Hello Steve!
On 01.07.2025 02:53, Steven Rostedt wrote:
> Make unwind_deferred_request() NMI-safe so tracers in NMI context can
> call it and safely request a user space stacktrace when the task exits.
> diff --git a/include/linux/unwind_deferred_types.h b/include/linux/unwind_deferred_types.h
> @@ -2,6 +2,9 @@
> #ifndef _LINUX_UNWIND_USER_DEFERRED_TYPES_H
> #define _LINUX_UNWIND_USER_DEFERRED_TYPES_H
>
> +#include <asm/local64.h>
> +#include <asm/local.h>
This creates the following circular dependency, that breaks the build on
s390 as follows, whenever local64.h is included first, so that local64_t
is not yet defined when unwind_deferred_types.h gets included down the
line:
Circular dependency:
include/linux/unwind_deferred_types.h
arch/<arch>/include/generated/asm/local64.h
include/asm-generic/local64.h
include/linux/percpu.h
include/linux/sched.h
include/linux/unwind_deferred_types.h
Compile error on s390:
CC net/ipv4/proc.o
In file included from ./include/linux/sched.h:49,
from ./include/linux/percpu.h:12,
from ./include/asm-generic/local64.h:5,
from ./arch/s390/include/generated/asm/local64.h:1,
from ./include/linux/u64_stats_sync.h:71,
from ./include/net/snmp.h:47,
from ./include/net/netns/mib.h:5,
from ./include/net/net_namespace.h:17,
from net/ipv4/proc.c:31:
./include/linux/unwind_deferred_types.h:17:9: error: unknown type name ‘local64_t’; did you mean ‘local_t’?
17 | local64_t timestamp;
| ^~~~~~~~~
| local_t
Reason it fails on s390:
net/ipv4/proc.c
+- include/net/net_namespace.h
+- include/net/netns/mib.h
+- include/net/snmp.h
+- include/linux/u64_stats_sync.h
+- arch/s390/include/generated/asm/local64.h <-- ISSUE: local64.h gets included before unwind_deferred_types.h
+- include/asm-generic/local64.h
+- include/linux/percpu.h
+- include/linux/sched.h
+- include/linux/unwind_deferred_types.h <-- ERROR: local64_t not yet defined
Reason it does not fail on x86:
net/ipv4/proc.c
+- include/net/net_namespace.h
+- include/linux/workqueue.h
| +- include/linux/timer.h
| +- include/linux/ktime.h
| +- include/linux/jiffies.h
| +- include/linux/time.h
| +- include/linux/time32.h
| +- include/linux/timex.h
| +- arch/x86/include/asm/timex.h
| +- arch/x86/include/asm/tsc.h
| +- arch/x86/include/asm/msr.h
| +- include/linux/percpu.h
| +- include/linux/sched.h
| +- include/linux/unwind_deferred_types.h <-- OK: unwind_deferred_types.h gets included before local64.h
| +- arch/x86/include/generated/asm/local64.h
| +- include/asm-generic/local64.h
| [ +- include/linux/percpu.h ]
+- include/net/netns/mib.h
+- include/net/snmp.h
+- include/linux/u64_stats_sync.h
+- arch/x86/include/generated/asm/local64.h <-- OK: local64.h comes after unwind_deferred_types.h
[ +- include/asm-generic/local64.h ]
[ +- include/linux/percpu.h ]
[ +- include/linux/sched.h ]
[ +- include/linux/unwind_deferred_types.h ]
My colleague Heiko Carstens (on Cc) suggested the following potential fix
that breaks the circular dependency, provided local[64].h does not ever
need percpu.h. At least I verified that defconfig x86 and s390 builds
still work.
diff --git a/include/asm-generic/local.h b/include/asm-generic/local.h
index 7f97018df66f..3e7ce6a9e18e 100644
--- a/include/asm-generic/local.h
+++ b/include/asm-generic/local.h
@@ -2,7 +2,6 @@
#ifndef _ASM_GENERIC_LOCAL_H
#define _ASM_GENERIC_LOCAL_H
-#include <linux/percpu.h>
#include <linux/atomic.h>
#include <asm/types.h>
diff --git a/include/asm-generic/local64.h b/include/asm-generic/local64.h
index 14963a7a6253..1f9af89916cb 100644
--- a/include/asm-generic/local64.h
+++ b/include/asm-generic/local64.h
@@ -2,7 +2,6 @@
#ifndef _ASM_GENERIC_LOCAL64_H
#define _ASM_GENERIC_LOCAL64_H
-#include <linux/percpu.h>
#include <asm/types.h>
> +
> struct unwind_cache {
> unsigned int nr_entries;
> unsigned long entries[];
> @@ -10,8 +13,8 @@ struct unwind_cache {
> struct unwind_task_info {
> struct unwind_cache *cache;
> struct callback_head work;
> - u64 timestamp;
> - int pending;
> + local64_t timestamp;
> + local_t pending;
> };
>
> #endif /* _LINUX_UNWIND_USER_DEFERRED_TYPES_H */
Regards,
Jens
--
Jens Remus
Linux on Z Development (D3303)
+49-7031-16-1128 Office
jremus@xxxxxxxxxx
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