usb_storage: don't use set_freezable_with_signal()

The current implementation of set_freezable_with_signal() is buggy and
tricky to get right.  usb-storage is the only user and its use can be
avoided trivially.

All usb-storage wants is to be able to sleep with timeout and get
woken up if freezing() becomes true.  This can be trivially
implemented by doing interruptible wait w/ freezing() included in the
wait condition.  There's no reason to use set_freezable_with_signal().

Perform interruptible wait on freezing() instead of using
set_freezable_with_signal(), which is scheduled for removal.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: "Rafael J. Wysocki" <rjw@sisk.pl>
Cc: Seth Forshee <seth.forshee@canonical.com>
Cc: Alan Stern <stern@rowland.harvard.edu>
Cc: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/drivers/usb/storage/usb.c b/drivers/usb/storage/usb.c
index c325e69..aa84b3d 100644 (file)
--- a/drivers/usb/storage/usb.c
+++ b/drivers/usb/storage/usb.c
@@ -831,7 +831,8 @@ static int usb_stor_scan_thread(void * __us)
 
        dev_dbg(dev, "device found\n");
 
-       set_freezable_with_signal();
+       set_freezable();
+
        /*
         * Wait for the timeout to expire or for a disconnect
         *
@@ -839,16 +840,16 @@ static int usb_stor_scan_thread(void * __us)
         * fail to freeze, but we can't be non-freezable either. Nor can
         * khubd freeze while waiting for scanning to complete as it may
         * hold the device lock, causing a hang when suspending devices.
-        * So we request a fake signal when freezing and use
-        * interruptible sleep to kick us out of our wait early when
-        * freezing happens.
+        * So instead of using wait_event_freezable(), explicitly test
+        * for (DONT_SCAN || freezing) in interruptible wait and proceed
+        * if any of DONT_SCAN, freezing or timeout has happened.
         */
        if (delay_use > 0) {
                dev_dbg(dev, "waiting for device to settle "
                                "before scanning\n");
                wait_event_interruptible_timeout(us->delay_wait,
-                               test_bit(US_FLIDX_DONT_SCAN, &us->dflags),
-                               delay_use * HZ);
+                               test_bit(US_FLIDX_DONT_SCAN, &us->dflags) ||
+                               freezing(current), delay_use * HZ);
        }
 
        /* If the device is still connected, perform the scanning */