Currently, the max_loop commandline argument can be used to specify how
many loop block devices are created at init time. If it is not
specified on the commandline, CONFIG_BLK_DEV_LOOP_MIN_COUNT loop block
devices will be created.
The max_loop commandline argument can be used to override the value of
CONFIG_BLK_DEV_LOOP_MIN_COUNT. However, when max_loop is set to 0
through the commandline, the current logic treats it as if it had not
been set, and creates CONFIG_BLK_DEV_LOOP_MIN_COUNT devices anyway.
Fix this by starting max_loop off as set to CONFIG_BLK_DEV_LOOP_MIN_COUNT.
This preserves the intended behavior of creating
CONFIG_BLK_DEV_LOOP_MIN_COUNT loop block devices if the max_loop
commandline parameter is not specified, and allowing max_loop to
be respected for all values, including 0.
This allows environments that can create all of their required loop
block devices on demand to not have to unnecessarily preallocate loop
block devices.
Fixes: 732850827450 ("remove artificial software max_loop limit")
Cc: stable(a)vger.kernel.org
Cc: Ken Chen <kenchen(a)google.com>
Signed-off-by: Isaac J. Manjarres <isaacmanjarres(a)google.com>
---
drivers/block/loop.c | 28 ++++++++++++----------------
1 file changed, 12 insertions(+), 16 deletions(-)
This is a resend because I misspelled the address for
stable(a)vger.kernel.org the first time.
--Isaac
diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index ad92192c7d61..d12d3d171ec4 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -1773,7 +1773,16 @@ static const struct block_device_operations lo_fops = {
/*
* And now the modules code and kernel interface.
*/
-static int max_loop;
+
+/*
+ * If max_loop is specified, create that many devices upfront.
+ * This also becomes a hard limit. If max_loop is not specified,
+ * create CONFIG_BLK_DEV_LOOP_MIN_COUNT loop devices at module
+ * init time. Loop devices can be requested on-demand with the
+ * /dev/loop-control interface, or be instantiated by accessing
+ * a 'dead' device node.
+ */
+static int max_loop = CONFIG_BLK_DEV_LOOP_MIN_COUNT;
module_param(max_loop, int, 0444);
MODULE_PARM_DESC(max_loop, "Maximum number of loop devices");
module_param(max_part, int, 0444);
@@ -2181,7 +2190,7 @@ MODULE_ALIAS("devname:loop-control");
static int __init loop_init(void)
{
- int i, nr;
+ int i;
int err;
part_shift = 0;
@@ -2209,19 +2218,6 @@ static int __init loop_init(void)
goto err_out;
}
- /*
- * If max_loop is specified, create that many devices upfront.
- * This also becomes a hard limit. If max_loop is not specified,
- * create CONFIG_BLK_DEV_LOOP_MIN_COUNT loop devices at module
- * init time. Loop devices can be requested on-demand with the
- * /dev/loop-control interface, or be instantiated by accessing
- * a 'dead' device node.
- */
- if (max_loop)
- nr = max_loop;
- else
- nr = CONFIG_BLK_DEV_LOOP_MIN_COUNT;
-
err = misc_register(&loop_misc);
if (err < 0)
goto err_out;
@@ -2233,7 +2229,7 @@ static int __init loop_init(void)
}
/* pre-create number of devices given by config or max_loop */
- for (i = 0; i < nr; i++)
+ for (i = 0; i < max_loop; i++)
loop_add(i);
printk(KERN_INFO "loop: module loaded\n");
--
2.39.0.rc1.256.g54fd8350bd-goog
The commit 74e7e1efdad4 (xen/netback: don't call kfree_skb() with
interrupts disabled) fixes deadlock in Linux netback driver. This seems
to be a good candidate for the stable trees. This patch didn't apply
cleanly in 5.15 kernel due to difference in function prototypes in
drivers/net/xen-netback/common.h.
Juergen Gross (1):
xen/netback: don't call kfree_skb() with interrupts disabled
drivers/net/xen-netback/common.h | 2 +-
drivers/net/xen-netback/interface.c | 6 ++++--
drivers/net/xen-netback/rx.c | 8 +++++---
3 files changed, 10 insertions(+), 6 deletions(-)
--
2.39.0.rc1.256.g54fd8350bd-goog
usb_kill_urb warranties that all the handlers are finished when it
returns, but does not protect against threads that might be handling
asynchronously the urb.
For UVC, the function uvc_ctrl_status_event_async() takes care of
control changes asynchronously.
If the code is executed in the following order:
CPU 0 CPU 1
===== =====
uvc_status_complete()
uvc_status_stop()
uvc_ctrl_status_event_work()
uvc_status_start() -> FAIL
Then uvc_status_start will keep failing and this error will be shown:
<4>[ 5.540139] URB 0000000000000000 submitted while active
drivers/usb/core/urb.c:378 usb_submit_urb+0x4c3/0x528
Let's improve the current situation, by not re-submiting the urb if
we are stopping the status event. Also process the queued work
(if any) during stop.
CPU 0 CPU 1
===== =====
uvc_status_complete()
uvc_status_stop()
uvc_status_start()
uvc_ctrl_status_event_work() -> FAIL
Hopefully, with the usb layer protection this should be enough to cover
all the cases.
Cc: stable(a)vger.kernel.org
Fixes: e5225c820c05 ("media: uvcvideo: Send a control event when a Control Change interrupt arrives")
Reviewed-by: Yunke Cao <yunkec(a)chromium.org>
Signed-off-by: Ricardo Ribalda <ribalda(a)chromium.org>
---
uvc: Fix race condition on uvc
Make sure that all the async work is finished when we stop the status urb.
To: Yunke Cao <yunkec(a)chromium.org>
To: Sergey Senozhatsky <senozhatsky(a)chromium.org>
To: Max Staudt <mstaudt(a)google.com>
To: Laurent Pinchart <laurent.pinchart(a)ideasonboard.com>
To: Mauro Carvalho Chehab <mchehab(a)kernel.org>
Cc: linux-media(a)vger.kernel.org
Cc: linux-kernel(a)vger.kernel.org
---
Changes in v3:
- Remove the patch for dev->status, makes more sense in another series, and makes
the zero day less nervous.
- Update reviewed-by (thanks Yunke!).
- Link to v2: https://lore.kernel.org/r/20221212-uvc-race-v2-0-54496cc3b8ab@chromium.org
Changes in v2:
- Add a patch for not kalloc dev->status
- Redo the logic mechanism, so it also works with suspend (Thanks Yunke!)
- Link to v1: https://lore.kernel.org/r/20221212-uvc-race-v1-0-c52e1783c31d@chromium.org
---
drivers/media/usb/uvc/uvc_ctrl.c | 3 +++
drivers/media/usb/uvc/uvc_status.c | 6 ++++++
drivers/media/usb/uvc/uvcvideo.h | 1 +
3 files changed, 10 insertions(+)
diff --git a/drivers/media/usb/uvc/uvc_ctrl.c b/drivers/media/usb/uvc/uvc_ctrl.c
index c95a2229f4fa..5160facc8e20 100644
--- a/drivers/media/usb/uvc/uvc_ctrl.c
+++ b/drivers/media/usb/uvc/uvc_ctrl.c
@@ -1442,6 +1442,9 @@ static void uvc_ctrl_status_event_work(struct work_struct *work)
uvc_ctrl_status_event(w->chain, w->ctrl, w->data);
+ if (dev->flush_status)
+ return;
+
/* Resubmit the URB. */
w->urb->interval = dev->int_ep->desc.bInterval;
ret = usb_submit_urb(w->urb, GFP_KERNEL);
diff --git a/drivers/media/usb/uvc/uvc_status.c b/drivers/media/usb/uvc/uvc_status.c
index 7518ffce22ed..09a5802dc974 100644
--- a/drivers/media/usb/uvc/uvc_status.c
+++ b/drivers/media/usb/uvc/uvc_status.c
@@ -304,10 +304,16 @@ int uvc_status_start(struct uvc_device *dev, gfp_t flags)
if (dev->int_urb == NULL)
return 0;
+ dev->flush_status = false;
return usb_submit_urb(dev->int_urb, flags);
}
void uvc_status_stop(struct uvc_device *dev)
{
+ struct uvc_ctrl_work *w = &dev->async_ctrl;
+
+ dev->flush_status = true;
usb_kill_urb(dev->int_urb);
+ if (cancel_work_sync(&w->work))
+ uvc_ctrl_status_event(w->chain, w->ctrl, w->data);
}
diff --git a/drivers/media/usb/uvc/uvcvideo.h b/drivers/media/usb/uvc/uvcvideo.h
index df93db259312..6a9b72d6789e 100644
--- a/drivers/media/usb/uvc/uvcvideo.h
+++ b/drivers/media/usb/uvc/uvcvideo.h
@@ -560,6 +560,7 @@ struct uvc_device {
struct usb_host_endpoint *int_ep;
struct urb *int_urb;
u8 *status;
+ bool flush_status;
struct input_dev *input;
char input_phys[64];
---
base-commit: 0ec5a38bf8499f403f81cb81a0e3a60887d1993c
change-id: 20221212-uvc-race-09276ea68bf8
Best regards,
--
Ricardo Ribalda <ribalda(a)chromium.org>