Re: [PATCH V2 2/2] mm/migration: Add trace events for base page and HugeTLB migrations

[Anshuman Khandual <anshuman.khandual@arm.com>]

On 1/27/22 10:22 AM, Anshuman Khandual wrote:
> 
> 
> On 1/27/22 9:37 AM, Andrew Morton wrote:
>> On Tue, 25 Jan 2022 15:58:34 +0530 Anshuman Khandual <anshuman.khandual@arm.com> wrote:
>>
>>>
>>>
>>>
>>> The following change should fix both the reported build problems.
>>>
>>> diff --git a/mm/rmap.c b/mm/rmap.c
>>> index cce5dbae07f2..cae1c46440d6 100644
>>> --- a/mm/rmap.c
>>> +++ b/mm/rmap.c
>>> @@ -76,6 +76,7 @@
>>>  
>>>  #include <asm/tlbflush.h>
>>>  
>>> +#define CREATE_TRACE_POINTS
>>>  #include <trace/events/tlb.h>
>>>  #include <trace/events/migrate.h>
>>
>> My x86_64 allmodconfig is unhappy.
>>
>> lib/strncpy_from_user.o: warning: objtool: strncpy_from_user()+0x129: call to do_strncpy_from_user() with UACCESS enabled
>> lib/strnlen_user.o: warning: objtool: strnlen_user()+0xc9: call to do_strnlen_user() with UACCESS enabled
>> /opt/crosstool/gcc-10.3.0-nolibc/x86_64-linux/bin/x86_64-linux-ld: mm/rmap.o:(.data+0x13e0): multiple definition of `__SCK__tp_func_tlb_flush'; arch/x86/mm/init.o:(.data+0x980): first defined here
>> /opt/crosstool/gcc-10.3.0-nolibc/x86_64-linux/bin/x86_64-linux-ld: mm/rmap.o: in function `__traceiter_tlb_flush':
>> (.text+0x0): multiple definition of `__traceiter_tlb_flush'; arch/x86/mm/init.o:(.text+0x0): first defined here
>> /opt/crosstool/gcc-10.3.0-nolibc/x86_64-linux/bin/x86_64-linux-ld: mm/rmap.o:(__tracepoints+0x180): multiple definition of `__tracepoint_tlb_flush'; arch/x86/mm/init.o:(__tracepoints+0x0): first defined here
>> /opt/crosstool/gcc-10.3.0-nolibc/x86_64-linux/bin/x86_64-linux-ld: mm/rmap.o: in function `__SCT__tp_func_tlb_flush':
>> (.static_call.text+0x0): multiple definition of `__SCT__tp_func_tlb_flush'; arch/x86/mm/init.o:(.static_call.text+0x0): first defined here
>> /opt/crosstool/gcc-10.3.0-nolibc/x86_64-linux/bin/x86_64-linux-ld: mm/migrate.o: in function `__SCT__tp_func_mm_migrate_pages':
>> (.static_call.text+0x0): multiple definition of `__SCT__tp_func_mm_migrate_pages'; mm/rmap.o:(.static_call.text+0x8): first defined here
>> /opt/crosstool/gcc-10.3.0-nolibc/x86_64-linux/bin/x86_64-linux-ld: mm/migrate.o:(.data+0x13a0): multiple definition of `__SCK__tp_func_remove_migration_pte'; mm/rmap.o:(.data+0xfe0): first defined here
>> /opt/crosstool/gcc-10.3.0-nolibc/x86_64-linux/bin/x86_64-linux-ld: mm/migrate.o: in function `__traceiter_set_migration_pte':
>> (.text+0x140): multiple definition of `__traceiter_set_migration_pte'; mm/rmap.o:(.text+0x1c0): first defined here
>> /opt/crosstool/gcc-10.3.0-nolibc/x86_64-linux/bin/x86_64-linux-ld: mm/migrate.o:(__tracepoints+0x120): multiple definition of `__tracepoint_mm_migrate_pages'; mm/rmap.o:(__tracepoints+0x120): first defined here
>> /opt/crosstool/gcc-10.3.0-nolibc/x86_64-linux/bin/x86_64-linux-ld: mm/migrate.o: in function `__traceiter_mm_migrate_pages':
>> (.text+0x0): multiple definition of `__traceiter_mm_migrate_pages'; mm/rmap.o:(.text+0x80): first defined here
>> /opt/crosstool/gcc-10.3.0-nolibc/x86_64-linux/bin/x86_64-linux-ld: mm/migrate.o: in function `__SCT__tp_func_mm_migrate_pages_start':
>> (.static_call.text+0x8): multiple definition of `__SCT__tp_func_mm_migrate_pages_start'; mm/rmap.o:(.static_call.text+0x10): first defined here
>> /opt/crosstool/gcc-10.3.0-nolibc/x86_64-linux/bin/x86_64-linux-ld: mm/migrate.o:(.data+0x1420): multiple definition of `__SCK__tp_func_mm_migrate_pages_start'; mm/rmap.o:(.data+0x1060): first defined here
>> /opt/crosstool/gcc-10.3.0-nolibc/x86_64-linux/bin/x86_64-linux-ld: mm/migrate.o:(.data+0x1460): multiple definition of `__SCK__tp_func_mm_migrate_pages'; mm/rmap.o:(.data+0x10a0): first defined here
>> /opt/crosstool/gcc-10.3.0-nolibc/x86_64-linux/bin/x86_64-linux-ld: mm/migrate.o: in function `__traceiter_mm_migrate_pages_start':
>> (.text+0xc0): multiple definition of `__traceiter_mm_migrate_pages_start'; mm/rmap.o:(.text+0x140): first defined here
>> /opt/crosstool/gcc-10.3.0-nolibc/x86_64-linux/bin/x86_64-linux-ld: mm/migrate.o: in function `__SCT__tp_func_remove_migration_pte':
>> (.static_call.text+0x18): multiple definition of `__SCT__tp_func_remove_migration_pte'; mm/rmap.o:(.static_call.text+0x20): first defined here
>> /opt/crosstool/gcc-10.3.0-nolibc/x86_64-linux/bin/x86_64-linux-ld: mm/migrate.o:(__tracepoints+0x60): multiple definition of `__tracepoint_set_migration_pte'; mm/rmap.o:(__tracepoints+0x60): first defined here
>> /opt/crosstool/gcc-10.3.0-nolibc/x86_64-linux/bin/x86_64-linux-ld: mm/migrate.o:(__tracepoints+0x0): multiple definition of `__tracepoint_remove_migration_pte'; mm/rmap.o:(__tracepoints+0x0): first defined here
>> /opt/crosstool/gcc-10.3.0-nolibc/x86_64-linux/bin/x86_64-linux-ld: mm/migrate.o: in function `__traceiter_remove_migration_pte':
>> (.text+0x1c0): multiple definition of `__traceiter_remove_migration_pte'; mm/rmap.o:(.text+0x240): first defined here
>> /opt/crosstool/gcc-10.3.0-nolibc/x86_64-linux/bin/x86_64-linux-ld: mm/migrate.o: in function `__SCT__tp_func_set_migration_pte':
>> (.static_call.text+0x10): multiple definition of `__SCT__tp_func_set_migration_pte'; mm/rmap.o:(.static_call.text+0x18): first defined here
>> /opt/crosstool/gcc-10.3.0-nolibc/x86_64-linux/bin/x86_64-linux-ld: mm/migrate.o:(.data+0x13e0): multiple definition of `__SCK__tp_func_set_migration_pte'; mm/rmap.o:(.data+0x1020): first defined here
>> /opt/crosstool/gcc-10.3.0-nolibc/x86_64-linux/bin/x86_64-linux-ld: mm/migrate.o:(__tracepoints+0xc0): multiple definition of `__tracepoint_mm_migrate_pages_start'; mm/rmap.o:(__tracepoints+0xc0): first defined here
>> make: *** [vmlinux] Error 1
>>
> 
> This also seems to be a problem for existing trace points as well like tlb_flush
> <events/tlb.h>, mm_migrate_pages_start and mm_migrate_pages <events/migrate.h>.
> Is there some cyclic dependency ? Regardless, I can recreate the build problem.
> Will look into it.

CREATE_TRACE_POINTS should be defined just once, even if the corresponding trace
header file is included in multiple C files. mm/rmap.c is a better place to have
CREATE_TRACE_POINTS defined as it gets built always with CONFIG_MMU. Because the
file mm/rmap.c now includes both <trace/events/migrate.h> and <trace/events/tlb.h>
, all existing CREATE_TRACE_POINTS (including inside platforms) for them need to
be dropped. A similar problem got created for <trace/events/thp.h> on powerpc as
well, after the first patch.

The following patch here fixes this problem. But I will do some more testing and
respin the series.

diff --git a/arch/powerpc/mm/book3s64/trace.c b/arch/powerpc/mm/book3s64/trace.c
index b86e7b906257..ccd64b5e6cac 100644
--- a/arch/powerpc/mm/book3s64/trace.c
+++ b/arch/powerpc/mm/book3s64/trace.c
@@ -3,6 +3,5 @@
  * This file is for defining trace points and trace related helpers.
  */
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
-#define CREATE_TRACE_POINTS
 #include <trace/events/thp.h>
 #endif
diff --git a/arch/x86/mm/init.c b/arch/x86/mm/init.c
index 4ba024d5b63a..d8cfce221275 100644
--- a/arch/x86/mm/init.c
+++ b/arch/x86/mm/init.c
@@ -31,7 +31,6 @@
  * We need to define the tracepoints somewhere, and tlb.c
  * is only compiled when SMP=y.
  */
-#define CREATE_TRACE_POINTS
 #include <trace/events/tlb.h>
 
 #include "mm_internal.h"
diff --git a/mm/migrate.c b/mm/migrate.c
index 253dc5812949..79e3a553923a 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -54,7 +54,6 @@
 
 #include <asm/tlbflush.h>
 
-#define CREATE_TRACE_POINTS
 #include <trace/events/migrate.h>
 
 #include "internal.h"