Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754545AbbHDCUe (ORCPT ); Mon, 3 Aug 2015 22:20:34 -0400 Received: from mail1.windriver.com ([147.11.146.13]:47612 "EHLO mail1.windriver.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754499AbbHDCU3 (ORCPT ); Mon, 3 Aug 2015 22:20:29 -0400 Message-ID: <55C020CA.5070101@windriver.com> Date: Tue, 4 Aug 2015 10:17:46 +0800 From: fupan User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.7.0 MIME-Version: 1.0 To: CC: , , , , Subject: Re: [PATCH] usb: gadget: f_printer: fix the bug of deadlock caused by nested spinlock References: <1438600783-22333-1-git-send-email-fupan.li@windriver.com> <20150803144742.GB1498@saruman.tx.rr.com> In-Reply-To: <20150803144742.GB1498@saruman.tx.rr.com> Content-Type: text/plain; charset="windows-1252"; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4180 Lines: 99 On 08/03/2015 10:47 PM, Felipe Balbi wrote: > Hi, > > On Mon, Aug 03, 2015 at 07:19:43PM +0800, fupan.li@windriver.com wrote: >> From: fli >> >> Function printer_func_disable() has called spinlock on printer_dev->lock, >> and it'll call function chain of >> >> printer_reset_interface() >> | >> +---dwc3_gadget_ep_disable() >> | >> +---__dwc3_gadget_ep_disable() >> | >> +---dwc3_remove_requests() >> | >> +---dwc3_gadget_giveback() >> | >> +---rx_complete() >> >> in the protected block. >> >> However, rx_complete() in f_printer.c calls spinlock on printer_dev->lock again, >> which will cause system hang. >> >> The following steps can reproduce this hang: >> >> 1. Build the test program from Documentation/usb/gadget_printer.txt as g_printer >> 2. Plug in the USB device to a host(such as Ubuntu). >> 3. on the USB device system run: >> #modprobe g_printer.ko >> #./g_printer -read_data >> >> 4. Unplug the USB device from the host >> >> The system will hang later. >> >> In order to avoid this deadlock, moving the spinlock from printer_func_disable() into >> printer_reset_interface() and excluding the block of calling dwc3_gadget_ep_disable(), >> in which the critical resource will be protected by its spinlock in rx_complete(). >> >> This commit will fix the system hang with the following calltrace: >> >> INFO: rcu_preempt detected stalls on CPUs/tasks: { 3} (detected by 0, t=21006 jiffies, g=524, c=523, q=2) >> sending NMI to all CPUs: >> NMI backtrace for cpu 3 >> CPU: 3 PID: 718 Comm: irq/22-dwc3 Not tainted 3.10.38-ltsi-WR6.0.0.11_standard #2 >> Hardware name: Intel Corp. VALLEYVIEW B3 PLATFORM/NOTEBOOK, BIOS BYTICRB1.86C.0092.R32.1410021707 10/02/2014 >> task: f44f4c20 ti: f40f6000 task.ti: f40f6000 >> EIP: 0060:[] EFLAGS: 00000097 CPU: 3 >> EIP is at _raw_spin_lock_irqsave+0x35/0x40 >> EAX: 00000076 EBX: f80fad00 ECX: 00000076 EDX: 00000075 >> ESI: 00000096 EDI: ffffff94 EBP: f40f7e20 ESP: f40f7e18 >> DS: 007b ES: 007b FS: 00d8 GS: 0000 SS: 0068 >> CR0: 8005003b CR2: b77ac000 CR3: 01c30000 CR4: 001007f0 >> DR0: 00000000 DR1: 00000000 DR2: 00000000 DR3: 00000000 >> DR6: ffff0ff0 DR7: 00000400 >> Stack: >> f474a720 f80fad00 f40f7e3c f80f93cc c135d486 00000000 f474a720 f468fb00 >> f4bea894 f40f7e54 f7e35f19 ffffff00 f468fb00 f468fb24 00000086 f40f7e64 >> f7e36577 f468fb00 f4bea810 f40f7e74 f7e365a8 f468fb00 f4bea894 f40f7e9c >> Call Trace: >> [] rx_complete+0x1c/0xb0 [g_printer] >> [] ? vsnprintf+0x166/0x390 >> [] dwc3_gadget_giveback+0xc9/0xf0 [dwc3] >> [] dwc3_remove_requests+0x57/0x70 [dwc3] >> [] __dwc3_gadget_ep_disable+0x18/0x60 [dwc3] >> [] dwc3_gadget_ep_disable+0x89/0xf0 [dwc3] >> [] printer_reset_interface+0x31/0x50 [g_printer] >> [] printer_func_disable+0x20/0x30 [g_printer] >> [] composite_disconnect+0x4b/0x90 [libcomposite] >> [] dwc3_disconnect_gadget+0x38/0x43 [dwc3] >> [] dwc3_gadget_disconnect_interrupt+0x3e/0x5a [dwc3] >> [] dwc3_thread_interrupt+0x5c8/0x610 [dwc3] >> [] irq_thread_fn+0x18/0x30 >> [] irq_thread+0x100/0x130 >> [] ? irq_finalize_oneshot.part.29+0xb0/0xb0 >> [] ? wake_threads_waitq+0x40/0x40 >> [] ? irq_thread_dtor+0xb0/0xb0 >> [] kthread+0x94/0xa0 >> [] ret_from_kernel_thread+0x1b/0x28 >> [] ? kthread_create_on_node+0xc0/0xc0 >> >> Signed-off-by: fupan li > Thanks, out of curiosity, do you plan on sending a glue layer for > Windriver's DWC3 ? No, just this fix patch. Fupan > > cheers > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/