[PATCH] usb hub: send clear_tt_buffer_complete events when canceling TT clear work
From: Octavian Purdila
Date: Mon Oct 01 2012 - 12:55:15 EST
There is a race condition in the USB hub code with regard to handling
TT clear requests that can get the HCD driver in a deadlock. Usually
when an TT clear request is scheduled it will be executed immediately:
<7>[ 6.077583] usb 2-1.3: unlink qh1-0e01/f4d4db00 start 0 [1/2 us]
<3>[ 6.078041] usb 2-1: clear tt buffer port 3, a3 ep2 t04048d82
<7>[ 6.078299] hub_tt_work:731
<7>[ 9.309089] usb 2-1.5: link qh1-0e01/f4d506c0 start 0 [1/2 us]
<7>[ 9.324526] ehci_hcd 0000:00:1d.0: reused qh f4d4db00 schedule
<7>[ 9.324539] usb 2-1.3: link qh1-0e01/f4d4db00 start 0 [1/2 us]
<7>[ 9.341530] usb 1-1.1: link qh4-0e01/f397aec0 start 2 [1/2 us]
<7>[ 10.116159] usb 2-1.3: unlink qh1-0e01/f4d4db00 start 0 [1/2 us]
<3>[ 10.116459] usb 2-1: clear tt buffer port 3, a3 ep2 t04048d82
<7>[ 10.116537] hub_tt_work:731
However, if a suspend operation is triggered before hub_tt_work is
scheduled, hub_quiesce will cancel the work without notifying the HCD
driver:
<3>[ 35.033941] usb 2-1: clear tt buffer port 3, a3 ep2 t04048d80
<5>[ 35.034022] sd 0:0:0:0: [sda] Stopping disk
<7>[ 35.034039] hub 2-1:1.0: hub_suspend
<7>[ 35.034067] usb 2-1: unlink qh256-0001/f3b1ab00 start 1 [1/0 us]
<7>[ 35.035085] hub 1-0:1.0: hub_suspend
<7>[ 35.035102] usb usb1: bus suspend, wakeup 0
<7>[ 35.035106] ehci_hcd 0000:00:1a.0: suspend root hub
<7>[ 35.035298] hub 2-0:1.0: hub_suspend
<7>[ 35.035313] usb usb2: bus suspend, wakeup 0
<7>[ 35.035315] ehci_hcd 0000:00:1d.0: suspend root hub
<6>[ 35.250017] PM: suspend of devices complete after 216.979 msecs
<6>[ 35.250822] PM: late suspend of devices complete after 0.799 msecs
<7>[ 35.252343] ehci_hcd 0000:00:1d.0: wakeup: 1
<7>[ 35.262923] ehci_hcd 0000:00:1d.0: --> PCI D3hot
<7>[ 35.263302] ehci_hcd 0000:00:1a.0: wakeup: 1
<7>[ 35.273912] ehci_hcd 0000:00:1a.0: --> PCI D3hot
<6>[ 35.274254] PM: noirq suspend of devices complete after 23.442 msecs
<6>[ 35.274975] ACPI: Preparing to enter system sleep state S3
<6>[ 35.292666] PM: Saving platform NVS memory
<7>[ 35.295030] Disabling non-boot CPUs ...
<6>[ 35.297351] CPU 1 is now offline
<6>[ 35.300345] CPU 2 is now offline
<6>[ 35.303929] CPU 3 is now offline
<7>[ 35.303931] lockdep: fixing up alternatives.
<6>[ 35.304825] Extended CMOS year: 2000
When the device will resume the EHCI driver will get stuck in
ehci_endpoint_disable waiting for the tt_clearing flag to reset:
<0>[ 47.610967] usb 2-1.3: **** DPM device timeout ****
<7>[ 47.610972] f2f11c60 00000092 f2f11c0c c10624a5 00000003 f4c6e880 c1c8a4c0 c1c8a4c0
<7>[ 47.610983] 15c55698 0000000b f56b34c0 f2a45b70 f4c6e880 00000082 f2a4602c f2f11c30
<7>[ 47.610993] c10787f8 f4cac000 f2a45b70 00000000 f4cac010 f2f11c58 00000046 00000001
<7>[ 47.611004] Call Trace:
<7>[ 47.611006] [<c10624a5>] ? sched_clock_cpu+0xf5/0x160
<7>[ 47.611019] [<c10787f8>] ? lock_release_holdtime.part.22+0x88/0xf0
<7>[ 47.611026] [<c103ed46>] ? lock_timer_base.isra.35+0x26/0x50
<7>[ 47.611034] [<c17592d3>] ? schedule_timeout+0x133/0x290
<7>[ 47.611044] [<c175b43e>] schedule+0x1e/0x50
<7>[ 47.611051] [<c17592d8>] schedule_timeout+0x138/0x290
<7>[ 47.611057] [<c10624a5>] ? sched_clock_cpu+0xf5/0x160
<7>[ 47.611063] [<c103e560>] ? usleep_range+0x40/0x40
<7>[ 47.611070] [<c1759445>] schedule_timeout_uninterruptible+0x15/0x20
<7>[ 47.611077] [<c14935f4>] ehci_endpoint_disable+0x64/0x160
<7>[ 47.611084] [<c147d1ee>] ? usb_hcd_flush_endpoint+0x10e/0x1d0
<7>[ 47.611092] [<c1165663>] ? sysfs_add_file+0x13/0x20
<7>[ 47.611100] [<c147d5a9>] usb_hcd_disable_endpoint+0x29/0x40
<7>[ 47.611107] [<c147fafc>] usb_disable_endpoint+0x5c/0x80
<7>[ 47.611111] [<c147fb57>] usb_disable_interface+0x37/0x50
<7>[ 47.611116] [<c1477650>] usb_reset_and_verify_device+0x4b0/0x640
<7>[ 47.611122] [<c1474665>] ? hub_port_status+0xb5/0x100
<7>[ 47.611129] [<c147a975>] usb_port_resume+0xd5/0x220
<7>[ 47.611136] [<c148877f>] generic_resume+0xf/0x30
<7>[ 47.611142] [<c14821a3>] usb_resume+0x133/0x180
<7>[ 47.611147] [<c1473b10>] ? usb_dev_thaw+0x10/0x10
<7>[ 47.611152] [<c1473b1d>] usb_dev_resume+0xd/0x10
<7>[ 47.611157] [<c13baa60>] dpm_run_callback+0x40/0xb0
<7>[ 47.611164] [<c13bdb03>] ? pm_runtime_enable+0x43/0x70
<7>[ 47.611171] [<c13bafc6>] device_resume+0x1a6/0x2c0
<7>[ 47.611177] [<c13ba940>] ? dpm_show_time+0xe0/0xe0
<7>[ 47.611183] [<c13bb0f9>] async_resume+0x19/0x40
<7>[ 47.611189] [<c10580c4>] async_run_entry_fn+0x64/0x160
<7>[ 47.611196] [<c104a244>] ? process_one_work+0x104/0x480
<7>[ 47.611203] [<c104a24c>] ? process_one_work+0x10c/0x480
<7>[ 47.611209] [<c104a2c0>] process_one_work+0x180/0x480
<7>[ 47.611215] [<c104a244>] ? process_one_work+0x104/0x480
<7>[ 47.611220] [<c1058060>] ? async_schedule+0x10/0x10
<7>[ 47.611226] [<c104c15c>] worker_thread+0x11c/0x2f0
<7>[ 47.611233] [<c104c040>] ? manage_workers.isra.27+0x1f0/0x1f0
<7>[ 47.611239] [<c10507f8>] kthread+0x78/0x80
<7>[ 47.611244] [<c1750000>] ? timer_cpu_notify+0xd6/0x20d
<7>[ 47.611253] [<c1050780>] ? __init_kthread_worker+0x60/0x60
<7>[ 47.611258] [<c176357e>] kernel_thread_helper+0x6/0xd
<7>[ 47.611283] ------------[ cut here ]------------
This patch notifies the HCD driver via clear_tt_buffer_complete
when canceling TT clear work so that the EHCI driver has a chance to
clear its tt_clearing flag.
Signed-off-by: Octavian Purdila <octavian.purdila@xxxxxxxxx>
---
drivers/usb/core/hub.c | 64 ++++++++++++++++++++++++++++++-----------------
1 files changed, 41 insertions(+), 23 deletions(-)
diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
index 128a804..83b07c2 100644
--- a/drivers/usb/core/hub.c
+++ b/drivers/usb/core/hub.c
@@ -711,43 +711,38 @@ resubmit:
static inline int
hub_clear_tt_buffer (struct usb_device *hdev, u16 devinfo, u16 tt)
{
- return usb_control_msg(hdev, usb_sndctrlpipe(hdev, 0),
+ int status = usb_control_msg(hdev, usb_sndctrlpipe(hdev, 0),
HUB_CLEAR_TT_BUFFER, USB_RT_PORT, devinfo,
tt, NULL, 0, 1000);
+ if (status)
+ dev_err(&hdev->dev, "clear tt %d (%04x) error %d\n",
+ tt, devinfo, status);
+
+ return status;
}
-/*
- * enumeration blocks khubd for a long time. we use keventd instead, since
- * long blocking there is the exception, not the rule. accordingly, HCDs
- * talking to TTs must queue control transfers (not just bulk and iso), so
- * both can talk to the same hub concurrently.
- */
-static void hub_tt_work(struct work_struct *work)
+static void hub_tt_run_list(struct usb_hub *hub, int limit, bool do_clear)
{
- struct usb_hub *hub =
- container_of(work, struct usb_hub, tt.clear_work);
- unsigned long flags;
- int limit = 100;
+ unsigned long flags, work = 0;
- spin_lock_irqsave (&hub->tt.lock, flags);
- while (--limit && !list_empty (&hub->tt.clear_list)) {
+ spin_lock_irqsave(&hub->tt.lock, flags);
+ while (!list_empty(&hub->tt.clear_list)) {
struct list_head *next;
struct usb_tt_clear *clear;
struct usb_device *hdev = hub->hdev;
const struct hc_driver *drv;
- int status;
+
+ if (limit && ++work > limit)
+ break;
next = hub->tt.clear_list.next;
clear = list_entry (next, struct usb_tt_clear, clear_list);
- list_del (&clear->clear_list);
+ list_del(&clear->clear_list);
/* drop lock so HCD can concurrently report other TT errors */
spin_unlock_irqrestore (&hub->tt.lock, flags);
- status = hub_clear_tt_buffer (hdev, clear->devinfo, clear->tt);
- if (status)
- dev_err (&hdev->dev,
- "clear tt %d (%04x) error %d\n",
- clear->tt, clear->devinfo, status);
+ if (do_clear)
+ hub_clear_tt_buffer(hdev, clear->devinfo, clear->tt);
/* Tell the HCD, even if the operation failed */
drv = clear->hcd->driver;
@@ -757,7 +752,30 @@ static void hub_tt_work(struct work_struct *work)
kfree(clear);
spin_lock_irqsave(&hub->tt.lock, flags);
}
- spin_unlock_irqrestore (&hub->tt.lock, flags);
+ spin_unlock_irqrestore(&hub->tt.lock, flags);
+}
+
+/*
+ * enumeration blocks khubd for a long time. we use keventd instead, since
+ * long blocking there is the exception, not the rule. accordingly, HCDs
+ * talking to TTs must queue control transfers (not just bulk and iso), so
+ * both can talk to the same hub concurrently.
+ */
+static void hub_tt_work(struct work_struct *work)
+{
+ struct usb_hub *hub =
+ container_of(work, struct usb_hub, tt.clear_work);
+
+ hub_tt_run_list(hub, 100, 1);
+}
+
+static void hub_cancel_tt_work(struct usb_hub *hub)
+{
+ cancel_work_sync(&hub->tt.clear_work);
+ /* Tell HCD drivers that TT work is complete even when
+ * canceling work otherwise they will wait forever for a
+ * clear_tt_buffer_complete event. */
+ hub_tt_run_list(hub, 0, 0);
}
/**
@@ -1201,7 +1219,7 @@ static void hub_quiesce(struct usb_hub *hub, enum hub_quiescing_type type)
if (hub->has_indicators)
cancel_delayed_work_sync(&hub->leds);
if (hub->tt.hub)
- cancel_work_sync(&hub->tt.clear_work);
+ hub_cancel_tt_work(hub);
}
/* caller has locked the hub device */
--
1.7.5.4
--
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