[PATCH 3.12 70/94] PM / sleep: Fix request_firmware() error at resume
From: Jiri Slaby
Date: Wed Jul 30 2014 - 08:24:54 EST
From: Takashi Iwai <tiwai@xxxxxxx>
3.12-stable review patch. If anyone has any objections, please let me know.
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:
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())
Signed-off-by: Takashi Iwai <tiwai@xxxxxxx>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
Signed-off-by: Jiri Slaby <jslaby@xxxxxxx>
kernel/power/process.c | 1 +
1 file changed, 1 insertion(+)
diff --git a/kernel/power/process.c b/kernel/power/process.c
index 06ec8869dbf1..14f9a8d4725d 100644
@@ -184,6 +184,7 @@ void thaw_processes(void)
printk("Restarting tasks ... ");
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