[PATCH] PM / sleep: Fix request_firmware() error at resume

From: Takashi Iwai
Date: Tue Jul 15 2014 - 02:51:35 EST

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:

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: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Takashi Iwai <tiwai@xxxxxxx>
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);


To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/