Juergen Gross 1a3fc2c402 xen: avoid deadlock in xenbus driver ... There has been a report about a deadlock in the xenbus driver: [ 247.979498] ====================================================== [ 247.985688] WARNING: possible circular locking dependency detected [ 247.991882] 4.12.0-rc4-00022-gc4b25c0 #575 Not tainted [ 247.997040] ------------------------------------------------------ [ 248.003232] xenbus/91 is trying to acquire lock: [ 248.007875] (&u->msgbuffer_mutex){+.+.+.}, at: [<ffff00000863e904>] xenbus_dev_queue_reply+0x3c/0x230 [ 248.017163] [ 248.017163] but task is already holding lock: [ 248.023096] (xb_write_mutex){+.+...}, at: [<ffff00000863a940>] xenbus_thread+0x5f0/0x798 [ 248.031267] [ 248.031267] which lock already depends on the new lock. [ 248.031267] [ 248.039615] [ 248.039615] the existing dependency chain (in reverse order) is: [ 248.047176] [ 248.047176] -> #1 (xb_write_mutex){+.+...}: [ 248.052943] __lock_acquire+0x1728/0x1778 [ 248.057498] lock_acquire+0xc4/0x288 [ 248.061630] __mutex_lock+0x84/0x868 [ 248.065755] mutex_lock_nested+0x3c/0x50 [ 248.070227] xs_send+0x164/0x1f8 [ 248.074015] xenbus_dev_request_and_reply+0x6c/0x88 [ 248.079427] xenbus_file_write+0x260/0x420 [ 248.084073] __vfs_write+0x48/0x138 [ 248.088113] vfs_write+0xa8/0x1b8 [ 248.091983] SyS_write+0x54/0xb0 [ 248.095768] el0_svc_naked+0x24/0x28 [ 248.099897] [ 248.099897] -> #0 (&u->msgbuffer_mutex){+.+.+.}: [ 248.106088] print_circular_bug+0x80/0x2e0 [ 248.110730] __lock_acquire+0x1768/0x1778 [ 248.115288] lock_acquire+0xc4/0x288 [ 248.119417] __mutex_lock+0x84/0x868 [ 248.123545] mutex_lock_nested+0x3c/0x50 [ 248.128016] xenbus_dev_queue_reply+0x3c/0x230 [ 248.133005] xenbus_thread+0x788/0x798 [ 248.137306] kthread+0x110/0x140 [ 248.141087] ret_from_fork+0x10/0x40 It is rather easy to avoid by dropping xb_write_mutex before calling xenbus_dev_queue_reply(). Fixes: fd8aa9095a ("xen: optimize xenbus driver for multiple concurrent xenstore accesses"). Cc: <stable@vger.kernel.org> # 4.11 Reported-by: Andre Przywara <andre.przywara@arm.com> Signed-off-by: Juergen Gross <jgross@suse.com> Tested-by: Andre Przywara <andre.przywara@arm.com> Signed-off-by: Juergen Gross <jgross@suse.com>		2017-06-25 13:11:22 +02:00
..
events	xen-evtchn: Bind dyn evtchn:qemu-dm interrupt to next online VCPU	2017-06-13 15:30:27 +02:00
xen-pciback	xen: modify xenstore watch event interface	2017-02-09 11:26:49 -05:00
xenbus	xen: avoid deadlock in xenbus driver	2017-06-25 13:11:22 +02:00
xenfs	fs: constify tree_descr arrays passed to simple_fill_super()	2017-04-26 23:54:06 -04:00
acpi.c
arm-device.c	Xen: ARM: Zero reserved fields of xatp before making hypervisor call	2017-01-03 10:06:13 -08:00
balloon.c	xen/balloon: decorate PV-only parts with #ifdef CONFIG_XEN_PV	2017-05-02 11:09:56 +02:00
biomerge.c
cpu_hotplug.c	xen: modify xenstore watch event interface	2017-02-09 11:26:49 -05:00
dbgp.c
efi.c	xen: Implement EFI reset_system callback	2017-05-02 12:06:50 +02:00
evtchn.c	xen-evtchn: Bind dyn evtchn:qemu-dm interrupt to next online VCPU	2017-06-13 15:30:27 +02:00
fallback.c
features.c
gntalloc.c	xen: set error code on failures	2016-12-08 07:53:50 +01:00
gntdev.c	drivers, xen: convert grant_map.users from atomic_t to refcount_t	2017-03-13 12:45:18 -04:00
grant-table.c	xen/pvh: Initialize grant table for PVH guests	2017-02-07 08:07:01 -05:00
Kconfig
Makefile
manage.c	xen: don't print error message in case of missing Xenstore entry	2017-06-07 09:48:02 +02:00
mcelog.c
pci.c
pcpu.c
platform-pci.c	xen: Revert commits da72ff5bfc and 72a9b18629	2017-05-02 11:18:05 +02:00
preempt.c
privcmd.c	mm, fs: reduce fault, page_mkwrite, and pfn_mkwrite to take only vmf	2017-02-24 17:46:54 -08:00
privcmd.h
swiotlb-xen.c	xen/arm,arm64: rename __generic_dma_ops to xen_get_dma_ops	2017-05-02 11:14:47 +02:00
sys-hypervisor.c	xen: add sysfs node for hypervisor build id	2017-06-15 08:50:37 +02:00
time.c
tmem.c
xen-acpi-cpuhotplug.c
xen-acpi-memhotplug.c
xen-acpi-pad.c
xen-acpi-processor.c	xen/acpi: upload PM state from init-domain to Xen	2017-03-23 12:00:02 -04:00
xen-balloon.c	xen: modify xenstore watch event interface	2017-02-09 11:26:49 -05:00
xen-scsiback.c
xen-selfballoon.c
xen-stub.c
xlate_mmu.c