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sfxge: split sfxge_tx_qdpl_put() into *_locked() and *_unlocked()

Browse Source 
It simplifies understanding of the sfxge_tx_packet_add() logic and
avoids passing of 'locked' to called function.

Reviewed by:    gnn
Sponsored by:   Solarflare Communications, Inc.
MFC after:      2 days
Differential Revision: https://reviews.freebsd.org/D2547
This commit is contained in:
Andrew Rybchenko 2015-05-15 06:50:59 +00:00
parent 22bc53cb48
commit d6e9f7362a
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=282942
2 changed files with 80 additions and 65 deletions
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143
sys/dev/sfxge/sfxge_tx.c
View File

@ -521,18 +521,10 @@ sfxge_tx_qdpl_service(struct sfxge_txq *txq)
}
/*
* Put a packet on the deferred packet list.
*
* If we are called with the txq lock held, we put the packet on the "get
* list", otherwise we atomically push it on the "put list". The swizzle
* function takes care of ordering.
*
* The length of the put list is bounded by SFXGE_TX_MAX_DEFERRED. We
* overload the csum_data field in the mbuf to keep track of this length
* because there is no cheap alternative to avoid races.
* Put a packet on the deferred packet get-list.
*/
static int
sfxge_tx_qdpl_put(struct sfxge_txq *txq, struct mbuf *mbuf, int locked)
sfxge_tx_qdpl_put_locked(struct sfxge_txq *txq, struct mbuf *mbuf)
{
struct sfxge_tx_dpl *stdp;
@ -540,52 +532,66 @@ sfxge_tx_qdpl_put(struct sfxge_txq *txq, struct mbuf *mbuf, int locked)
KASSERT(mbuf->m_nextpkt == NULL, ("mbuf->m_nextpkt != NULL"));
if (locked) {
SFXGE_TXQ_LOCK_ASSERT_OWNED(txq);
SFXGE_TXQ_LOCK_ASSERT_OWNED(txq);
sfxge_tx_qdpl_swizzle(txq);
if (stdp->std_get_count >= stdp->std_get_max) {
txq->get_overflow++;
if (stdp->std_get_count >= stdp->std_get_max) {
txq->get_overflow++;
return (ENOBUFS);
}
if (sfxge_is_mbuf_non_tcp(mbuf)) {
if (stdp->std_get_non_tcp_count >=
stdp->std_get_non_tcp_max) {
txq->get_non_tcp_overflow++;
return (ENOBUFS);
}
if (sfxge_is_mbuf_non_tcp(mbuf)) {
if (stdp->std_get_non_tcp_count >=
stdp->std_get_non_tcp_max) {
txq->get_non_tcp_overflow++;
return (ENOBUFS);
}
stdp->std_get_non_tcp_count++;
}
*(stdp->std_getp) = mbuf;
stdp->std_getp = &mbuf->m_nextpkt;
stdp->std_get_count++;
} else {
volatile uintptr_t *putp;
uintptr_t old;
uintptr_t new;
unsigned old_len;
putp = &stdp->std_put;
new = (uintptr_t)mbuf;
do {
old = *putp;
if (old != 0) {
struct mbuf *mp = (struct mbuf *)old;
old_len = mp->m_pkthdr.csum_data;
} else
old_len = 0;
if (old_len >= stdp->std_put_max) {
atomic_add_long(&txq->put_overflow, 1);
return (ENOBUFS);
}
mbuf->m_pkthdr.csum_data = old_len + 1;
mbuf->m_nextpkt = (void *)old;
} while (atomic_cmpset_ptr(putp, old, new) == 0);
stdp->std_get_non_tcp_count++;
}
*(stdp->std_getp) = mbuf;
stdp->std_getp = &mbuf->m_nextpkt;
stdp->std_get_count++;
return (0);
}
/*
* Put a packet on the deferred packet put-list.
*
* We overload the csum_data field in the mbuf to keep track of this length
* because there is no cheap alternative to avoid races.
*/
static int
sfxge_tx_qdpl_put_unlocked(struct sfxge_txq *txq, struct mbuf *mbuf)
{
struct sfxge_tx_dpl *stdp;
volatile uintptr_t *putp;
uintptr_t old;
uintptr_t new;
unsigned old_len;
KASSERT(mbuf->m_nextpkt == NULL, ("mbuf->m_nextpkt != NULL"));
SFXGE_TXQ_LOCK_ASSERT_NOTOWNED(txq);
stdp = &txq->dpl;
putp = &stdp->std_put;
new = (uintptr_t)mbuf;
do {
old = *putp;
if (old != 0) {
struct mbuf *mp = (struct mbuf *)old;
old_len = mp->m_pkthdr.csum_data;
} else
old_len = 0;
if (old_len >= stdp->std_put_max) {
atomic_add_long(&txq->put_overflow, 1);
return (ENOBUFS);
}
mbuf->m_pkthdr.csum_data = old_len + 1;
mbuf->m_nextpkt = (void *)old;
} while (atomic_cmpset_ptr(putp, old, new) == 0);
return (0);
}
@ -612,22 +618,29 @@ sfxge_tx_packet_add(struct sfxge_txq *txq, struct mbuf *m)
*/
locked = SFXGE_TXQ_TRYLOCK(txq);
if (sfxge_tx_qdpl_put(txq, m, locked) != 0) {
if (locked)
SFXGE_TXQ_UNLOCK(txq);
rc = ENOBUFS;
goto fail;
}
if (locked) {
/* First swizzle put-list to get-list to keep order */
sfxge_tx_qdpl_swizzle(txq);
/*
* Try to grab the lock again.
*
* If we are able to get the lock, we need to process the deferred
* packet list. If we are not able to get the lock, another thread
* is processing the list.
*/
if (!locked)
rc = sfxge_tx_qdpl_put_locked(txq, m);
if (rc != 0) {
SFXGE_TXQ_UNLOCK(txq);
goto fail;
}
} else {
rc = sfxge_tx_qdpl_put_unlocked(txq, m);
if (rc != 0)
goto fail;
/*
* Try to grab the lock again.
*
* If we are able to get the lock, we need to process
* the deferred packet list. If we are not able to get
* the lock, another thread is processing the list.
*/
locked = SFXGE_TXQ_TRYLOCK(txq);
}
if (locked) {
/* Try to service the list. */

2
sys/dev/sfxge/sfxge_tx.h
View File

@ -148,6 +148,8 @@ enum sfxge_txq_type {
mtx_unlock(&(_txq)->lock)
#define SFXGE_TXQ_LOCK_ASSERT_OWNED(_txq) \
mtx_assert(&(_txq)->lock, MA_OWNED)
#define SFXGE_TXQ_LOCK_ASSERT_NOTOWNED(_txq) \
mtx_assert(&(_txq)->lock, MA_NOTOWNED)
struct sfxge_txq {