#
# kbuild file for usr/ - including initramfs image
#
klibcdirs:;
PHONY += klibcdirs
suffix_y = $(subst $\",,$(CONFIG_INITRAMFS_COMPRESSION))
datafile_y = initramfs_data.cpio$(suffix_y)
AFLAGS_initramfs_data.o += -DINITRAMFS_IMAGE="usr/$(datafile_y)"
# Generate builtin.o based on initramfs_data.o
obj-$(CONFIG_BLK_DEV_INITRD) := initramfs_data.o
# initramfs_data.o contains the compressed initramfs_data.cpio image.
# The image is included using .incbin, a dependency which is not
# tracked automatically.
$(obj)/initramfs_data.o: $(obj)/$(datafile_y) FORCE
#####
# Generate the initramfs cpio archive
hostprogs-y := gen_init_cpio
initramfs := $(CONFIG_SHELL) $(srctree)/scripts/gen_initramfs_list.sh
ramfs-input := $(if $(filter-out "",$(CONFIG_INITRAMFS_SOURCE)), \
$(shell echo $(CONFIG_INITRAMFS_SOURCE)),-d)
ramfs-args := \
$(if $(CONFIG_INITRAMFS_ROOT_UID), -u $(CONFIG_INITRAMFS_ROOT_UID)) \
$(if $(CONFIG_INITRAMFS_ROOT_GID), -g $(CONFIG_INITRAMFS_ROOT_GID))
# .initramfs_data.cpio.d is used to identify all files included
# in initramfs and to detect if any files are added/removed.
# Removed files are identified by directory timestamp being updated
# The dependency list is generated by gen_initramfs.sh -l
ifneq ($(wildcard $(obj)/.initramfs_data.cpio.d),)
include $(obj)/.initramfs_data.cpio.d
endif
quiet_cmd_initfs = GEN $@
cmd_initfs = $(initramfs) -o $@ $(ramfs-args) $(ramfs-input)
targets := $(datafile_y)
# do not try to update files included in initramfs
$(deps_initramfs): ;
$(deps_initramfs): klibcdirs
# We rebuild initramfs_data.cpio if:
# 1) Any included file is newer then initramfs_data.cpio
# 2) There are changes in which files are included (added or deleted)
# 3) If gen_init_cpio are newer than initramfs_data.cpio
# 4) arguments to gen_initramfs.sh changes
$(obj)/$(datafile_y): $(obj)/gen_init_cpio $(deps_initramfs) klibcdirs
$(Q)$(initramfs) -l $(ramfs-input) > $(obj)/.initramfs_data.cpio.d
$(call if_changed,initfs)
d1'>diff
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+