[PATCH 5/5] USB:gadget: Fix a warning while loading g_mass_storage

From: Michal Nazarewicz
Date: Wed Aug 27 2014 - 17:04:41 EST

From: Yang Wei <Wei.Yang@xxxxxxxxxxxxx>

While loading g_mass_storage module, the following warning
is triggered.

WARNING: at drivers/usb/gadget/composite.c:
usb_composite_setup_continue: Unexpected call
Modules linked in: fat vfat minix nls_cp437 nls_iso8859_1 g_mass_storage
[<800179cc>] (unwind_backtrace+0x0/0x104) from [<80619608>] (dump_stack+0x20/0x24)
[<80619608>] (dump_stack+0x20/0x24) from [<80025100>] (warn_slowpath_common+0x64/0x74)
[<80025100>] (warn_slowpath_common+0x64/0x74) from [<800251cc>] (warn_slowpath_fmt+0x40/0x48)
[<800251cc>] (warn_slowpath_fmt+0x40/0x48) from [<7f047774>] (usb_composite_setup_continue+0xb4/0xbc [g_mass_storage])
[<7f047774>] (usb_composite_setup_continue+0xb4/0xbc [g_mass_storage]) from [<7f047ad4>] (handle_exception+0x358/0x3e4 [g_mass_storage])
[<7f047ad4>] (handle_exception+0x358/0x3e4 [g_mass_storage]) from [<7f048080>] (fsg_main_thread+0x520/0x157c [g_mass_storage])
[<7f048080>] (fsg_main_thread+0x520/0x157c [g_mass_storage]) from [<8004bc90>] (kthread+0x98/0x9c)
[<8004bc90>] (kthread+0x98/0x9c) from [<8000faec>] (kernel_thread_exit+0x0/0x8)

The root cause is that the existing code fails to take into
account the possibility that common->new_fsg can change while
do_set_interface() is running, so the value of common->new_fsg
that gets tested after do_set_interface returns needs to be
the same as the value used by do_set_interface.

Signed-off-by: Yang Wei <Wei.Yang@xxxxxxxxxxxxx>
Signed-off-by: Michal Nazarewicz <mina86@xxxxxxxxxx>
Acked-by: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>
drivers/usb/gadget/function/f_mass_storage.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/usb/gadget/function/f_mass_storage.c b/drivers/usb/gadget/function/f_mass_storage.c
index 811929c..cf4b202 100644
--- a/drivers/usb/gadget/function/f_mass_storage.c
+++ b/drivers/usb/gadget/function/f_mass_storage.c
@@ -2342,6 +2342,7 @@ static void handle_exception(struct fsg_common *common)
struct fsg_buffhd *bh;
enum fsg_state old_state;
struct fsg_lun *curlun;
+ struct fsg_dev *new_fsg;
unsigned int exception_req_tag;

@@ -2460,8 +2461,9 @@ static void handle_exception(struct fsg_common *common)

- do_set_interface(common, common->new_fsg);
- if (common->new_fsg)
+ new_fsg = common->new_fsg;
+ do_set_interface(common, new_fsg);
+ if (new_fsg)


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