This rewrites the error handling policies in the TX status handler.
It tries to be error-tolerant as in "try hard to not crash the machine".
It won't recover from errors (that are bugs in the firmware or driver),
because that's impossible. However, it will return a more or less useful
error message and bail out. It also tries hard to use rate-limited messages
to not flood the syslog in case of a failure.
Signed-off-by: Michael Buesch <mb@xxxxxxxxx>
---
This patch also adds the skb pointer poisoning. I think it's not
strictly needed to catch firmware bugs anymore, because those should
be caught by the in-order check. However, we love defensive coding, so
we try to make the code as robust as possible.
I did not try with openfirmware, but I guess it blows up in the
in-order check there pretty quickly.
Would be cool if somebody could stress this on openfirmware.
Note that if the ordering sanity check fails that can mean three things:
- Either the report ordering on one engine is wrong.
- We missed one report on the engine.
- Or we reported the status to the wrong engine.
Index: wireless-testing/drivers/net/wireless/b43/dma.c
===================================================================
--- wireless-testing.orig/drivers/net/wireless/b43/dma.c 2009-11-18 19:21:17.000000000 +0100
+++ wireless-testing/drivers/net/wireless/b43/dma.c 2009-11-19 21:40:45.000000000 +0100
@@ -874,7 +874,7 @@ static void free_all_descbuffers(struct
for (i = 0; i < ring->nr_slots; i++) {
desc = ring->ops->idx2desc(ring, i, &meta);
- if (!meta->skb) {
+ if (!meta->skb || b43_dma_ptr_is_poisoned(meta->skb)) {
B43_WARN_ON(!ring->tx);
continue;
}
@@ -926,7 +926,7 @@ struct b43_dmaring *b43_setup_dmaring(st
enum b43_dmatype type)
{
struct b43_dmaring *ring;
- int err;
+ int i, err;
dma_addr_t dma_test;
ring = kzalloc(sizeof(*ring), GFP_KERNEL);
@@ -941,6 +941,8 @@ struct b43_dmaring *b43_setup_dmaring(st
GFP_KERNEL);
if (!ring->meta)
goto err_kfree_ring;
+ for (i = 0; i < ring->nr_slots; i++)
+ ring->meta->skb = B43_DMA_PTR_POISON;
ring->type = type;
ring->dev = dev;
@@ -1251,11 +1253,13 @@ struct b43_dmaring *parse_cookie(struct
case 0x5000:
ring = dma->tx_ring_mcast;
break;
- default:
- B43_WARN_ON(1);
}
*slot = (cookie & 0x0FFF);
- B43_WARN_ON(!(ring && *slot >= 0 && *slot < ring->nr_slots));
+ if (unlikely(!ring || *slot < 0 || *slot >= ring->nr_slots)) {
+ b43dbg(dev->wl, "TX-status contains "
+ "invalid cookie: 0x%04X\n", cookie);
+ return NULL;
+ }
return ring;
}
@@ -1494,19 +1498,40 @@ void b43_dma_handle_txstatus(struct b43_
struct b43_dmaring *ring;
struct b43_dmadesc_generic *desc;
struct b43_dmadesc_meta *meta;
- int slot;
+ int slot, firstused;
bool frame_succeed;
ring = parse_cookie(dev, status->cookie, &slot);
if (unlikely(!ring))
return;
-
B43_WARN_ON(!ring->tx);
+
+ /* Sanity check: TX packets are processed in-order on one ring.
+ * Check if the slot deduced from the cookie really is the first
+ * used slot. */
+ firstused = ring->current_slot - ring->used_slots + 1;
+ if (firstused < 0)
+ firstused = ring->nr_slots + firstused;
+ if (unlikely(slot != firstused)) {
+ /* This possibly is a firmware bug and will result in
+ * malfunction, memory leaks and/or stall of DMA functionality. */
+ b43dbg(dev->wl, "Out of order TX status report on DMA ring %d. "
+ "Expected %d, but got %d\n",
+ ring->index, firstused, slot);
+ return;
+ }
+
ops = ring->ops;
while (1) {
- B43_WARN_ON(!(slot >= 0 && slot < ring->nr_slots));
+ B43_WARN_ON(slot < 0 || slot >= ring->nr_slots);
desc = ops->idx2desc(ring, slot, &meta);
+ if (b43_dma_ptr_is_poisoned(meta->skb)) {
+ b43dbg(dev->wl, "Poisoned TX slot %d (first=%d) "
+ "on ring %d\n",
+ slot, firstused, ring->index);
+ break;
+ }
if (meta->skb) {
struct b43_private_tx_info *priv_info =
b43_get_priv_tx_info(IEEE80211_SKB_CB(meta->skb));
@@ -1522,7 +1547,14 @@ void b43_dma_handle_txstatus(struct b43_
if (meta->is_last_fragment) {
struct ieee80211_tx_info *info;
- BUG_ON(!meta->skb);
+ if (unlikely(!meta->skb)) {
+ /* This is a scatter-gather fragment of a frame, so
+ * the skb pointer must not be NULL. */
+ b43dbg(dev->wl, "TX status unexpected NULL skb "
+ "at slot %d (first=%d) on ring %d\n",
+ slot, firstused, ring->index);
+ break;
+ }
info = IEEE80211_SKB_CB(meta->skb);
@@ -1540,20 +1572,29 @@ void b43_dma_handle_txstatus(struct b43_
#endif /* DEBUG */
ieee80211_tx_status(dev->wl->hw, meta->skb);
- /* skb is freed by ieee80211_tx_status() */
- meta->skb = NULL;
+ /* skb will be freed by ieee80211_tx_status().
+ * Poison our pointer. */
+ meta->skb = B43_DMA_PTR_POISON;
} else {
/* No need to call free_descriptor_buffer here, as
* this is only the txhdr, which is not allocated.
*/
- B43_WARN_ON(meta->skb);
+ if (unlikely(meta->skb)) {
+ b43dbg(dev->wl, "TX status unexpected non-NULL skb "
+ "at slot %d (first=%d) on ring %d\n",
+ slot, firstused, ring->index);
+ break;
+ }
}
/* Everything unmapped and free'd. So it's not used anymore. */
ring->used_slots--;
- if (meta->is_last_fragment)
+ if (meta->is_last_fragment) {
+ /* This is the last scatter-gather
+ * fragment of the frame. We are done. */
break;
+ }
slot = next_slot(ring, slot);
}
if (ring->stopped) {
Index: wireless-testing/drivers/net/wireless/b43/dma.h
===================================================================
--- wireless-testing.orig/drivers/net/wireless/b43/dma.h 2009-11-18 19:29:49.000000000 +0100
+++ wireless-testing/drivers/net/wireless/b43/dma.h 2009-11-19 21:16:54.000000000 +0100
@@ -1,7 +1,7 @@
#ifndef B43_DMA_H_
#define B43_DMA_H_
-#include <linux/ieee80211.h>
+#include <linux/err.h>
#include "b43.h"
@@ -164,6 +164,10 @@ struct b43_dmadesc_generic {
#define B43_RXRING_SLOTS 64
#define B43_DMA0_RX_BUFFERSIZE IEEE80211_MAX_FRAME_LEN
+/* Pointer poison */
+#define B43_DMA_PTR_POISON ((void *)ERR_PTR(-ENOMEM))
+#define b43_dma_ptr_is_poisoned(ptr) (unlikely((ptr) == B43_DMA_PTR_POISON))
+
struct sk_buff;
struct b43_private;
--
Greetings, Michael.
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