diff options
| author | wenlin.kang | 2014-01-08 14:22:11 +0800 |
|---|---|---|
| committer | Felipe Balbi | 2014-02-18 10:52:54 -0600 |
| commit | 2c2b04253bfc7ac67a2ab71a6e771cd42e9418fe (patch) | |
| tree | 7e4b15745ee49335f1975ff3a5b9736e9e6afd64 | |
| parent | 236064c253581367a62d67083a620318670683d0 (diff) | |
usb: gadget: printer: fix possible deadlock
The problem occurs in follow path.
printer_read()
|
+---setup_rx_reqs()
|
+---usb_ep_queue()
|
+---...
|
+---rx_complete()
Although it is clear from code, we can't get it normally.
only when we enable some spin_lock debug config option, we can find it.
eg:
BUG: spinlock lockup on CPU#0, g_printer_test_/584
lock: bf05e158, .magic: dead4ead, .owner: g_printer_test_/584, .owner_cpu: 0
[<c0016e1c>] (unwind_backtrace+0x0/0x104) from [<c067aef8>] (dump_stack+0x20/0x24)
[<c067aef8>] (dump_stack+0x20/0x24) from [<c0680bec>] (spin_dump+0x8c/0x94)
[<c0680bec>] (spin_dump+0x8c/0x94) from [<c039071c>] (do_raw_spin_lock+0x128/0x154)
[<c039071c>] (do_raw_spin_lock+0x128/0x154) from [<c0685618>] (_raw_spin_lock_irqsave+0x64/0x70)
[<c0685618>] (_raw_spin_lock_irqsave+0x64/0x70) from [<bf05b4e8>] (rx_complete+0x54/0x10c [g_printer])
[<bf05b4e8>] (rx_complete+0x54/0x10c [g_printer]) from [<c0480478>] (musb_g_giveback+0x78/0x88)
[<c0480478>] (musb_g_giveback+0x78/0x88) from [<c048060c>] (rxstate+0xa0/0x10c)
[<c048060c>] (rxstate+0xa0/0x10c) from [<c0480d50>] (musb_ep_restart+0x44/0x70)
[<c0480d50>] (musb_ep_restart+0x44/0x70) from [<c0480fe4>] (musb_gadget_queue+0xe8/0xf8)
[<c0480fe4>] (musb_gadget_queue+0xe8/0xf8) from [<bf05b2b0>] (setup_rx_reqs+0xa4/0x178 [g_printer])
[<bf05b2b0>] (setup_rx_reqs+0xa4/0x178 [g_printer]) from [<bf05bb58>] (printer_read+0x9c/0x3f4 [g_printer])
[<bf05bb58>] (printer_read+0x9c/0x3f4 [g_printer]) from [<c01387f0>] (vfs_read+0xb4/0x144)
[<c01387f0>] (vfs_read+0xb4/0x144) from [<c01388d0>] (sys_read+0x50/0x124)
[<c01388d0>] (sys_read+0x50/0x124) from [<c000e900>] (ret_fast_syscall+0x0/0x3c)
The root cause is that we use the same lock two time in a path, so to avoid
the deadlock, we need to unlock in setup_rx_reqs(), and only unlock.
Signed-off-by: wenlin.kang <wenlin.kang@windriver.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>
| -rw-r--r-- | drivers/usb/gadget/printer.c | 3 |
1 files changed, 3 insertions, 0 deletions
diff --git a/drivers/usb/gadget/printer.c b/drivers/usb/gadget/printer.c index 92b55bdda566..96ffdac330b5 100644 --- a/drivers/usb/gadget/printer.c +++ b/drivers/usb/gadget/printer.c @@ -427,7 +427,10 @@ setup_rx_reqs(struct printer_dev *dev) req->length = USB_BUFSIZE; req->complete = rx_complete; + /* here, we unlock, and only unlock, to avoid deadlock. */ + spin_unlock(&dev->lock); error = usb_ep_queue(dev->out_ep, req, GFP_ATOMIC); + spin_lock(&dev->lock); if (error) { DBG(dev, "rx submit --> %d\n", error); list_add(&req->list, &dev->rx_reqs); |