#
# Makefile for the kernel USB device drivers.
#
# Object files in subdirectories
obj-$(CONFIG_USB) += core/
obj-$(CONFIG_USB_SUPPORT) += phy/
obj-$(CONFIG_USB_DWC3) += dwc3/
obj-$(CONFIG_USB_DWC2) += dwc2/
obj-$(CONFIG_USB_ISP1760) += isp1760/
obj-$(CONFIG_USB_MON) += mon/
obj-$(CONFIG_USB_MTU3) += mtu3/
obj-$(CONFIG_PCI) += host/
obj-$(CONFIG_USB_EHCI_HCD) += host/
obj-$(CONFIG_USB_ISP116X_HCD) += host/
obj-$(CONFIG_USB_OHCI_HCD) += host/
obj-$(CONFIG_USB_UHCI_HCD) += host/
obj-$(CONFIG_USB_FHCI_HCD) += host/
obj-$(CONFIG_USB_XHCI_HCD) += host/
obj-$(CONFIG_USB_SL811_HCD) += host/
obj-$(CONFIG_USB_ISP1362_HCD) += host/
obj-$(CONFIG_USB_U132_HCD) += host/
obj-$(CONFIG_USB_R8A66597_HCD) += host/
obj-$(CONFIG_USB_HWA_HCD) += host/
obj-$(CONFIG_USB_IMX21_HCD) += host/
obj-$(CONFIG_USB_FSL_USB2) += host/
obj-$(CONFIG_USB_FOTG210_HCD) += host/
obj-$(CONFIG_USB_MAX3421_HCD) += host/
obj-$(CONFIG_USB_C67X00_HCD) += c67x00/
obj-$(CONFIG_USB_WUSB) += wusbcore/
obj-$(CONFIG_USB_ACM) += class/
obj-$(CONFIG_USB_PRINTER) += class/
obj-$(CONFIG_USB_WDM) += class/
obj-$(CONFIG_USB_TMC) += class/
obj-$(CONFIG_USB_STORAGE) += storage/
obj-$(CONFIG_USB) += storage/
obj-$(CONFIG_USB_MDC800) += image/
obj-$(CONFIG_USB_MICROTEK) += image/
obj-$(CONFIG_USB_SERIAL) += serial/
obj-$(CONFIG_USB) += misc/
obj-$(CONFIG_EARLY_PRINTK_DBGP) += early/
obj-$(CONFIG_USB_ATM) += atm/
obj-$(CONFIG_USB_SPEEDTOUCH) += atm/
obj-$(CONFIG_USB_MUSB_HDRC) += musb/
obj-$(CONFIG_USB_CHIPIDEA) += chipidea/
obj-$(CONFIG_USB_RENESAS_USBHS) += renesas_usbhs/
obj-$(CONFIG_USB_GADGET) += gadget/
obj-$(CONFIG_USB_COMMON) += common/
obj-$(CONFIG_USBIP_CORE) += usbip/
4e070bc040319aaebfec09e0144dc3341'>refslogtreecommitdiff
percpu-refcount: fix reference leak during percpu-atomic transition
percpu_ref_tryget() and percpu_ref_tryget_live() should return
"true" IFF they acquire a reference. But the return value from
atomic_long_inc_not_zero() is a long and may have high bits set,
e.g. PERCPU_COUNT_BIAS, and the return value of the tryget routines
is bool so the reference may actually be acquired but the routines
return "false" which results in a reference leak since the caller
assumes it does not need to do a corresponding percpu_ref_put().
This was seen when performing CPU hotplug during I/O, as hangs in
blk_mq_freeze_queue_wait where percpu_ref_kill (blk_mq_freeze_queue_start)
raced with percpu_ref_tryget (blk_mq_timeout_work).
Sample stack trace:
__switch_to+0x2c0/0x450
__schedule+0x2f8/0x970
schedule+0x48/0xc0
blk_mq_freeze_queue_wait+0x94/0x120
blk_mq_queue_reinit_work+0xb8/0x180
blk_mq_queue_reinit_prepare+0x84/0xa0
cpuhp_invoke_callback+0x17c/0x600
cpuhp_up_callbacks+0x58/0x150
_cpu_up+0xf0/0x1c0
do_cpu_up+0x120/0x150
cpu_subsys_online+0x64/0xe0
device_online+0xb4/0x120
online_store+0xb4/0xc0
dev_attr_store+0x68/0xa0
sysfs_kf_write+0x80/0xb0
kernfs_fop_write+0x17c/0x250
__vfs_write+0x6c/0x1e0
vfs_write+0xd0/0x270
SyS_write+0x6c/0x110
system_call+0x38/0xe0
Examination of the queue showed a single reference (no PERCPU_COUNT_BIAS,
and __PERCPU_REF_DEAD, __PERCPU_REF_ATOMIC set) and no requests.
However, conditions at the time of the race are count of PERCPU_COUNT_BIAS + 0
and __PERCPU_REF_DEAD and __PERCPU_REF_ATOMIC set.
The fix is to make the tryget routines use an actual boolean internally instead
of the atomic long result truncated to a int.
Fixes: e625305b3907 percpu-refcount: make percpu_ref based on longs instead of ints
Link: https://bugzilla.kernel.org/show_bug.cgi?id=190751
Signed-off-by: Douglas Miller <dougmill@linux.vnet.ibm.com>
Reviewed-by: Jens Axboe <axboe@fb.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Fixes: e625305b3907 ("percpu-refcount: make percpu_ref based on longs instead of ints")
Cc: stable@vger.kernel.org # v3.18+