mirror of
https://github.com/hardkernel/linux.git
synced 2026-04-04 04:03:04 +09:00
812e484133
commit ed62ca2f4f upstream.
While running reboot tests w/ a specific set of USB devices (and
slub_debug enabled), I found that once every few hours my device would
be crashed with a stack that looked like this:
[ 14.012445] BUG: spinlock bad magic on CPU#0, modprobe/2091
[ 14.012460] lock: 0xffffffc0cb055978, .magic: ffffffc0, .owner: cryption contexts: %lu/%lu
[ 14.012460] /1025536097, .owner_cpu: 0
[ 14.012466] CPU: 0 PID: 2091 Comm: modprobe Not tainted 4.4.79 #352
[ 14.012468] Hardware name: Google Kevin (DT)
[ 14.012471] Call trace:
[ 14.012483] [<....>] dump_backtrace+0x0/0x160
[ 14.012487] [<....>] show_stack+0x20/0x28
[ 14.012494] [<....>] dump_stack+0xb4/0xf0
[ 14.012500] [<....>] spin_dump+0x8c/0x98
[ 14.012504] [<....>] spin_bug+0x30/0x3c
[ 14.012508] [<....>] do_raw_spin_lock+0x40/0x164
[ 14.012515] [<....>] _raw_spin_lock_irqsave+0x64/0x74
[ 14.012521] [<....>] __wake_up+0x2c/0x60
[ 14.012528] [<....>] async_completed+0x2d0/0x300
[ 14.012534] [<....>] __usb_hcd_giveback_urb+0xc4/0x138
[ 14.012538] [<....>] usb_hcd_giveback_urb+0x54/0xf0
[ 14.012544] [<....>] xhci_irq+0x1314/0x1348
[ 14.012548] [<....>] usb_hcd_irq+0x40/0x50
[ 14.012553] [<....>] handle_irq_event_percpu+0x1b4/0x3f0
[ 14.012556] [<....>] handle_irq_event+0x4c/0x7c
[ 14.012561] [<....>] handle_fasteoi_irq+0x158/0x1c8
[ 14.012564] [<....>] generic_handle_irq+0x30/0x44
[ 14.012568] [<....>] __handle_domain_irq+0x90/0xbc
[ 14.012572] [<....>] gic_handle_irq+0xcc/0x18c
Investigation using kgdb() found that the wait queue that was passed
into wake_up() had been freed (it was filled with slub_debug poison).
I analyzed and instrumented the code and reproduced. My current
belief is that this is happening:
1. async_completed() is called (from IRQ). Moves "as" onto the
completed list.
2. On another CPU, proc_reapurbnonblock_compat() calls
async_getcompleted(). Blocks on spinlock.
3. async_completed() releases the lock; keeps running; gets blocked
midway through wake_up().
4. proc_reapurbnonblock_compat() => async_getcompleted() gets the
lock; removes "as" from completed list and frees it.
5. usbdev_release() is called. Frees "ps".
6. async_completed() finally continues running wake_up(). ...but
wake_up() has a pointer to the freed "ps".
The instrumentation that led me to believe this was based on adding
some trace_printk() calls in a select few functions and then using
kdb's "ftdump" at crash time. The trace follows (NOTE: in the trace
below I cheated a little bit and added a udelay(1000) in
async_completed() after releasing the spinlock because I wanted it to
trigger quicker):
<...>-2104 0d.h2 13759034us!: async_completed at start: as=ffffffc0cc638200
mtpd-2055 3.... 13759356us : async_getcompleted before spin_lock_irqsave
mtpd-2055 3d..1 13759362us : async_getcompleted after list_del_init: as=ffffffc0cc638200
mtpd-2055 3.... 13759371us+: proc_reapurbnonblock_compat: free_async(ffffffc0cc638200)
mtpd-2055 3.... 13759422us+: async_getcompleted before spin_lock_irqsave
mtpd-2055 3.... 13759479us : usbdev_release at start: ps=ffffffc0cc042080
mtpd-2055 3.... 13759487us : async_getcompleted before spin_lock_irqsave
mtpd-2055 3.... 13759497us!: usbdev_release after kfree(ps): ps=ffffffc0cc042080
<...>-2104 0d.h2 13760294us : async_completed before wake_up(): as=ffffffc0cc638200
To fix this problem we can just move the wake_up() under the ps->lock.
There should be no issues there that I'm aware of.
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To understand all the Linux-USB framework, you'll use these resources:
* This source code. This is necessarily an evolving work, and
includes kerneldoc that should help you get a current overview.
("make pdfdocs", and then look at "usb.pdf" for host side and
"gadget.pdf" for peripheral side.) Also, Documentation/usb has
more information.
* The USB 2.0 specification (from www.usb.org), with supplements
such as those for USB OTG and the various device classes.
The USB specification has a good overview chapter, and USB
peripherals conform to the widely known "Chapter 9".
* Chip specifications for USB controllers. Examples include
host controllers (on PCs, servers, and more); peripheral
controllers (in devices with Linux firmware, like printers or
cell phones); and hard-wired peripherals like Ethernet adapters.
* Specifications for other protocols implemented by USB peripheral
functions. Some are vendor-specific; others are vendor-neutral
but just standardized outside of the www.usb.org team.
Here is a list of what each subdirectory here is, and what is contained in
them.
core/ - This is for the core USB host code, including the
usbfs files and the hub class driver ("hub_wq").
host/ - This is for USB host controller drivers. This
includes UHCI, OHCI, EHCI, and others that might
be used with more specialized "embedded" systems.
gadget/ - This is for USB peripheral controller drivers and
the various gadget drivers which talk to them.
Individual USB driver directories. A new driver should be added to the
first subdirectory in the list below that it fits into.
image/ - This is for still image drivers, like scanners or
digital cameras.
../input/ - This is for any driver that uses the input subsystem,
like keyboard, mice, touchscreens, tablets, etc.
../media/ - This is for multimedia drivers, like video cameras,
radios, and any other drivers that talk to the v4l
subsystem.
../net/ - This is for network drivers.
serial/ - This is for USB to serial drivers.
storage/ - This is for USB mass-storage drivers.
class/ - This is for all USB device drivers that do not fit
into any of the above categories, and work for a range
of USB Class specified devices.
misc/ - This is for all USB device drivers that do not fit
into any of the above categories.