>> Bin Liu <b-liu@xxxxxx> writes:
>> > On Wed, May 25, 2016 at 02:18:34PM -0500, Bin Liu wrote:
>> >> [ 40.467381] =============================================
>> >> [ 40.473013] [ INFO: possible recursive locking detected ]
>> >> [ 40.478651] 4.6.0-08691-g7f3db9a #37 Not tainted
>> >> [ 40.483466] ---------------------------------------------
>> >> [ 40.489098] usb/733 is trying to acquire lock:
>> >> [ 40.493734] (&(&dev->lock)->rlock){-.....}, at: [<bf129288>] ep0_complete+0x18/0xdc [gadgetfs]
>> >> [ 40.502882]
>> >> [ 40.502882] but task is already holding lock:
>> >> [ 40.508967] (&(&dev->lock)->rlock){-.....}, at: [<bf12a420>] ep0_read+0x20/0x5e0 [gadgetfs]
>> >> [ 40.517811]
>> >> [ 40.517811] other info that might help us debug this:
>> >> [ 40.524623] Possible unsafe locking scenario:
>> >> [ 40.524623]
>> >> [ 40.530798] CPU0
>> >> [ 40.533346] ----
>> >> [ 40.535894] lock(&(&dev->lock)->rlock);
>> >> [ 40.540088] lock(&(&dev->lock)->rlock);
>> >> [ 40.544284]
>> >> [ 40.544284] *** DEADLOCK ***
>> >> [ 40.544284]
>> >> [ 40.550461] May be due to missing lock nesting notation
>> >> [ 40.550461]
>> >> [ 40.557544] 2 locks held by usb/733:
>> >> [ 40.561271] #0: (&f->f_pos_lock){+.+.+.}, at: [<c02a6114>] __fdget_pos+0x40/0x48
>> >> [ 40.569219] #1: (&(&dev->lock)->rlock){-.....}, at: [<bf12a420>] ep0_read+0x20/0x5e0 [gadgetfs]
>> >> [ 40.578523]
>> >> [ 40.578523] stack backtrace:
>> >> [ 40.583075] CPU: 0 PID: 733 Comm: usb Not tainted 4.6.0-08691-g7f3db9a #37
>> >> [ 40.590246] Hardware name: Generic AM33XX (Flattened Device Tree)
>> >> [ 40.596625] [<c010ffbc>] (unwind_backtrace) from [<c010c1bc>] (show_stack+0x10/0x14)
>> >> [ 40.604718] [<c010c1bc>] (show_stack) from [<c04207fc>] (dump_stack+0xb0/0xe4)
>> >> [ 40.612267] [<c04207fc>] (dump_stack) from [<c01886ec>] (__lock_acquire+0xf68/0x1994)
>> >> [ 40.620440] [<c01886ec>] (__lock_acquire) from [<c0189528>] (lock_acquire+0xd8/0x238)
>> >> [ 40.628621] [<c0189528>] (lock_acquire) from [<c06ad6b4>] (_raw_spin_lock_irqsave+0x38/0x4c)
>> >> [ 40.637440] [<c06ad6b4>] (_raw_spin_lock_irqsave) from [<bf129288>] (ep0_complete+0x18/0xdc [gadgetfs])
>> >> [ 40.647339] [<bf129288>] (ep0_complete [gadgetfs]) from [<bf10a728>] (musb_g_giveback+0x118/0x1b0 [musb_hdrc])
>> >> [ 40.657842] [<bf10a728>] (musb_g_giveback [musb_hdrc]) from [<bf108768>] (musb_g_ep0_queue+0x16c/0x188 [musb_hdrc])
>> >> [ 40.668772] [<bf108768>] (musb_g_ep0_queue [musb_hdrc]) from [<bf12a944>] (ep0_read+0x544/0x5e0 [gadgetfs])
>> >> [ 40.678963] [<bf12a944>] (ep0_read [gadgetfs]) from [<c0284470>] (__vfs_read+0x20/0x110)
>> >> [ 40.687414] [<c0284470>] (__vfs_read) from [<c0285324>] (vfs_read+0x88/0x114)
>> >> [ 40.694864] [<c0285324>] (vfs_read) from [<c0286150>] (SyS_read+0x44/0x9c)
>> >> [ 40.702051] [<c0286150>] (SyS_read) from [<c0107820>] (ret_fast_syscall+0x0/0x1c)
>> >>
>> >> Cc: <stable@xxxxxxxxxxxxxxx> # v3.16+
>> >> Signed-off-by: Bin Liu <b-liu@xxxxxx>
>> >> ---
>> >> v2:
>> >> - lock protects setup_req(), only unlock for usb_ep_queue()
>> >> - use GFP_KERNEL in usb_ep_queue()
>> >> - fix the same in two places in gadgetfs_setup() too
>> >
>> > Never mind. Sent the patch too soon. It gives the following problem.
>> >
>> > [ 179.810367] WARNING: CPU: 0 PID: 0 at kernel/locking/lockdep.c:2724
>> > _raw_spin_unlock_irq+0x24/0x2c
>> > [ 179.819719] DEBUG_LOCKS_WARN_ON(current->hardirq_context)
>>
>> thanks for letting us know. I'm dropping this from my queue. Please
>> resend final patch once you have it ;-)
>
> It turned out to be a very easy fix ;)
>
> I have v3 ready, but checkpatch.pl complains the followings. I don't
> think this patch should fix them, since the whole driver is coded like
> that. Any comments?
Let's fix it with a follow-up patch. Can you do that one too, btw? I can
do it, if you don't wanna deal with that; but I'm also open to receiving
free patches heh
--
balbi
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