This is a note to let you know that I've just added the patch titled
usb: host: xhci: add mutex for non-thread-safe data
to my usb git tree which can be found at
git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb.git
in the usb-linus branch.
The patch will show up in the next release of the linux-next tree
(usually sometime within the next 24 hours during the week.)
The patch will hopefully also be merged in Linus's tree for the
next -rc kernel release.
If you have any questions about this process, please let me know.
>From a00918d0521df1c7a2ec9143142a3ea998c8526d Mon Sep 17 00:00:00 2001
From: Chris Bainbridge <chris.bainbridge@xxxxxxxxx>
Date: Tue, 19 May 2015 16:30:51 +0300
Subject: usb: host: xhci: add mutex for non-thread-safe data
Regression in commit 638139eb95d2 ("usb: hub: allow to process more usb
hub events in parallel")
The regression resulted in intermittent failure to initialise a 10-port
hub (with three internal VL812 4-port hub controllers) on boot, with a
failure rate of around 8%, due to multiple race conditions when
accessing addr_dev and slot_id in struct xhci_hcd.
This regression also exposed a problem with xhci_setup_device, which
"should be protected by the usb_address0_mutex" but no longer is due to
commit 6fecd4f2a58c ("USB: separate usb_address0 mutexes for each bus")
With separate buses (and locks) it is no longer the case that a single
lock will protect xhci_setup_device from accesses by two parallel
threads processing events on the two buses.
Fix this by adding a mutex to protect addr_dev and slot_id in struct
xhci_hcd, and by making the assignment of slot_id atomic.
Fixes multiple boot errors:
[ 0.583008] xhci_hcd 0000:00:14.0: Bad Slot ID 2
[ 0.583009] xhci_hcd 0000:00:14.0: Could not allocate xHCI USB device data structures
[ 0.583012] usb usb1-port3: couldn't allocate usb_device
And:
[ 0.637409] xhci_hcd 0000:00:14.0: Error while assigning device slot ID
[ 0.637417] xhci_hcd 0000:00:14.0: Max number of devices this xHCI host supports is 32.
[ 0.637421] usb usb1-port1: couldn't allocate usb_device
And:
[ 0.753372] xhci_hcd 0000:00:14.0: ERROR: unexpected setup context command completion code 0x0.
[ 0.753373] usb 1-3: hub failed to enable device, error -22
[ 0.753400] xhci_hcd 0000:00:14.0: Error while assigning device slot ID
[ 0.753402] xhci_hcd 0000:00:14.0: Max number of devices this xHCI host supports is 32.
[ 0.753403] usb usb1-port3: couldn't allocate usb_device
And:
[ 11.018386] usb 1-3: device descriptor read/all, error -110
And:
[ 5.753838] xhci_hcd 0000:00:14.0: Timeout while waiting for setup device command
Tested with 200 reboots, resulting in no USB hub init related errors.
Fixes: 638139eb95d2 ("usb: hub: allow to process more usb hub events in parallel")
Link: https://lkml.kernel.org/g/CAP-bSRb=A0iEYobdGCLpwynS7pkxpt_9ZnwyZTPVAoy0Y=Zo3Q@xxxxxxxxxxxxxx
Signed-off-by: Chris Bainbridge <chris.bainbridge@xxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx> # 3.18+
[changed git commit description style for checkpatch -Mathias]
Signed-off-by: Mathias Nyman <mathias.nyman@xxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/usb/host/xhci.c | 49 ++++++++++++++++++++++++++++++-------------------
drivers/usb/host/xhci.h | 2 ++
2 files changed, 32 insertions(+), 19 deletions(-)
diff --git a/drivers/usb/host/xhci.c b/drivers/usb/host/xhci.c
index 4299cbf47793..36bf089b708f 100644
--- a/drivers/usb/host/xhci.c
+++ b/drivers/usb/host/xhci.c
@@ -3682,18 +3682,21 @@ int xhci_alloc_dev(struct usb_hcd *hcd, struct usb_device *udev)
{
struct xhci_hcd *xhci = hcd_to_xhci(hcd);
unsigned long flags;
- int ret;
+ int ret, slot_id;
struct xhci_command *command;
command = xhci_alloc_command(xhci, false, false, GFP_KERNEL);
if (!command)
return 0;
+ /* xhci->slot_id and xhci->addr_dev are not thread-safe */
+ mutex_lock(&xhci->mutex);
spin_lock_irqsave(&xhci->lock, flags);
command->completion = &xhci->addr_dev;
ret = xhci_queue_slot_control(xhci, command, TRB_ENABLE_SLOT, 0);
if (ret) {
spin_unlock_irqrestore(&xhci->lock, flags);
+ mutex_unlock(&xhci->mutex);
xhci_dbg(xhci, "FIXME: allocate a command ring segment\n");
kfree(command);
return 0;
@@ -3702,8 +3705,10 @@ int xhci_alloc_dev(struct usb_hcd *hcd, struct usb_device *udev)
spin_unlock_irqrestore(&xhci->lock, flags);
wait_for_completion(command->completion);
+ slot_id = xhci->slot_id;
+ mutex_unlock(&xhci->mutex);
- if (!xhci->slot_id || command->status != COMP_SUCCESS) {
+ if (!slot_id || command->status != COMP_SUCCESS) {
xhci_err(xhci, "Error while assigning device slot ID\n");
xhci_err(xhci, "Max number of devices this xHCI host supports is %u.\n",
HCS_MAX_SLOTS(
@@ -3728,11 +3733,11 @@ int xhci_alloc_dev(struct usb_hcd *hcd, struct usb_device *udev)
* xhci_discover_or_reset_device(), which may be called as part of
* mass storage driver error handling.
*/
- if (!xhci_alloc_virt_device(xhci, xhci->slot_id, udev, GFP_NOIO)) {
+ if (!xhci_alloc_virt_device(xhci, slot_id, udev, GFP_NOIO)) {
xhci_warn(xhci, "Could not allocate xHCI USB device data structures\n");
goto disable_slot;
}
- udev->slot_id = xhci->slot_id;
+ udev->slot_id = slot_id;
#ifndef CONFIG_USB_DEFAULT_PERSIST
/*
@@ -3778,12 +3783,15 @@ static int xhci_setup_device(struct usb_hcd *hcd, struct usb_device *udev,
struct xhci_slot_ctx *slot_ctx;
struct xhci_input_control_ctx *ctrl_ctx;
u64 temp_64;
- struct xhci_command *command;
+ struct xhci_command *command = NULL;
+
+ mutex_lock(&xhci->mutex);
if (!udev->slot_id) {
xhci_dbg_trace(xhci, trace_xhci_dbg_address,
"Bad Slot ID %d", udev->slot_id);
- return -EINVAL;
+ ret = -EINVAL;
+ goto out;
}
virt_dev = xhci->devs[udev->slot_id];
@@ -3796,7 +3804,8 @@ static int xhci_setup_device(struct usb_hcd *hcd, struct usb_device *udev,
*/
xhci_warn(xhci, "Virt dev invalid for slot_id 0x%x!\n",
udev->slot_id);
- return -EINVAL;
+ ret = -EINVAL;
+ goto out;
}
if (setup == SETUP_CONTEXT_ONLY) {
@@ -3804,13 +3813,15 @@ static int xhci_setup_device(struct usb_hcd *hcd, struct usb_device *udev,
if (GET_SLOT_STATE(le32_to_cpu(slot_ctx->dev_state)) ==
SLOT_STATE_DEFAULT) {
xhci_dbg(xhci, "Slot already in default state\n");
- return 0;
+ goto out;
}
}
command = xhci_alloc_command(xhci, false, false, GFP_KERNEL);
- if (!command)
- return -ENOMEM;
+ if (!command) {
+ ret = -ENOMEM;
+ goto out;
+ }
command->in_ctx = virt_dev->in_ctx;
command->completion = &xhci->addr_dev;
@@ -3820,8 +3831,8 @@ static int xhci_setup_device(struct usb_hcd *hcd, struct usb_device *udev,
if (!ctrl_ctx) {
xhci_warn(xhci, "%s: Could not get input context, bad type.\n",
__func__);
- kfree(command);
- return -EINVAL;
+ ret = -EINVAL;
+ goto out;
}
/*
* If this is the first Set Address since device plug-in or
@@ -3848,8 +3859,7 @@ static int xhci_setup_device(struct usb_hcd *hcd, struct usb_device *udev,
spin_unlock_irqrestore(&xhci->lock, flags);
xhci_dbg_trace(xhci, trace_xhci_dbg_address,
"FIXME: allocate a command ring segment");
- kfree(command);
- return ret;
+ goto out;
}
xhci_ring_cmd_db(xhci);
spin_unlock_irqrestore(&xhci->lock, flags);
@@ -3896,10 +3906,8 @@ static int xhci_setup_device(struct usb_hcd *hcd, struct usb_device *udev,
ret = -EINVAL;
break;
}
- if (ret) {
- kfree(command);
- return ret;
- }
+ if (ret)
+ goto out;
temp_64 = xhci_read_64(xhci, &xhci->op_regs->dcbaa_ptr);
xhci_dbg_trace(xhci, trace_xhci_dbg_address,
"Op regs DCBAA ptr = %#016llx", temp_64);
@@ -3932,8 +3940,10 @@ static int xhci_setup_device(struct usb_hcd *hcd, struct usb_device *udev,
xhci_dbg_trace(xhci, trace_xhci_dbg_address,
"Internal device address = %d",
le32_to_cpu(slot_ctx->dev_state) & DEV_ADDR_MASK);
+out:
+ mutex_unlock(&xhci->mutex);
kfree(command);
- return 0;
+ return ret;
}
int xhci_address_device(struct usb_hcd *hcd, struct usb_device *udev)
@@ -4855,6 +4865,7 @@ int xhci_gen_setup(struct usb_hcd *hcd, xhci_get_quirks_t get_quirks)
return 0;
}
+ mutex_init(&xhci->mutex);
xhci->cap_regs = hcd->regs;
xhci->op_regs = hcd->regs +
HC_LENGTH(readl(&xhci->cap_regs->hc_capbase));
diff --git a/drivers/usb/host/xhci.h b/drivers/usb/host/xhci.h
index ea75e8ccd3c1..6977f8491fa7 100644
--- a/drivers/usb/host/xhci.h
+++ b/drivers/usb/host/xhci.h
@@ -1497,6 +1497,8 @@ struct xhci_hcd {
struct list_head lpm_failed_devs;
/* slot enabling and address device helpers */
+ /* these are not thread safe so use mutex */
+ struct mutex mutex;
struct completion addr_dev;
int slot_id;
/* For USB 3.0 LPM enable/disable. */
--
2.4.1
--
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