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    Subject[PATCH v3] USB:gadget: Fix a warning while loading g_mass_storage
    Date
    From: Yang Wei <Wei.Yang@windriver.com>

    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, because the spinlock isn't held
    at this point.

    Signed-off-by: Yang Wei <Wei.Yang@windriver.com>
    Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
    ---
    drivers/usb/gadget/f_mass_storage.c | 6 ++++--
    1 file changed, 4 insertions(+), 2 deletions(-)

    Hi Alan,

    Thanks for your review, there are a few changes in v3:

    1) Fix a coding style issue.
    2) Refine the commit log

    Regards
    Wei

    diff --git a/drivers/usb/gadget/f_mass_storage.c b/drivers/usb/gadget/f_mass_storage.c
    index b963939..0cd8f21 100644
    --- a/drivers/usb/gadget/f_mass_storage.c
    +++ b/drivers/usb/gadget/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;

    /*
    @@ -2421,6 +2422,7 @@ static void handle_exception(struct fsg_common *common)
    }
    common->state = FSG_STATE_IDLE;
    }
    + new_fsg = common->new_fsg;
    spin_unlock_irq(&common->lock);

    /* Carry out any extra actions required for the exception */
    @@ -2460,8 +2462,8 @@ static void handle_exception(struct fsg_common *common)
    break;

    case FSG_STATE_CONFIG_CHANGE:
    - do_set_interface(common, common->new_fsg);
    - if (common->new_fsg)
    + do_set_interface(common, new_fsg);
    + if (new_fsg)
    usb_composite_setup_continue(common->cdev);
    break;

    --
    1.7.9.5


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