On Tuesday, July 15, 2014 08:51:27 AM Takashi Iwai wrote:
> 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.
>
> Bugzilla: https://bugzilla.novell.com/show_bug.cgi?id=873790
> Cc: <[email protected]>
> Signed-off-by: Takashi Iwai <[email protected]>
Applied, thanks for fixing this up!
> ---
> kernel/power/process.c | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/kernel/power/process.c b/kernel/power/process.c
> index 0ca8d83e2369..4ee194eb524b 100644
> --- a/kernel/power/process.c
> +++ b/kernel/power/process.c
> @@ -186,6 +186,7 @@ void thaw_processes(void)
>
> printk("Restarting tasks ... ");
>
> + __usermodehelper_set_disable_depth(UMH_FREEZING);
> thaw_workqueues();
>
> read_lock(&tasklist_lock);
>
--
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
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