Author: arybchik
Date: Mon May 18 06:02:22 2015
New Revision: 283048
URL: https://svnweb.freebsd.org/changeset/base/283048
Log:
sfxge: fix overflow queue freeze
If TxQ lock is obtained, deferred packet list shold be serviced even if
the packet addition fails because of overflow.
Without the patch freeze happens if:
- queue is not blocked (i.e. completion does not trigger unblock and service)
- put-list overflow (1024 entries)
- sfxge_tx_packet_add() acquires TxQ lock just as it is released it in
sfxge_tx_qdpl_service() on the second CPU but before pending check
- sfxge_tx_packet_add() swizzles put-list to get-list, fails because of
non-tcp get-list overflow and returns without packet list service
- sfxge_tx_qdpl_service() on the second CPU checks that there are no
pending packets in the put-list and returns
Other possible solution is to guaranee that maximum length of the put-list
is less than maximum length of any get-list.
Reviewed by: gnn
Sponsored by: Solarflare Communications, Inc.
MFC after: 2 days
Differential Revision: https://reviews.freebsd.org/D2562
Modified:
head/sys/dev/sfxge/sfxge_tx.c
Modified: head/sys/dev/sfxge/sfxge_tx.c
==============================================================================
--- head/sys/dev/sfxge/sfxge_tx.c Mon May 18 02:11:09 2015
(r283047)
+++ head/sys/dev/sfxge/sfxge_tx.c Mon May 18 06:02:22 2015
(r283048)
@@ -619,18 +619,12 @@ sfxge_tx_packet_add(struct sfxge_txq *tx
sfxge_tx_qdpl_swizzle(txq);
rc = sfxge_tx_qdpl_put_locked(txq, m);
- if (rc != 0) {
- SFXGE_TXQ_UNLOCK(txq);
- return (rc);
- }
/* Try to service the list. */
sfxge_tx_qdpl_service(txq);
/* Lock has been dropped. */
} else {
rc = sfxge_tx_qdpl_put_unlocked(txq, m);
- if (rc != 0)
- return (rc);
/*
* Try to grab the lock again.
@@ -639,7 +633,7 @@ sfxge_tx_packet_add(struct sfxge_txq *tx
* the deferred packet list. If we are not able to get
* the lock, another thread is processing the list.
*/
- if (SFXGE_TXQ_TRYLOCK(txq)) {
+ if ((rc == 0) && SFXGE_TXQ_TRYLOCK(txq)) {
sfxge_tx_qdpl_service(txq);
/* Lock has been dropped. */
}
@@ -647,7 +641,7 @@ sfxge_tx_packet_add(struct sfxge_txq *tx
SFXGE_TXQ_LOCK_ASSERT_NOTOWNED(txq);
- return (0);
+ return (rc);
}
static void
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