On Wed, Oct 08, 2014 at 12:50:28PM +0200, Michal Kazior wrote: > On 8 October 2014 12:33, Rajkumar Manoharan <rmanohar@xxxxxxxxxxxxxxxx> wrote: > > On Wed, Oct 08, 2014 at 11:45:38AM +0200, Michal Kazior wrote: > >> On 8 October 2014 11:16, Rajkumar Manoharan <rmanohar@xxxxxxxxxxxxxxxx> wrote: > >> > The commit "ath10k: workaround fw beaconing bug" is freeing > >> > DMA-coherent memory in irq context which is hitting BUG ON > >> > in ARM platforms. Fix this by moving dma_free out of spin > >> > lock. > >> > >> I hardly see how moving the freeing outside the spinlock is a fix. > >> > >> > >> > kernel BUG at mm/vmalloc.c:1512! > >> > Internal error: Oops - BUG: 0 [#1] PREEMPT SMP ARM > >> > CPU: 0 PID: 722 Comm: hostapd Not tainted 3.14.0 #3 > >> > task: dd58b840 ti: da6a6000 task.ti: da6a6000 > >> > PC is at vunmap+0x24/0x34 > >> > LR is at __arm_dma_free.isra.21+0x12c/0x190 > >> > [<c02a97d0>] (vunmap) from [<c021f81c>] (__arm_dma_free.isra.21+0x12c/0x190) > >> > [<c021f81c>] (__arm_dma_free.isra.21) from [<bf3b2440>] > >> > (ath10k_mac_vif_beacon_free+0xf4/0x100 [ath10k_core]) > >> > [<bf3b2440>] (ath10k_mac_vif_beacon_free [ath10k_core]) from [<bf3b2490>] > >> > (ath10k_remove_interface+0x44/0x1ec [ath10k_core]) > >> > [<bf3b2490>] (ath10k_remove_interface [ath10k_core]) from [<bf3352e4>] > >> > (ieee80211_add_virtual_monitor+0x9d8/0x9f0 [mac80211]) > >> > [<bf3352e4>] (ieee80211_add_virtual_monitor [mac80211]) from [<bf33530c>] > >> > (ieee80211_stop+0x10/0x18 [mac80211]) > >> > [<bf33530c>] (ieee80211_stop [mac80211]) from [<c040d144>] > >> > (__dev_close_many+0x9c/0xcc) > >> > >> 1. How can even ieee80211_add_virtual_monitor() call > >> ath10k_remove_interface()? Upstream ath10k doesn't advertise > >> IEEE80211_HW_WANT_MONITOR_VIF. This call trace is either invalid, > >> you're not using upstream ath10k and/or have custom patches applied to > >> ath10k. > >> > > This is the backtrace captured on panic and we are getting the same > > backtrace consistently. I confirmed that add_virtual_monitor is not > > called for ath10k as it is not advertising. ath10k_remove_interface is > > called for master mode. > > > >> 2. How can ieee80211_stop() be called from an interrupt context > >> anyway? ieee80211_stop() calls ieee80211_do_stop() which calls > >> ieee80211_roc_purge() which tries to get a hold of local->mtx. This > >> implies ieee80211_stop() isn't design to be run in an interrupt > >> context to begin with so I don't see why ath10k should even care if > >> ath10k_remove_interface() is called in an interrupt context at this > >> point. > >> > > in_interrupt is counting soft and hard irqs. ieee80211_stop is not > > called from interrupt context. In ath10k, by aquiring spin_lock in > > ath10k_mac_vif_beacon_free is increasing soft irq count. > > > > In ARM arch, __arm_dma_free is calling vunmap which might sleep. So it > > can not be called within spin_lock. > > Did you try using GFP_ATOMIC in the dma_alloc_coherent instead of > moving the spinlock? > Nope. The problem is while freeing dma memory not during allocation. dma_free_coherent won't take any GFP_* flags. > > > > > Similar to dma_alloc_coherent, dma_free_coherent can not be called under > > soft irq context. > > The call trace points to ath10k_mac_vif_beacon_free() which doesn't > use dma_free_coherent() so why are you blaming it for the BUG_ON? > I agree the calltrace is a bogus. ath10k_mac_vif_beacon_cleanup is calling dma_free_coherent. > If anything the offender should be dma_unmap_single() but the thing is > beacon_buf is always allocated for AP/IBSS now which means > dma_unmap_single() is never called. For non-AP/IBSS both arvif->beacon > and arvif->beacon_buf are always NULL so neither > dma_alloc/free_coherent nor dma_map/unmap_single are called. > Agree. We need one more check in ath10k_mac_vif_beacon_free. But here the problem is dma_free_coherent is being called from soft irq context which is not allowed (BUG_ON noted in ARM arch). After moving dma_free_coherent out of spinlock, the kernel BUG at mm/vmalloc.c:1512 is never hit. -Rajkumar -- 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
