsd.org> Subject: PERFORCE change 137253 for review Message-ID: <200803091958.m29Jwkn2063478@repoman.freebsd.org>
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http://perforce.freebsd.org/chv.cgi?CH=137253 Change 137253 by rwatson@rwatson_cinnamon on 2008/03/09 19:58:30 Add a note of caution on memory ordering, etc, to bpf.h when describing the shared memory header. Affected files ... .. //depot/projects/zcopybpf/src/sys/net/bpf.h#25 edit Differences ... ==== //depot/projects/zcopybpf/src/sys/net/bpf.h#25 (text+ko) ==== @@ -177,7 +177,10 @@ /* * When using zero-copy BPF buffers, a shared memory header is present * allowing the kernel BPF implementation and user process to synchronize - * without using system calls. This structure defines that header. + * without using system calls. This structure defines that header. When + * accessing these fields, appropriate atomic operation and memory barriers + * are required in order not to see stale or out-of-order data; see bpf(4) + * for reference code to access these fields from userspace. * * The layout of this structure is critical, and must not be changed; if must * fit in a single page on all architectures.
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