On 05/03/15 10:49, Laurent Pinchart wrote:
Hi Sudeep, Thank you for the patch. On Wednesday 04 March 2015 17:07:57 Sudeep Holla wrote:Use spin_{un,}lock_irq{save,restore} in isp1760_udc_{start,stop} to prevent following potentially deadlock scenario between isp1760_udc_{start,stop} and isp1760_udc_irq : ================================= [ INFO: inconsistent lock state ] 4.0.0-rc2-00004-gf7bb2ef60173 #51 Not tainted --------------------------------- inconsistent {HARDIRQ-ON-W} -> {IN-HARDIRQ-W} usage. in:imklog/2118 [HC1[1]:SC0[0]:HE0:SE1] takes: (&(&udc->lock)->rlock){?.+...}, at: [<c0397a93>] isp1760_udc_irq+0x367/0x9dc {HARDIRQ-ON-W} state was registered at: [<c05135b3>] _raw_spin_lock+0x23/0x30 [<c0396b87>] isp1760_udc_start+0x23/0xf8 [<c039dc21>] udc_bind_to_driver+0x71/0xb0 [<c039de4f>] usb_gadget_probe_driver+0x53/0x9c [<bf80d0df>] usb_composite_probe+0x8a/0xa4 [libcomposite] [<bf8311a7>] 0xbf8311a7 [<c00088c5>] do_one_initcall+0x8d/0x17c [<c050b92d>] do_init_module+0x49/0x148 [<c0087323>] load_module+0xb7f/0xbc4 [<c0087471>] SyS_finit_module+0x51/0x74 [<c000d8c1>] ret_fast_syscall+0x1/0x68 irq event stamp: 4966 hardirqs last enabled at (4965): [<c05137df>] _raw_spin_unlock_irq+0x1f/0x24 hardirqs last disabled at (4966): [<c00110b3>] __irq_svc+0x33/0x64 softirqs last enabled at (4458): [<c0023475>] __do_softirq+0x23d/0x2d0 softirqs last disabled at (4389): [<c002380b>] irq_exit+0xef/0x15c other info that might help us debug this: Possible unsafe locking scenario: CPU0 ---- lock(&(&udc->lock)->rlock); <Interrupt> lock(&(&udc->lock)->rlock); *** DEADLOCK *** 1 lock held by in:imklog/2118: #0: (&f->f_pos_lock){+.+.+.}, at: [<c010a101>] __fdget_pos+0x31/0x34 Signed-off-by: Sudeep Holla <sudeep.holla@xxxxxxx> Cc: Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx> Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> Cc: Felipe Balbi <balbi@xxxxxx> --- drivers/usb/isp1760/isp1760-udc.c | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-) diff --git a/drivers/usb/isp1760/isp1760-udc.c b/drivers/usb/isp1760/isp1760-udc.c index 6d618b3fab07..fbfbd59aae64 100644 --- a/drivers/usb/isp1760/isp1760-udc.c +++ b/drivers/usb/isp1760/isp1760-udc.c @@ -1191,6 +1191,7 @@ static int isp1760_udc_start(struct usb_gadget *gadget, struct usb_gadget_driver *driver) { struct isp1760_udc *udc = gadget_to_udc(gadget); + unsigned long flags; /* The hardware doesn't support low speed. */ if (driver->max_speed < USB_SPEED_FULL) { @@ -1198,7 +1199,7 @@ static int isp1760_udc_start(struct usb_gadget *gadget, return -EINVAL; } - spin_lock(&udc->lock); + spin_lock_irqsave(&udc->lock, flags);Strictly speaking spin_lock_irq() should be enough given that udc_start and udc_stop are called with interrupts enabled, but I suppose it doesn't hurt to be safe. I'll let you go with your preference. For both options,
I agree, even I had similar thoughts but just played safe :)
Acked-by: Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx>
Thanks. -- Regars, Sudeep -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
