From mboxrd@z Thu Jan 1 00:00:00 1970 From: hch@infradead.org (Christoph Hellwig) Date: Fri, 25 Sep 2015 15:11:37 -0700 Subject: [PATCH 2/7] nvme: switch AEN processing to use blk_execute_rq_nowait In-Reply-To: References: <1442860853-26447-1-git-send-email-hch@lst.de> <1442860853-26447-3-git-send-email-hch@lst.de> <20150924133850.GA6350@lst.de> Message-ID: <20150925221137.GA17965@infradead.org> On Thu, Sep 24, 2015@01:51:33PM +0000, Keith Busch wrote: > >Yigal, is there a nice easy way to trigger the CPU hotplug migration > >through sysfs or another userspace interface? I think I can solve > >this without freeing the AEN early with a little more thought. > > To take a cpu offline and trigger a removal: > > echo 0 > /sys/devices/system/cpu/cpu1/online That is already broken in 4.3-rc2 unfortunately: [ 149.094678] Failed to recover vector for irq 104 [ 149.144128] BUG: unable to handle kernel NULL pointer dereference at 00000000 [ 149.152022] IP: [] blk_mq_map_swqueue+0xf1/0x260 [ 149.158239] PGD c9d59067 PUD c78ac067 PMD 0 [ 149.162556] Oops: 0002 [#1] SMP DEBUG_PAGEALLOC [ 149.167222] Modules linked in: nfsd auth_rpcgss oid_registry nfs_acl nfs loc2 [ 149.249367] CPU: 7 PID: 1192 Comm: bash Tainted: G I 4.3.0-rc2+9 [ 149.256788] Hardware name: Dell Inc. PowerEdge R710/00NH4P, BIOS 3.0.0 01/311 [ 149.264295] task: ffff8806115f8040 ti: ffff880613124000 task.ti: ffff88061310 [ 149.271805] RIP: 0010:[] [] blk_mq_map_0 [ 149.280461] RSP: 0018:ffff880613127c28 EFLAGS: 00010282 [ 149.285789] RAX: ffff880604b9ac00 RBX: ffffe8fcf6f06a80 RCX: ffff8803234edf00 [ 149.292946] RDX: 0000000000000000 RSI: 0000000000000009 RDI: ffff8806049c12e0 [ 149.300103] RBP: ffff880613127c60 R08: 0000000000000007 R09: 0000000000000000 [ 149.307261] R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000009 [ 149.314419] R13: ffff8806049c12e0 R14: ffff880607fcdc20 R15: ffffffff81d2ad00 [ 149.321577] FS: 00007fa17ee79700(0000) GS:ffff880323ac0000(0000) knlGS:00000 [ 149.329694] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 149.335457] CR2: 0000000000000080 CR3: 00000000caf51000 CR4: 00000000000006e0 [ 149.342616] Stack: [ 149.344633] 0000000000000000 0000000000000000 ffff8806049c12e0 ffffffff81cc0 [ 149.352101] ffffffff81cfaa00 0000000000000000 0000000000000001 ffff880613120 [ 149.359567] ffffffff81320227 ffffffff81cc4740 00000000ffffffe1 ffff880613120 [ 149.367034] Call Trace: [ 149.369491] [] blk_mq_queue_reinit_notify+0x137/0x1d0 [ 149.376216] [] notifier_call_chain+0x5d/0x80 [ 149.382156] [] __raw_notifier_call_chain+0xe/0x10 [ 149.388533] [] cpu_notify+0x23/0x40 [ 149.393687] [] cpu_notify_nofail+0xe/0x20 [ 149.399365] [] _cpu_down+0x1b5/0x2b0 [ 149.404607] [] cpu_down+0x36/0x50 [ 149.409589] [] cpu_subsys_offline+0x14/0x20 [ 149.415443] [] device_offline+0x88/0xb0 [ 149.420947] [] online_store+0x3d/0x80 [ 149.426277] [] dev_attr_store+0x18/0x30 [ 149.431782] [] sysfs_kf_write+0x45/0x60 [ 149.437286] [] kernfs_fop_write+0x141/0x190 [ 149.443140] [] __vfs_write+0x28/0xe0 [ 149.448385] [] ? percpu_down_read+0x5f/0xa0 [ 149.455461] [] ? __sb_start_write+0xf1/0x110 [ 149.462610] [] ? __sb_start_write+0xf1/0x110 [ 149.469747] [] vfs_write+0xa9/0x190 [ 149.476074] [] ? __fget_light+0x66/0x90 [ 149.482726] [] SyS_write+0x49/0xa0 [ 149.488935] [] entry_SYSCALL_64_fastpath+0x16/0x7a