static struct ins_ops *powerpc__associate_instruction_ops(struct arch *arch, const char *name)
{
int i;
struct ins_ops *ops;
/*
* - Interested only if instruction starts with 'b'.
* - Few start with 'b', but aren't branch instructions.
*/
if (name[0] != 'b' ||
!strncmp(name, "bcd", 3) ||
!strncmp(name, "brinc", 5) ||
!strncmp(name, "bper", 4))
return NULL;
ops = &jump_ops;
i = strlen(name) - 1;
if (i < 0)
return NULL;
/* ignore optional hints at the end of the instructions */
if (name[i] == '+' || name[i] == '-')
i--;
if (name[i] == 'l' || (name[i] == 'a' && name[i-1] == 'l')) {
/*
* if the instruction ends up with 'l' or 'la', then
* those are considered 'calls' since they update LR.
* ... except for 'bnl' which is branch if not less than
* and the absolute form of the same.
*/
if (strcmp(name, "bnl") && strcmp(name, "bnl+") &&
strcmp(name, "bnl-") && strcmp(name, "bnla") &&
strcmp(name, "bnla+") && strcmp(name, "bnla-"))
ops = &call_ops;
}
if (name[i] == 'r' && name[i-1] == 'l')
/*
* instructions ending with 'lr' are considered to be
* return instructions
*/
ops = &ret_ops;
arch__associate_ins_ops(arch, name, ops);
return ops;
}
static int powerpc__annotate_init(struct arch *arch)
{
if (!arch->initialized) {
arch->initialized = true;
arch->associate_instruction_ops = powerpc__associate_instruction_ops;
arch->objdump.comment_char = '#';
}
return 0;
}
>
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+