RE: [ipw3945-devel] Panic in iwl3945 driver

Cahill, Ben M
2009-12-02T19:18:12Z

>-----Original Message-----
>From: Zhu Yi [mailto:yi.zhu@intel.com]
>Sent: Wednesday, December 02, 2009 12:43 AM
>To: Maxim Levitsky
>Cc: Chatre, Reinette; linux-wireless; iwlwifi maling list
>Subject: Re: [ipw3945-devel] Panic in iwl3945 driver
>
>On Tue, 2009-12-01 at 17:28 +0800, Zhu Yi wrote:
>> On Tue, 2009-12-01 at 06:35 +0800, Maxim Levitsky wrote:
>> > 0x000000000001668e <iwl3945_rx_reply_tx+302>: lea
>0x38(%r8),%rdi
>> > 0x0000000000016692 <iwl3945_rx_reply_tx+306>: lea
>0x4f(%r8),%rax
>>
>> When this happened, from your previous post, r8 is 0x0 and
>rdi is 0x38.
>> Since "info" is %rdi (see below), this means
>> txq->txb[txq->q.read_ptr].skb[0], aka. r8 is 0.
>>
>> > rate_idx = iwl3945_hwrate_to_plcp_idx(tx_resp->rate);
>> >
>> > 0x0000000000016696 <iwl3945_rx_reply_tx+310>: movb
>$0x0,0x9(%rdi) <---------- RIP
>> > 0x000000000001669a <iwl3945_rx_reply_tx+314>: movb
>$0x0,0xc(%rdi)
>> > 0x000000000001669e <iwl3945_rx_reply_tx+318>: movb
>$0x0,0xf(%rdi)
>> > 0x00000000000166a2 <iwl3945_rx_reply_tx+322>: movb
>$0x0,0x12(%rdi)
>> > 0x00000000000166a6 <iwl3945_rx_reply_tx+326>: movb
>$0x0,0x15(%rdi)
>>
>> This equals to below code in
>ieee80211_tx_info_clear_status(). "info" is
>> %rdi, which is 0x38. That matches NULL pointer dereference at 0x41 in
>> your oops header.
>>
>> for (i = 0; i < IEEE80211_TX_MAX_RATES; i++)
>> info->status.rates[i].count = 0;
>>
>> I guess there is a race for txq->q.read_ptr somewhere.
>Haven't checked
>> though.
>
>OK. 3945 updated write_ptr without regard to read_ptr on the Tx path.
>This messes up our TFD on high load. The patch should fix your problem.

Wow. Could this be happening with other devices as well?

-- Ben --

>
>Signed-off-by: Zhu Yi <yi.zhu@intel.com>
>
>diff --git a/drivers/net/wireless/iwlwifi/iwl3945-base.c
>b/drivers/net/wireless/iwlwifi/iwl3945-base.c
>index 994db4a..b31b34c 100644
>--- a/drivers/net/wireless/iwlwifi/iwl3945-base.c
>+++ b/drivers/net/wireless/iwlwifi/iwl3945-base.c
>@@ -548,6 +548,9 @@ static int iwl3945_tx_skb(struct iwl_priv
>*priv, struct sk_buff *skb)
> txq = &priv->txq[txq_id];
> q = &txq->q;
>
>+ if ((iwl_queue_space(q) < q->high_mark))
>+ goto drop;
>+
> spin_lock_irqsave(&priv->lock, flags);
>
> idx = get_cmd_index(q, q->write_ptr, 0);
>
>
>
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