[Differential] [Closed] D5416: buf_ring/drbr: Add buf_ring_peek_clear_sc and use it in drbr_peek

[Phabricator]

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

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To: sepherosa_gmail.com, network, adrian, delphij, rrs, glebius, kmacy, decui_microsoft.com, honzhan_microsoft.com, howard0su_gmail.com
Cc: freebsd-net-list
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