As a holdover from the old g_file_storage gadget, the g_mass_storage
legacy gadget driver attempts to unregister itself when its main
operating thread terminates (if it hasn't been unregistered already).
This is not strictly necessary; it was never more than an attempt to
have the gadget fail cleanly if something went wrong and the main
thread was killed.
However, now that the UDC core manages gadget drivers independently of
UDC drivers, this scheme doesn't work any more. A simple test:
modprobe dummy-hcd
modprobe g-mass-storage file=...
rmmod dummy-hcd
ends up in a deadlock with the following backtrace:
sysrq: SysRq : Show Blocked State
task PC stack pid father
file-storage D 0 1130 2 0x00000000
Call Trace:
__schedule+0x53e/0x58c
schedule+0x6e/0x77
schedule_preempt_disabled+0xd/0xf
__mutex_lock.isra.1+0x129/0x224
? _raw_spin_unlock_irqrestore+0x12/0x14
__mutex_lock_slowpath+0x12/0x14
mutex_lock+0x28/0x2b
usb_gadget_unregister_driver+0x29/0x9b [udc_core]
usb_composite_unregister+0x10/0x12 [libcomposite]
msg_cleanup+0x1d/0x20 [g_mass_storage]
msg_thread_exits+0xd/0xdd7 [g_mass_storage]
fsg_main_thread+0x1395/0x13d6 [usb_f_mass_storage]
? __schedule+0x573/0x58c
kthread+0xd9/0xdb
? do_set_interface+0x25c/0x25c [usb_f_mass_storage]
? init_completion+0x1e/0x1e
ret_from_fork+0x19/0x24
rmmod D 0 1155 683 0x00000000
Call Trace:
__schedule+0x53e/0x58c
schedule+0x6e/0x77
schedule_timeout+0x26/0xbc
? __schedule+0x573/0x58c
do_wait_for_common+0xb3/0x128
? usleep_range+0x81/0x81
? wake_up_q+0x3f/0x3f
wait_for_common+0x2e/0x45
wait_for_completion+0x17/0x19
fsg_common_put+0x34/0x81 [usb_f_mass_storage]
fsg_free_inst+0x13/0x1e [usb_f_mass_storage]
usb_put_function_instance+0x1a/0x25 [libcomposite]
msg_unbind+0x2a/0x42 [g_mass_storage]
__composite_unbind+0x4a/0x6f [libcomposite]
composite_unbind+0x12/0x14 [libcomposite]
usb_gadget_remove_driver+0x4f/0x77 [udc_core]
usb_del_gadget_udc+0x52/0xcc [udc_core]
dummy_udc_remove+0x27/0x2c [dummy_hcd]
platform_drv_remove+0x1d/0x31
device_release_driver_internal+0xe9/0x16d
device_release_driver+0x11/0x13
bus_remove_device+0xd2/0xe2
device_del+0x19f/0x221
? selinux_capable+0x22/0x27
platform_device_del+0x21/0x63
platform_device_unregister+0x10/0x1a
cleanup+0x20/0x817 [dummy_hcd]
SyS_delete_module+0x10c/0x197
? ____fput+0xd/0xf
? task_work_run+0x55/0x62
? prepare_exit_to_usermode+0x65/0x75
do_fast_syscall_32+0x86/0xc3
entry_SYSENTER_32+0x4e/0x7c
What happens is that removing the dummy-hcd driver causes the UDC core
to unbind the gadget driver, which it does while holding the udc_lock
mutex. The unbind routine in g_mass_storage tells the main thread to
exit and waits for it to terminate.
But as mentioned above, when the main thread exits it tries to
unregister the mass-storage function driver. Via the composite
framework this ends up calling usb_gadget_unregister_driver(), which
tries to acquire the udc_lock mutex. The result is deadlock.
The simplest way to fix the problem is not to be so clever: The main
thread doesn't have to unregister the function driver. The side
effects won't be so terrible; if the gadget is still attached to a USB
host when the main thread is killed, it will appear to the host as
though the gadget's firmware has crashed -- a reasonably accurate
interpretation, and an all-too-common occurrence for USB mass-storage
devices.
In fact, the code to unregister the driver when the main thread exits
is specific to g-mass-storage; it is not used when f-mass-storage is
included as a function in a larger composite device. Therefore the
entire mechanism responsible for this (the fsg_operations structure
with its ->thread_exits method, the fsg_common_set_ops() routine, and
the msg_thread_exits() callback routine) can all be eliminated. Even
the msg_registered bitflag can be removed, because now the driver is
unregistered in only one place rather than in two places.
Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
CC: <stable@vger.kernel.org>
Acked-by: Felipe Balbi <felipe.balbi@linux.intel.com>
Acked-by: Michal Nazarewicz <mina86@mina86.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Introduce an attribute "inquiry_string" to the lun.
In some environments, e. g. BIOS boot menus, the inquiry string
is the only information about devices presented to the user. The
default string depends on the "cdrom" bit of the first lun as
well as the kernel version and allows no further customization.
So without access to the client it is not obvious which gadget is
active at a given point and what any of the available luns might
contain.
If "inquiry_string" is ignored or set to the empty string, the
old behavior is preserved.
Signed-off-by: Philipp Gesang <philipp.gesang@intra2net.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>
When binding the function to usb_configuration, check whether the thread
is running before starting another one. Without that, when function
instance is added to multiple configurations, fsg_bing starts multiple
threads with all but the latest one being forgotten by the driver. This
leads to obvious thread leaks, possible lockups when trying to halt the
machine and possible more issues.
This fixes issues with legacy/multi¹ gadget as well as configfs gadgets
when mass_storage function is added to multiple configurations.
This change also simplifies API since the legacy gadgets no longer need
to worry about starting the thread by themselves (which was where bug
in legacy/multi was in the first place).
N.B., this patch doesn’t address adding single mass_storage function
instance to a single configuration twice. Thankfully, there’s no
legitimate reason for such setup plus, if I’m not mistaken, configfs
gadget doesn’t even allow it to be expressed.
¹ I have no example failure though. Conclusion that legacy/multi has
a bug is based purely on me reading the code.
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Michal Nazarewicz <mina86@mina86.com>
Tested-by: Ivaylo Dimitrov <ivo.g.dimitrov.75@gmail.com>
Cc: Alan Stern <stern@rowland.harvard.edu>
Cc: <stable@vger.kernel.org>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>
This patch replace dynamicly allocated luns array with static one.
This simplifies the code of mass storage function and modules.
Signed-off-by: Krzysztof Opasiak <k.opasiak@samsung.com>
Acked-by: Michal Nazarewicz <mina86@mina86.com>
The drivers/usb/gadget directory contains many files.
Files which are related can be distributed into separate directories.
This patch moves the USB functions implementations into a separate directory.
Signed-off-by: Andrzej Pietrasiewicz <andrzej.p@samsung.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>
