Hi,
with linux kernel v6.8-rc2-RT and the following file as testcase
----->8--------
#include <linux/spinlock.h>
#include <linux/local_lock.h>
struct per_cpu_struct {
local_lock_t lock;
unsigned int something;
};
static DEFINE_PER_CPU(struct per_cpu_struct, per_cpu_struct) = {
.lock = INIT_LOCAL_LOCK(lock),
};
DEFINE_GUARD(ll_lock, local_lock_t __percpu*,
local_lock(_T),
local_unlock(_T))
void function(void);
void function(void)
{
struct per_cpu_struct *pcs = this_cpu_ptr(&per_cpu_struct);
guard(ll_lock)(&per_cpu_struct.lock);
pcs->something++;
}
-----8<--------
compiling and running pahole afterwards:
| make kernel/pahole-tc.o && pahole -J --btf_gen_floats -j --lang_exclude=rust kernel/pahole-tc.o
| CC kernel/pahole-tc.o
| error: found variable 'per_cpu_struct' in CU 'kernel/pahole-tc.c' that has void type
This doesn't look good. If I swap the order of "lock" and "something"
within per_cpu_struct then it goes away.
The dwarf/die object it complains about has only DW_AT_abstract_origin
and DW_AT_location set.
At this point I am not sure if gcc wrongly created the dwarf information
or of pahole accidentally matches the internal local_lock_t member as
per_cpu_struct because it starts the same address.
>From dumpwarf the problematic entry is:
| 0x0000085b: DW_TAG_variable
| DW_AT_abstract_origin (0x0000099e "t")
| DW_AT_location (DW_OP_addr 0x0, DW_OP_stack_value)
which looks slightly different in the good case:
| 0x00000852: DW_TAG_variable
| DW_AT_abstract_origin (0x00000980 "t")
| DW_AT_location (0x00000040:
| [0x0000000000000046, 0x000000000000005b): DW_OP_reg3 RBX
| [0x000000000000005b, 0x0000000000000061): DW_OP_addr 0x0, DW_OP_stack_value)
| DW_AT_GNU_locviews (0x0000003c)
I made an archive with c file, the compiled version in bad and good case
(swapped the first two members), the dumpwarf output and uploaded to
https://breakpoint.cc/pahole-tc.tar.xz
Sebastian
