/* register 01h */
#define CS4362A_PDN 0x01
#define CS4362A_DAC1_DIS 0x02
#define CS4362A_DAC2_DIS 0x04
#define CS4362A_DAC3_DIS 0x08
#define CS4362A_MCLKDIV 0x20
#define CS4362A_FREEZE 0x40
#define CS4362A_CPEN 0x80
/* register 02h */
#define CS4362A_DIF_MASK 0x70
#define CS4362A_DIF_LJUST 0x00
#define CS4362A_DIF_I2S 0x10
#define CS4362A_DIF_RJUST_16 0x20
#define CS4362A_DIF_RJUST_24 0x30
#define CS4362A_DIF_RJUST_20 0x40
#define CS4362A_DIF_RJUST_18 0x50
/* register 03h */
#define CS4362A_MUTEC_MASK 0x03
#define CS4362A_MUTEC_6 0x00
#define CS4362A_MUTEC_1 0x01
#define CS4362A_MUTEC_3 0x03
#define CS4362A_AMUTE 0x04
#define CS4362A_MUTEC_POL 0x08
#define CS4362A_RMP_UP 0x10
#define CS4362A_SNGLVOL 0x20
#define CS4362A_ZERO_CROSS 0x40
#define CS4362A_SOFT_RAMP 0x80
/* register 04h */
#define CS4362A_RMP_DN 0x01
#define CS4362A_DEM_MASK 0x06
#define CS4362A_DEM_NONE 0x00
#define CS4362A_DEM_44100 0x02
#define CS4362A_DEM_48000 0x04
#define CS4362A_DEM_32000 0x06
#define CS4362A_FILT_SEL 0x10
/* register 05h */
#define CS4362A_INV_A1 0x01
#define CS4362A_INV_B1 0x02
#define CS4362A_INV_A2 0x04
#define CS4362A_INV_B2 0x08
#define CS4362A_INV_A3 0x10
#define CS4362A_INV_B3 0x20
/* register 06h */
#define CS4362A_FM_MASK 0x03
#define CS4362A_FM_SINGLE 0x00
#define CS4362A_FM_DOUBLE 0x01
#define CS4362A_FM_QUAD 0x02
#define CS4362A_FM_DSD 0x03
#define CS4362A_ATAPI_MASK 0x7c
#define CS4362A_ATAPI_B_MUTE 0x00
#define CS4362A_ATAPI_B_R 0x04
#define CS4362A_ATAPI_B_L 0x08
#define CS4362A_ATAPI_B_LR 0x0c
#define CS4362A_ATAPI_A_MUTE 0x00
#define CS4362A_ATAPI_A_R 0x10
#define CS4362A_ATAPI_A_L 0x20
#define CS4362A_ATAPI_A_LR 0x30
#define CS4362A_ATAPI_MIX_LR_VOL 0x40
#define CS4362A_A_EQ_B 0x80
/* register 07h */
#define CS4362A_VOL_MASK 0x7f
#define CS4362A_MUTE 0x80
/* register 08h: like 07h */
/* registers 09h..0Bh: like 06h..08h */
/* registers 0Ch..0Eh: like 06h..08h */
/* register 12h */
#define CS4362A_REV_MASK 0x07
#define CS4362A_PART_MASK 0xf8
#define CS4362A_PART_CS4362A 0x50
/cgit.cgi/linux/net-next.git/commit/sound/soc/codecs/ak4535.c?h=nds-private-remove&id=966d2b04e070bc040319aaebfec09e0144dc3341'>commitdiff
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+