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authorSeth Forshee <seth.forshee@canonical.com>2011-07-26 09:56:07 -0500
committerGreg Kroah-Hartman <gregkh@suse.de>2011-11-11 09:36:43 -0800
commit6eb006c6079fd54a260caf7dfb3c750f65f4b1fc (patch)
treee7827f6fe9bbf0b2ffc7ea972840b1c82e2271cd /drivers/usb
parentb710365a9a762cb6cf931a066648daf9a941a9af (diff)
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usb_storage: Don't freeze in usb-stor-scan
commit f02fe890ece7d695a5744b20525d45312382e6e4 upstream. Scanning cannot be run during suspend or hibernation, but if usb-stor-scan freezes another thread waiting on scanning to complete may fail to freeze. However, if usb-stor-scan is left freezable without ever actually freezing then the freezer will wait on it to exit, and threads waiting for scanning to finish will no longer be blocked. One problem with this approach is that usb-stor-scan has a delay to wait for devices to settle (which is currently the only point where it can freeze). To work around this we can request that the freezer send a fake signal when freezing, then use interruptible sleep to wake the thread early when freezing happens. To make this happen, the following changes are made to usb-stor-scan: * Use set_freezable_with_signal() instead of set_freezable() to request a fake signal when freezing * Use wait_event_interruptible_timeout() instead of wait_event_freezable_timeout() to avoid freezing Signed-off-by: Seth Forshee <seth.forshee@canonical.com> Acked-by: Alan Stern <stern@rowland.harvard.edu> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Diffstat (limited to 'drivers/usb')
-rw-r--r--drivers/usb/storage/usb.c16
1 files changed, 13 insertions, 3 deletions
diff --git a/drivers/usb/storage/usb.c b/drivers/usb/storage/usb.c
index 0ca0958..c325e69 100644
--- a/drivers/usb/storage/usb.c
+++ b/drivers/usb/storage/usb.c
@@ -831,12 +831,22 @@ static int usb_stor_scan_thread(void * __us)
dev_dbg(dev, "device found\n");
- set_freezable();
- /* Wait for the timeout to expire or for a disconnect */
+ set_freezable_with_signal();
+ /*
+ * Wait for the timeout to expire or for a disconnect
+ *
+ * We can't freeze in this thread or we risk causing khubd to
+ * 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.
+ */
if (delay_use > 0) {
dev_dbg(dev, "waiting for device to settle "
"before scanning\n");
- wait_event_freezable_timeout(us->delay_wait,
+ wait_event_interruptible_timeout(us->delay_wait,
test_bit(US_FLIDX_DONT_SCAN, &us->dflags),
delay_use * HZ);
}