From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jeremy Fitzhardinge Subject: blktap lockdep hiccup Date: Tue, 07 Sep 2010 11:39:49 +1000 Message-ID: <4C8597E5.4070802@goop.org> References: <1282546470-5547-1-git-send-email-daniel.stodden@citrix.com> <1282546470-5547-2-git-send-email-daniel.stodden@citrix.com> <4C802934.2000305@goop.org> <1283468932.3092.3924.camel@ramone.somacoma.net> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1283468932.3092.3924.camel@ramone.somacoma.net> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xensource.com Errors-To: xen-devel-bounces@lists.xensource.com To: Daniel Stodden Cc: Xen , Tom Kopec List-Id: xen-devel@lists.xenproject.org On 09/03/2010 09:08 AM, Daniel Stodden wrote: > On Thu, 2010-09-02 at 18:46 -0400, Jeremy Fitzhardinge wrote: >> On 08/22/2010 11:54 PM, Daniel Stodden wrote: >>> Response processing doesn't really belong into hard irq context. >>> >>> Another potential problem this avoids is that switching interrupt cpu >>> affinity in Xen domains can presently lead to event loss, if >>> RING_FINAL_CHECK is run from hard irq context. >> I just got this warning from a 32-bit pv domain. I think it may relate >> to this change. The warning is > We clearly spin_lock_irqsave all through the blkif_do_interrupt frame. > > It follows that something underneath quite unconditionally chose to > reenable them again (?) > > Either: Can you add a bunch of similar WARN_ONs along that path? > > Or: This lock is quite coarse-grained. The lock only matters for queue > access, and we know irqs are reenabled, so no need for flags. In fact we > only need to spin_lock_irq around the __blk_end_ calls and > kick_pending_. > > But I don't immediately see what's to blame, so I'd be curious. I haven't got around to investigating this in more detail yet, but there's also this long-standing lockdep hiccup in blktap: Starting auto Xen domains: lurch alloc irq_desc for 1235 on node 0 alloc kstat_irqs on node 0 block tda: sector-size: 512 capacity: 614400 INFO: trying to register non-static key. the code is fine but needs lockdep annotation. turning off the locking correctness validator. Pid: 4266, comm: tapdisk2 Not tainted 2.6.32.21 #146 Call Trace: [] __lock_acquire+0x1df/0x16e5 [] ? xen_force_evtchn_callback+0xd/0xf [] ? check_events+0x12/0x20 [] ? apply_to_page_range+0x295/0x37d [] lock_acquire+0xcd/0xf1 [] ? apply_to_page_range+0x295/0x37d [] ? apply_to_page_range+0x195/0x37d [] _spin_lock+0x31/0x40 [] ? apply_to_page_range+0x295/0x37d [] apply_to_page_range+0x295/0x37d [] ? blktap_map_uaddr_fn+0x0/0x55 [] ? xen_make_pte+0x8a/0x8e [] blktap_device_process_request+0x43d/0x954 [] ? xen_force_evtchn_callback+0xd/0xf [] ? check_events+0x12/0x20 [] ? xen_force_evtchn_callback+0xd/0xf [] ? check_events+0x12/0x20 [] ? mark_held_locks+0x52/0x70 [] ? _spin_unlock_irq+0x30/0x3c [] ? trace_hardirqs_on_caller+0x125/0x150 [] blktap_device_run_queue+0x1c5/0x28f [] ? unbind_from_irq+0x18/0x198 [] ? check_events+0x12/0x20 [] blktap_ring_poll+0x7c/0xc7 [] do_select+0x387/0x584 [] ? do_select+0x0/0x584 [] ? __pollwait+0x0/0xcc [] ? pollwake+0x0/0x56 [] ? pollwake+0x0/0x56 [] ? pollwake+0x0/0x56 [] ? pollwake+0x0/0x56 [] ? __lock_acquire+0x16d6/0x16e5 [] ? xen_force_evtchn_callback+0xd/0xf [] ? check_events+0x12/0x20 [] ? xen_force_evtchn_callback+0xd/0xf [] ? check_events+0x12/0x20 [] ? xen_force_evtchn_callback+0xd/0xf [] core_sys_select+0x20c/0x2da [] ? core_sys_select+0x3e/0x2da [] ? check_events+0x12/0x20 [] ? xen_restore_fl_direct_end+0x0/0x1 [] ? kmem_cache_free+0x18e/0x1c8 [] ? sock_destroy_inode+0x19/0x1b [] ? destroy_inode+0x2f/0x44 [] ? pvclock_clocksource_read+0x4b/0xa2 [] ? xen_clocksource_read+0x21/0x23 [] ? xen_clocksource_get_cycles+0x9/0x16 [] ? ktime_get_ts+0xb2/0xbf [] sys_select+0x96/0xbe [] system_call_fastpath+0x16/0x1b block tdb: sector-size: 512 capacity: 20971520 block tdc: sector-size: 512 capacity: 146800640 block tdd: sector-size: 512 capacity: 188743680 J