> -----Original Message----- > From: Kalle Valo [mailto:kvalo@xxxxxxxxxxxxxxxx] > Sent: Tuesday, November 26, 2013 6:40 PM > To: Liu Hui-R64343 > Cc: linux-arm-kernel@xxxxxxxxxxxxxxxxxxx; linville@xxxxxxxxxxxxx; linux- > wireless@xxxxxxxxxxxxxxx; netdev@xxxxxxxxxxxxxxx; linux- > kernel@xxxxxxxxxxxxxxx; ath6kl-devel@xxxxxxxxxxxxxxxx > Subject: Re: [PATCH] ath6kl: sdio: fix system panic when doing wifi > stress test > > Hi Jason, > > Jason Liu <r64343@xxxxxxxxxxxxx> writes: > > > When did the wifi iperf test, meet one following kernel panic: > > command: iperf -c $TARGET_IP -i 5 -t 50 -w 1M > > > > Unable to handle kernel paging request at virtual address 1a480000 pgd > > = 80004000 [1a480000] *pgd=00000000 Internal error: Oops: 805 [#1] SMP > > ARM > > [...] > > > The kernel panic is caused by the sg_buf is not set correctly with the > > following code when compiled with Yocto GCC 4.8.1: > > > > drivers/net/wireless/ath/ath6kl/hif.h: > > struct hif_scatter_req { > > struct list_head list; > > /* address for the read/write operation */ > > u32 addr; > > ... > > > > /* bounce buffer for upper layers to copy to/from */ > > u8 *virt_dma_buf; > > > > struct hif_scatter_item scat_list[1]; > > > > u32 scat_q_depth; > > }; > > > > (Note: the scat_req.scat_list[] will dynamiclly grow with run-time) > > There's actually a major bug right there, scat_list can corrupt > scat_q_depth. > > > The GCC 4.8.1 compiler will not do the for-loop till scat_entries, > > instead, it only run one round loop. This may be caused by that the > > GCC 4.8.1 thought that the scat_list only have one item and then no > > need to do full iteration, but this is simply wrong by looking at the > > assebly code. This will cause the sg buffer not get set when > scat_entries > 1 and thus lead to kernel panic. > > > > This patch is a workaround to the GCC 4.8.1 complier issue by passing > > the entry address of the scat_req->scat_list to the for-loop and > > interate it, then, GCC 4.8.1 will do the full for-loop correctly. > > (Note: This issue not observed with GCC 4.7.2, only found on the GCC > > 4.8.1) > > > > This patch does not change any function logic and no any performance > downgrade. > > [...] > > > + scat_list = &scat_req->scat_list[0]; > > + > > /* assemble SG list */ > > - for (i = 0; i < scat_req->scat_entries; i++, sg++) { > > + for (i = 0; i < scat_req->scat_entries; i++, sg++, scat_list++) { > > ath6kl_dbg(ATH6KL_DBG_SCATTER, "%d: addr:0x%p, len:%d\n", > > - i, scat_req->scat_list[i].buf, > > - scat_req->scat_list[i].len); > > + i, scat_list->buf, scat_list->len); > > > > - sg_set_buf(sg, scat_req->scat_list[i].buf, > > - scat_req->scat_list[i].len); > > + sg_set_buf(sg, scat_list->buf, scat_list->len); > > } > > Working around the problem by adding a temporary variable makes me a bit > worried, I would rather fix the root cause. Is the root cause by that we > define the field with scat_list[1]? Yes, this is what I assumed. > > Does the patch below help? It would also fix the corruption with > scat_q_depth. Please note that I have only compile tested it. And I might > have also missed something important, so please review it carefully. Yes, Firstly, I have looked at the asm code and the compiler(gcc 4.8.1) works correctly after applying the following patch. Secondly, I have tested the patch with compiler(gcc 4.8.1) on the real HW, and it works fine too. Without the patch, the kernel crash will happen 100%. Thus, for the patch: Acked-by: Jason Liu <r64343@xxxxxxxxxxxxx> Tested-by: Jason Liu <r64343@xxxxxxxxxxxxx> Jason Liu > > --- a/drivers/net/wireless/ath/ath6kl/hif.h > +++ b/drivers/net/wireless/ath/ath6kl/hif.h > @@ -197,9 +197,9 @@ struct hif_scatter_req { > /* bounce buffer for upper layers to copy to/from */ > u8 *virt_dma_buf; > > - struct hif_scatter_item scat_list[1]; > - > u32 scat_q_depth; > + > + struct hif_scatter_item scat_list[0]; > }; > > struct ath6kl_irq_proc_registers { > diff --git a/drivers/net/wireless/ath/ath6kl/sdio.c > b/drivers/net/wireless/ath/ath6kl/sdio.c > index 7126bdd..6bf15a3 100644 > --- a/drivers/net/wireless/ath/ath6kl/sdio.c > +++ b/drivers/net/wireless/ath/ath6kl/sdio.c > @@ -348,7 +348,7 @@ static int ath6kl_sdio_alloc_prep_scat_req(struct > ath6kl_sdio *ar_sdio, > int i, scat_req_sz, scat_list_sz, size; > u8 *virt_buf; > > - scat_list_sz = (n_scat_entry - 1) * sizeof(struct hif_scatter_item); > + scat_list_sz = n_scat_entry * sizeof(struct hif_scatter_item); > scat_req_sz = sizeof(*s_req) + scat_list_sz; > > if (!virt_scat) > > > -- > Kalle Valo -- To unsubscribe from this list: send the line "unsubscribe linux-wireless" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
