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This addresses 3 separate problems: 1. When using NVME over Fabrics we may end up sending IP packets in interrupt context, we should defer this work to a tasklet. [ 50.939957] WARNING: CPU: 3 PID: 0 at kernel/softirq.c:161 __local_bh_enable_ip+0x1f/0xa0 [ 50.942602] CPU: 3 PID: 0 Comm: swapper/3 Kdump: loaded Tainted: G W 4.17.0-rc3-ARCH+ #104 [ 50.945466] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.11.0-20171110_100015-anatol 04/01/2014 [ 50.948163] RIP: 0010:__local_bh_enable_ip+0x1f/0xa0 [ 50.949631] RSP: 0018:ffff88009c183900 EFLAGS: 00010006 [ 50.951029] RAX: 0000000080010403 RBX: 0000000000000200 RCX: 0000000000000001 [ 50.952636] RDX: 0000000000000000 RSI: 0000000000000200 RDI: ffffffff817e04ec [ 50.954278] RBP: ffff88009c183910 R08: 0000000000000001 R09: 0000000000000614 [ 50.956000] R10: ffffea00021d5500 R11: 0000000000000001 R12: ffffffff817e04ec [ 50.957779] R13: 0000000000000000 R14: ffff88009566f400 R15: ffff8800956c7000 [ 50.959402] FS: 0000000000000000(0000) GS:ffff88009c180000(0000) knlGS:0000000000000000 [ 50.961552] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 50.963798] CR2: 000055c4ec0ccac0 CR3: 0000000002209001 CR4: 00000000000606e0 [ 50.966121] Call Trace: [ 50.966845] <IRQ> [ 50.967497] __dev_queue_xmit+0x62d/0x690 [ 50.968722] dev_queue_xmit+0x10/0x20 [ 50.969894] neigh_resolve_output+0x173/0x190 [ 50.971244] ip_finish_output2+0x2b8/0x370 [ 50.972527] ip_finish_output+0x1d2/0x220 [ 50.973785] ? ip_finish_output+0x1d2/0x220 [ 50.975010] ip_output+0xd4/0x100 [ 50.975903] ip_local_out+0x3b/0x50 [ 50.976823] rxe_send+0x74/0x120 [ 50.977702] rxe_requester+0xe3b/0x10b0 [ 50.978881] ? ip_local_deliver_finish+0xd1/0xe0 [ 50.980260] rxe_do_task+0x85/0x100 [ 50.981386] rxe_run_task+0x2f/0x40 [ 50.982470] rxe_post_send+0x51a/0x550 [ 50.983591] nvmet_rdma_queue_response+0x10a/0x170 [ 50.985024] __nvmet_req_complete+0x95/0xa0 [ 50.986287] nvmet_req_complete+0x15/0x60 [ 50.987469] nvmet_bio_done+0x2d/0x40 [ 50.988564] bio_endio+0x12c/0x140 [ 50.989654] blk_update_request+0x185/0x2a0 [ 50.990947] blk_mq_end_request+0x1e/0x80 [ 50.991997] nvme_complete_rq+0x1cc/0x1e0 [ 50.993171] nvme_pci_complete_rq+0x117/0x120 [ 50.994355] __blk_mq_complete_request+0x15e/0x180 [ 50.995988] blk_mq_complete_request+0x6f/0xa0 [ 50.997304] nvme_process_cq+0xe0/0x1b0 [ 50.998494] nvme_irq+0x28/0x50 [ 50.999572] __handle_irq_event_percpu+0xa2/0x1c0 [ 51.000986] handle_irq_event_percpu+0x32/0x80 [ 51.002356] handle_irq_event+0x3c/0x60 [ 51.003463] handle_edge_irq+0x1c9/0x200 [ 51.004473] handle_irq+0x23/0x30 [ 51.005363] do_IRQ+0x46/0xd0 [ 51.006182] common_interrupt+0xf/0xf [ 51.007129] </IRQ> 2. Work must always be offloaded to tasklet for rxe_post_send_kernel() when using NVMEoF in order to solve lock ordering between neigh->ha_lock seqlock and the nvme queue lock: [ 77.833783] Possible interrupt unsafe locking scenario: [ 77.833783] [ 77.835831] CPU0 CPU1 [ 77.837129] ---- ---- [ 77.838313] lock(&(&n->ha_lock)->seqcount); [ 77.839550] local_irq_disable(); [ 77.841377] lock(&(&nvmeq->q_lock)->rlock); [ 77.843222] lock(&(&n->ha_lock)->seqcount); [ 77.845178] <Interrupt> [ 77.846298] lock(&(&nvmeq->q_lock)->rlock); [ 77.847986] [ 77.847986] *** DEADLOCK *** 3. Same goes for the lock ordering between sch->q.lock and nvme queue lock: [ 47.634271] Possible interrupt unsafe locking scenario: [ 47.634271] [ 47.636452] CPU0 CPU1 [ 47.637861] ---- ---- [ 47.639285] lock(&(&sch->q.lock)->rlock); [ 47.640654] local_irq_disable(); [ 47.642451] lock(&(&nvmeq->q_lock)->rlock); [ 47.644521] lock(&(&sch->q.lock)->rlock); [ 47.646480] <Interrupt> [ 47.647263] lock(&(&nvmeq->q_lock)->rlock); [ 47.648492] [ 47.648492] *** DEADLOCK *** Using NVMEoF after this patch seems to finally be stable, without it, rxe eventually deadlocks the whole system and causes RCU stalls. Signed-off-by: Alexandru Moise <00moses.alexander00@gmail.com> Reviewed-by: Zhu Yanjun <yanjun.zhu@oracle.com> Signed-off-by: Doug Ledford <dledford@redhat.com>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
See Documentation/00-INDEX for a list of what is contained in each file.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.