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    Subject[PATCH 3.14 80/87] PM / sleep: Fix request_firmware() error at resume
    Date
    3.14-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Takashi Iwai <tiwai@suse.de>

    commit 4320f6b1d9db4ca912c5eb6ecb328b2e090e1586 upstream.

    The commit [247bc037: PM / Sleep: Mitigate race between the freezer
    and request_firmware()] introduced the finer state control, but it
    also leads to a new bug; for example, a bug report regarding the
    firmware loading of intel BT device at suspend/resume:
    https://bugzilla.novell.com/show_bug.cgi?id=873790

    The root cause seems to be a small window between the process resume
    and the clear of usermodehelper lock. The request_firmware() function
    checks the UMH lock and gives up when it's in UMH_DISABLE state. This
    is for avoiding the invalid f/w loading during suspend/resume phase.
    The problem is, however, that usermodehelper_enable() is called at the
    end of thaw_processes(). Thus, a thawed process in between can kick
    off the f/w loader code path (in this case, via btusb_setup_intel())
    even before the call of usermodehelper_enable(). Then
    usermodehelper_read_trylock() returns an error and request_firmware()
    spews WARN_ON() in the end.

    This oneliner patch fixes the issue just by setting to UMH_FREEZING
    state again before restarting tasks, so that the call of
    request_firmware() will be blocked until the end of this function
    instead of returning an error.

    Fixes: 247bc0374254 (PM / Sleep: Mitigate race between the freezer and request_firmware())
    Link: https://bugzilla.novell.com/show_bug.cgi?id=873790
    Signed-off-by: Takashi Iwai <tiwai@suse.de>
    Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    kernel/power/process.c | 1 +
    1 file changed, 1 insertion(+)

    --- a/kernel/power/process.c
    +++ b/kernel/power/process.c
    @@ -184,6 +184,7 @@ void thaw_processes(void)

    printk("Restarting tasks ... ");

    + __usermodehelper_set_disable_depth(UMH_FREEZING);
    thaw_workqueues();

    read_lock(&tasklist_lock);



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