From f3bdf34465307fc3f6967a9202a921e11505b2e6 Mon Sep 17 00:00:00 2001 From: Mike Marciniszyn Date: Fri, 17 May 2013 12:40:32 +0000 Subject: [PATCH] IB/qib: Fix lockdep splat in qib_alloc_lkey() The following backtrace is reported with CONFIG_PROVE_RCU: drivers/infiniband/hw/qib/qib_keys.c:64 suspicious rcu_dereference_check() usage! other info that might help us debug this: rcu_scheduler_active = 1, debug_locks = 1 4 locks held by kworker/0:1/56: #0: (events){.+.+.+}, at: [] process_one_work+0x165/0x4a0 #1: ((&wfc.work)){+.+.+.}, at: [] process_one_work+0x165/0x4a0 #2: (device_mutex){+.+.+.}, at: [] ib_register_device+0x38/0x220 [ib_core] #3: (&(&dev->lk_table.lock)->rlock){......}, at: [] qib_alloc_lkey+0x3c/0x1b0 [ib_qib] stack backtrace: Pid: 56, comm: kworker/0:1 Not tainted 3.10.0-rc1+ #6 Call Trace: [] lockdep_rcu_suspicious+0xe5/0x130 [] qib_alloc_lkey+0x101/0x1b0 [ib_qib] [] qib_get_dma_mr+0xa6/0xd0 [ib_qib] [] ib_get_dma_mr+0x1a/0x50 [ib_core] [] ib_mad_port_open+0x12c/0x390 [ib_mad] [] ? trace_hardirqs_on_caller+0x105/0x190 [] ib_mad_init_device+0x52/0x110 [ib_mad] [] ? sl2vl_attr_show+0x30/0x30 [ib_qib] [] ib_register_device+0x1a9/0x220 [ib_core] [] qib_register_ib_device+0x735/0xa40 [ib_qib] [] ? mod_timer+0x118/0x220 [] qib_init_one+0x1e5/0x400 [ib_qib] [] local_pci_probe+0x4e/0x90 [] work_for_cpu_fn+0x18/0x30 [] process_one_work+0x1d6/0x4a0 [] ? process_one_work+0x165/0x4a0 [] worker_thread+0x119/0x370 [] ? manage_workers+0x180/0x180 [] kthread+0xee/0x100 [] ? __init_kthread_worker+0x70/0x70 [] ret_from_fork+0x7c/0xb0 [] ? __init_kthread_worker+0x70/0x70 Per Documentation/RCU/lockdep-splat.txt, the code now uses rcu_access_pointer() vs. rcu_dereference(). Reported-by: Jay Fenlason Reviewed-by: Dean Luick Signed-off-by: Mike Marciniszyn Signed-off-by: Roland Dreier --- drivers/infiniband/hw/qib/qib_keys.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/infiniband/hw/qib/qib_keys.c b/drivers/infiniband/hw/qib/qib_keys.c index 81c7b73695d2..3b9afccaaade 100644 --- a/drivers/infiniband/hw/qib/qib_keys.c +++ b/drivers/infiniband/hw/qib/qib_keys.c @@ -61,7 +61,7 @@ int qib_alloc_lkey(struct qib_mregion *mr, int dma_region) if (dma_region) { struct qib_mregion *tmr; - tmr = rcu_dereference(dev->dma_mr); + tmr = rcu_access_pointer(dev->dma_mr); if (!tmr) { qib_get_mr(mr); rcu_assign_pointer(dev->dma_mr, mr);