Commit 4320f6b1 authored by Takashi Iwai's avatar Takashi Iwai Committed by Rafael J. Wysocki

PM / sleep: Fix request_firmware() error at resume

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: 247bc037 (PM / Sleep: Mitigate race between the freezer and request_firmware())
Link: https://bugzilla.novell.com/show_bug.cgi?id=873790
Cc: 3.4+ <stable@vger.kernel.org> # 3.4+
Signed-off-by: default avatarTakashi Iwai <tiwai@suse.de>
Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
parent 1795cd9b
...@@ -186,6 +186,7 @@ void thaw_processes(void) ...@@ -186,6 +186,7 @@ void thaw_processes(void)
printk("Restarting tasks ... "); printk("Restarting tasks ... ");
__usermodehelper_set_disable_depth(UMH_FREEZING);
thaw_workqueues(); thaw_workqueues();
read_lock(&tasklist_lock); read_lock(&tasklist_lock);
......
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