On 2018-02-25 21:04:27 [-0500], Hook, Gary wrote: > On 2/23/2018 5:33 PM, Sebastian Andrzej Siewior wrote: > > I don't why we need take a single write lock and disable interrupts > > while setting up debugfs. This is what what happens when we try anyway: > > There is more than one CCP on some processors. The lock is intended to > serialize attempts to initialize the new directory, but a R/W lock isn't > required. And they are probed in parallel? Any you need disable interrupts while creating the debugfs folder? A mutex isn't enough? > My testing on an EPYC (8 CCPs) didn't expose this problem. May I ask what > hardware you used here? an EPYC, too. I have no idea how many CCPs were around but lspci -k printed that driver more than once. Try to enable lockdep and "sleeping while atomic". But I did provide you a complete backtrace, look: > > |ccp 0000:03:00.2: enabling device (0000 -> 0002) > > |BUG: sleeping function called from invalid context at kernel/locking/rwsem.c:69 > > |in_atomic(): 1, irqs_disabled(): 1, pid: 3, name: kworker/0:0 > > |irq event stamp: 17150 > > |hardirqs last enabled at (17149): [<0000000097a18c49>] restore_regs_and_return_to_kernel+0x0/0x23 > > |hardirqs last disabled at (17150): [<000000000773b3a9>] _raw_write_lock_irqsave+0x1b/0x50 > > |softirqs last enabled at (17148): [<0000000064d56155>] __do_softirq+0x3b8/0x4c1 > > |softirqs last disabled at (17125): [<0000000092633c18>] irq_exit+0xb1/0xc0 > > |CPU: 0 PID: 3 Comm: kworker/0:0 Not tainted 4.16.0-rc2+ #30 > > |Workqueue: events work_for_cpu_fn > > |Call Trace: > > | dump_stack+0x7d/0xb6 > > | ___might_sleep+0x1eb/0x250 > > | down_write+0x17/0x60 > > | start_creating+0x4c/0xe0 > > | debugfs_create_dir+0x9/0x100 > > | ccp5_debugfs_setup+0x191/0x1b0 > > | ccp5_init+0x8a7/0x8c0 > > | ccp_dev_init+0xb8/0xe0 > > | sp_init+0x6c/0x90 > > | sp_pci_probe+0x26e/0x590 > > | local_pci_probe+0x3f/0x90 > > | work_for_cpu_fn+0x11/0x20 > > | process_one_work+0x1ff/0x650 > > | worker_thread+0x1d4/0x3a0 > > | kthread+0xfe/0x130 > > | ret_from_fork+0x27/0x50 Sebastian
