On 07/02/2012 10:31 AM, Johannes Berg wrote:
Hi Larry, Sorry! I had your other email still marked unread but hadn't gotten around to it :-(Regarding the oops that I reported for PPC architecture that reported "Unable to handle kernel paging request for data at address 0x000004c", I have now repeated it on x86_64 architecture, where the objdump tool is better. The error occurs in the line in __netif_schedule() that says if (!test_and_set_bit(__QDISC_STATE_SCHED, &q->state)) Debug printouts have shown that q is not NULL, and it appears to be in the correct address range. I think q->state is zero; however, q->state cannot be written. Additional testing shows this problem to be another side effect of commit 3a25a8c ("mac80211: add improved HW queue control") for a device with only a single HW queue.Looking at the code again, it seems pretty obviously wrong ... OUCH! I'm not sure which fix is correct though. Should we have software QoS queues for these drivers, but we'll never use them? Then this would work: http://p.sipsolutions.net/e015bf7db9a05887.txt Or we could change the enable code path. Hmm.
That patch does prevent the oops. I was not able to make a connection with the device, but I just acquired it, and I'm not sure of its quality, or that of the driver. It does scan OK, and I think the patch is OK. I'll do more tests with b43legacy later as the machine with that iface is busy. I will also test b43 on the PPC using the open-source firmware.
Although you may want to change the enable code path, some patch will be needed to prevent a regression in 3.5. If this is the one, you may add a "Tested-by" for me.
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