Date: Mon, 29 Feb 2016 03:55:11 +0000 From: Phabricator <phabric-noreply@FreeBSD.org> To: freebsd-net@freebsd.org Subject: [Differential] [Closed] D5416: buf_ring/drbr: Add buf_ring_peek_clear_sc and use it in drbr_peek Message-ID: <3c8297a7aaed44e6fcaa9931b4842923@localhost.localdomain> In-Reply-To: <differential-rev-PHID-DREV-ujjgotek7ybhtamwk6ba-req@FreeBSD.org> References: <differential-rev-PHID-DREV-ujjgotek7ybhtamwk6ba-req@FreeBSD.org>
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[-- Attachment #1 --] This revision was automatically updated to reflect the committed changes. Closed by commit rS296178: buf_ring/drbr: Add buf_ring_peek_clear_sc and use it in drbr_peek (authored by sephe). CHANGED PRIOR TO COMMIT https://reviews.freebsd.org/D5416?vs=13669&id=13866#toc REPOSITORY rS FreeBSD src repository CHANGES SINCE LAST UPDATE https://reviews.freebsd.org/D5416?vs=13669&id=13866 REVISION DETAIL https://reviews.freebsd.org/D5416 AFFECTED FILES head/sys/net/ifq.h head/sys/sys/buf_ring.h CHANGE DETAILS diff --git a/head/sys/sys/buf_ring.h b/head/sys/sys/buf_ring.h --- a/head/sys/sys/buf_ring.h +++ b/head/sys/sys/buf_ring.h @@ -268,6 +268,37 @@ return (br->br_ring[br->br_cons_head]); } +static __inline void * +buf_ring_peek_clear_sc(struct buf_ring *br) +{ +#ifdef DEBUG_BUFRING + void *ret; + + if (!mtx_owned(br->br_lock)) + panic("lock not held on single consumer dequeue"); +#endif + /* + * I believe it is safe to not have a memory barrier + * here because we control cons and tail is worst case + * a lagging indicator so we worst case we might + * return NULL immediately after a buffer has been enqueued + */ + if (br->br_cons_head == br->br_prod_tail) + return (NULL); + +#ifdef DEBUG_BUFRING + /* + * Single consumer, i.e. cons_head will not move while we are + * running, so atomic_swap_ptr() is not necessary here. + */ + ret = br->br_ring[br->br_cons_head]; + br->br_ring[br->br_cons_head] = NULL; + return (ret); +#else + return (br->br_ring[br->br_cons_head]); +#endif +} + static __inline int buf_ring_full(struct buf_ring *br) { diff --git a/head/sys/net/ifq.h b/head/sys/net/ifq.h --- a/head/sys/net/ifq.h +++ b/head/sys/net/ifq.h @@ -369,7 +369,7 @@ return (m); } #endif - return(buf_ring_peek(br)); + return(buf_ring_peek_clear_sc(br)); } static __inline void EMAIL PREFERENCES https://reviews.freebsd.org/settings/panel/emailpreferences/ To: sepherosa_gmail.com, network, adrian, delphij, rrs, glebius, kmacy, decui_microsoft.com, honzhan_microsoft.com, howard0su_gmail.com Cc: freebsd-net-list [-- Attachment #2 --] diff --git a/head/sys/sys/buf_ring.h b/head/sys/sys/buf_ring.h --- a/head/sys/sys/buf_ring.h +++ b/head/sys/sys/buf_ring.h @@ -268,6 +268,37 @@ return (br->br_ring[br->br_cons_head]); } +static __inline void * +buf_ring_peek_clear_sc(struct buf_ring *br) +{ +#ifdef DEBUG_BUFRING + void *ret; + + if (!mtx_owned(br->br_lock)) + panic("lock not held on single consumer dequeue"); +#endif + /* + * I believe it is safe to not have a memory barrier + * here because we control cons and tail is worst case + * a lagging indicator so we worst case we might + * return NULL immediately after a buffer has been enqueued + */ + if (br->br_cons_head == br->br_prod_tail) + return (NULL); + +#ifdef DEBUG_BUFRING + /* + * Single consumer, i.e. cons_head will not move while we are + * running, so atomic_swap_ptr() is not necessary here. + */ + ret = br->br_ring[br->br_cons_head]; + br->br_ring[br->br_cons_head] = NULL; + return (ret); +#else + return (br->br_ring[br->br_cons_head]); +#endif +} + static __inline int buf_ring_full(struct buf_ring *br) { diff --git a/head/sys/net/ifq.h b/head/sys/net/ifq.h --- a/head/sys/net/ifq.h +++ b/head/sys/net/ifq.h @@ -369,7 +369,7 @@ return (m); } #endif - return(buf_ring_peek(br)); + return(buf_ring_peek_clear_sc(br)); } static __inline voidhelp
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