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This patch makes some debug messages about 

dropped frames a little more consistent and
fixes an issue in hardstart where I was being
too aggressive about requeing.

I thought the slab allocator would stop handing
out skbuff instances before the system was out
of free memory based upon some kind of limit on
the number of buffers, but this was nonsense.

Therefore, it is NOT a good idea to requeue
when skb allocation fails because this pretty
much basically means we are out of free memory.

Keeping the packets we do not have the RAM to
send and then stopping the transmit queue has
very bad side effects under low/zero memory 
conditions.  

Symptoms may include OOM killer and panics,
among other things.

It's better to drop tx packets when there's no
more RAM than to lock all the tx packets up
in the transmit queue.  Even if more skb
become freed up in the slab cache due to 
transmissions already in progress, evil things
still happen.



git-svn-id: http://madwifi-project.org/svn/madwifi/trunk@3308 0192ed92-7a03-0410-a25b-9323aeb14dbd
This commit is contained in:
mtaylor 2008-01-30 19:33:38 +00:00
parent 874abd03ab
commit 6fbbcf00a0
1 changed files with 24 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

29
ath/if_ath.c
View File

@ -1698,7 +1698,7 @@ ath_uapsd_processtriggers(struct ath_softc *sc, u_int64_t hw_tsf)
}
skb = bf->bf_skb;
if (skb == NULL) {
EPRINTF(sc, "skb is NULL in received ath_buf.\n");
EPRINTF(sc, "Dropping; skb is NULL in received ath_buf.\n");
continue;
}
@ -3172,6 +3172,11 @@ ath_hardstart(struct sk_buff *skb, struct net_device *dev)
struct ath_buf *tbf, *tempbf;
struct sk_buff *tskb;
int framecnt;
/* We will use the requeue flag to denote when to stuff a skb back into
* the OS queues. This should NOT be done under low memory conditions,
* such as skb allocation failure. However, it should be done for the
* case where all the dma buffers are in use (take_txbuf returns null).
*/
int requeue = 0;
#ifdef ATH_SUPERG_FF
unsigned int pktlen;
@ -3198,6 +3203,7 @@ ath_hardstart(struct sk_buff *skb, struct net_device *dev)
if (SKB_CB(skb)->flags & M_RAW) {
bf = ath_take_txbuf(sc);
if (bf == NULL) {
/* All DMA buffers full, safe to try again. */
requeue = 1;
goto hardstart_fail;
}
@ -3218,6 +3224,7 @@ ath_hardstart(struct sk_buff *skb, struct net_device *dev)
/* bypass FF handling */
bf = ath_take_txbuf(sc);
if (bf == NULL) {
/* All DMA buffers full, safe to try again. */
requeue = 1;
goto hardstart_fail;
}
@ -3233,6 +3240,7 @@ ath_hardstart(struct sk_buff *skb, struct net_device *dev)
txq = sc->sc_ac2q[skb->priority];
if (txq->axq_depth > TAIL_DROP_COUNT) {
/* Wish to reserve some DMA buffers, try again later. */
requeue = 1;
goto hardstart_fail;
}
@ -3245,7 +3253,9 @@ ath_hardstart(struct sk_buff *skb, struct net_device *dev)
struct sk_buff *skb_orig = skb;
skb = skb_copy(skb, GFP_ATOMIC);
if (skb == NULL) {
requeue = 1;
DPRINTF(sc, ATH_DEBUG_XMIT,
"Dropping; skb_copy failure.\n");
/* No free RAM, do not requeue! */
goto hardstart_fail;
}
ieee80211_skb_copy_noderef(skb_orig, skb);
@ -3288,7 +3298,7 @@ ath_hardstart(struct sk_buff *skb, struct net_device *dev)
bf = ath_take_txbuf(sc);
if (bf == NULL) {
ATH_TXQ_UNLOCK_IRQ_EARLY(txq);
requeue = 1;
/* All DMA buffers full, safe to try again. */
goto hardstart_fail;
}
DPRINTF(sc, ATH_DEBUG_XMIT | ATH_DEBUG_FF,
@ -3339,6 +3349,7 @@ ath_hardstart(struct sk_buff *skb, struct net_device *dev)
}
bf = ath_take_txbuf(sc);
if (bf == NULL) {
/* All DMA buffers full, safe to try again. */
requeue = 1;
goto hardstart_fail;
}
@ -3356,6 +3367,7 @@ ath_hardstart(struct sk_buff *skb, struct net_device *dev)
bf = ath_take_txbuf(sc);
if (bf == NULL) {
ATH_TXQ_UNLOCK_IRQ_EARLY(txq);
/* All DMA buffers full, safe to try again. */
requeue = 1;
goto hardstart_fail;
}
@ -3370,6 +3382,7 @@ ff_bypass:
bf = ath_take_txbuf(sc);
if (bf == NULL) {
/* All DMA buffers full, safe to try again. */
requeue = 1;
goto hardstart_fail;
}
@ -3458,7 +3471,7 @@ hardstart_fail:
/* Pass control of the skb to the caller (i.e., resources are their
* problem). */
if (requeue) {
/* queue is full, let the kernel backlog the skb */
/* Queue is full, let the kernel backlog the skb */
netif_stop_queue(dev);
sc->sc_devstopped = 1;
/* Stop tracking again we are giving it back*/
@ -6017,6 +6030,9 @@ ath_rxbuf_init(struct ath_softc *sc, struct ath_buf *bf)
skb = ieee80211_dev_alloc_skb(sc->sc_rxbufsize +
extra + sc->sc_cachelsz - 1);
if (skb == NULL) {
DPRINTF(sc, ATH_DEBUG_ANY,
"Dropping; skbuff allocation failed; size: %u!\n",
sc->sc_rxbufsize + extra + sc->sc_cachelsz - 1);
sc->sc_stats.ast_rx_nobuf++;
return -ENOMEM;
}
@ -6131,8 +6147,11 @@ ath_capture(struct net_device *dev, const struct ath_buf *bf,
/* Never copy the SKB, as it is ours on the RX side, and this is the
* last process on the TX side and we only modify our own headers. */
tskb = ath_skb_removepad(skb, 0 /* Copy SKB */);
if (tskb == NULL)
if (tskb == NULL) {
DPRINTF(sc, ATH_DEBUG_ANY,
"Dropping; ath_skb_removepad failed!\n");
return;
}
ieee80211_input_monitor(ic, tskb, bf, tx, tsf, sc);
}