From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stephen Warren Subject: Re: Reboot/shutdown failure due to "USB: EHCI: work around silicon bug in Intel's EHCI" Date: Tue, 19 Mar 2013 16:48:12 -0600 Message-ID: <5148EB2C.1080402@wwwdotorg.org> References: Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Sender: linux-usb-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Alan Stern Cc: "linux-tegra-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , USB list , Greg Kroah-Hartman List-Id: linux-tegra@vger.kernel.org On 03/19/2013 02:07 PM, Alan Stern wrote: > On Tue, 19 Mar 2013, Stephen Warren wrote: > >> Yes, sysrq seems to work over the serial console:-) >> >>> * Will now restart >>> >>> *** break sent *** >>> [ 180.765213] SysRq : Show Blocked State >>> [ 180.768963] task PC stack pid father >>> [ 180.774182] khubd D c0517678 0 21 2 0x00000000 >>> [ 180.780559] [] (__schedule+0x348/0x6dc) from [] (usb_kill_urb+0x88/0xd4) >>> [ 180.788984] [] (usb_kill_urb+0x88/0xd4) from [] (usb_start_wait_urb+0xa4/0x13c) >>> [ 180.798012] [] (usb_start_wait_urb+0xa4/0x13c) from [] (usb_control_msg+0x98/0xcc) >>> [ 180.807301] [] (usb_control_msg+0x98/0xcc) from [] (hub_port_init+0x5e0/0x9d0) >>> [ 180.816242] [] (hub_port_init+0x5e0/0x9d0) from [] (hub_port_connect_change+0x1f4/0x970) >>> [ 180.826050] [] (hub_port_connect_change+0x1f4/0x970) from [] (hub_events+0x340/0x8c4) >>> [ 180.835598] [] (hub_events+0x340/0x8c4) from [] (hub_thread+0x28/0x1b8) >>> [ 180.843941] [] (hub_thread+0x28/0x1b8) from [] (kthread+0xa4/0xb0) > >> I assume you only want the back-traces, not the reset of the sysrq spew? > > Yes. It looks like khubd is your problem. > >> BTW, I have also occasionally noticed some either hung task or RCU spew >> related to usb_kill_urb at other times (i.e. when not rebooting), IIRC >> (which I may not; I may be remembering what happens if I just leave the >> reboot hung for a few minutes, as shown below): >> >>> [ 240.670335] INFO: task khubd:21 blocked for more than 120 seconds. >>> [ 240.676516] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. >>> [ 240.684336] khubd D c0517678 0 21 2 0x00000000 > > Right. It's another symptom of the same thing. This problem occurs > well before shutdown -- something is causing khubd to hang and that > messes up everything else. > > A dmesg log with CONFIG_USB_DEBUG enabled would be helpful. We ought > to be able to tell where khubd is getting stuck. Hmmm. Enabling CONFIG_USB_DEBUG appears to mask the problem. I assume this is some kind of timing/race condition, unless there's some code with required side-effects hiding under ifdef CONFIG_USB_DEBUG somehow? -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html