Define GEN_AS_CONST_HEADERS when generating header files [BZ #22792]

Message ID 20180208175818.GA8519@gmail.com
State New
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  • Define GEN_AS_CONST_HEADERS when generating header files [BZ #22792]
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Commit Message

H.J. Lu Feb. 8, 2018, 5:58 p.m.
Glibc build generates header files to define constants from special .sym
files.  If a .sym file includes the same header file which it generates,
it leads to circular dependency.  Define GEN_AS_CONST_HEADERS when
generating header files to avoid circular dependency.

<tcb-offsets.h> is needed for i686 and it isn't needed for x86-64 at
least since glibc 2.23.

Tested on i686 and x86-64.

OK for trunk?

H.J.
---
	[BZ #22792]
	* Makerules ($(common-objpfx)%.h): Pass -DGEN_AS_CONST_HEADERS
	to $(CC).
	* sysdeps/unix/sysv/linux/i386/lowlevellock.h: Include
	<tcb-offsets.h> only if GEN_AS_CONST_HEADERS isn't defined.
	* sysdeps/unix/sysv/linux/x86_64/lowlevellock.h: Don't include
	<tcb-offsets.h>.
---
 Makerules                                     | 4 +++-
 sysdeps/unix/sysv/linux/i386/lowlevellock.h   | 4 +++-
 sysdeps/unix/sysv/linux/x86_64/lowlevellock.h | 1 -
 3 files changed, 6 insertions(+), 3 deletions(-)

Comments

Florian Weimer Feb. 21, 2018, 7:09 a.m. | #1
On 02/08/2018 06:58 PM, H.J. Lu wrote:
> 	[BZ #22792]
> 	* Makerules ($(common-objpfx)%.h): Pass -DGEN_AS_CONST_HEADERS
> 	to $(CC).
> 	* sysdeps/unix/sysv/linux/i386/lowlevellock.h: Include
> 	<tcb-offsets.h> only if GEN_AS_CONST_HEADERS isn't defined.
> 	* sysdeps/unix/sysv/linux/x86_64/lowlevellock.h: Don't include
> 	<tcb-offsets.h>.

It looks to me that a cleaner fix would be to move the definition of the 
TCB types to a separate header.

The circular dependency is just a cosmetic warning from make, right?

Thanks,
Florian
H.J. Lu Feb. 21, 2018, 3:40 p.m. | #2
On Tue, Feb 20, 2018 at 11:09 PM, Florian Weimer <fweimer@redhat.com> wrote:
> On 02/08/2018 06:58 PM, H.J. Lu wrote:
>>
>>         [BZ #22792]
>>         * Makerules ($(common-objpfx)%.h): Pass -DGEN_AS_CONST_HEADERS
>>         to $(CC).
>>         * sysdeps/unix/sysv/linux/i386/lowlevellock.h: Include
>>         <tcb-offsets.h> only if GEN_AS_CONST_HEADERS isn't defined.
>>         * sysdeps/unix/sysv/linux/x86_64/lowlevellock.h: Don't include
>>         <tcb-offsets.h>.
>
>
> It looks to me that a cleaner fix would be to move the definition of the TCB
> types to a separate header.

I will take a look.

> The circular dependency is just a cosmetic warning from make, right?

It depends on how unlucky you are.  In one case on a many-core machine
with make -j60, I had to kill glibc build since it never stopped.
H.J. Lu Feb. 21, 2018, 5:19 p.m. | #3
On Wed, Feb 21, 2018 at 7:40 AM, H.J. Lu <hjl.tools@gmail.com> wrote:
> On Tue, Feb 20, 2018 at 11:09 PM, Florian Weimer <fweimer@redhat.com> wrote:
>> On 02/08/2018 06:58 PM, H.J. Lu wrote:
>>>
>>>         [BZ #22792]
>>>         * Makerules ($(common-objpfx)%.h): Pass -DGEN_AS_CONST_HEADERS
>>>         to $(CC).
>>>         * sysdeps/unix/sysv/linux/i386/lowlevellock.h: Include
>>>         <tcb-offsets.h> only if GEN_AS_CONST_HEADERS isn't defined.
>>>         * sysdeps/unix/sysv/linux/x86_64/lowlevellock.h: Don't include
>>>         <tcb-offsets.h>.
>>
>>
>> It looks to me that a cleaner fix would be to move the definition of the TCB
>> types to a separate header.
>
> I will take a look.

sysdeps/i386/nptl/tcb-offsets.sym has

#include <sysdep.h>
#include <tls.h>
#include <kernel-features.h>

RESULT offsetof (struct pthread, result)
TID offsetof (struct pthread, tid)
CANCELHANDLING offsetof (struct pthread, cancelhandling)
CLEANUP_JMP_BUF offsetof (struct pthread, cleanup_jmp_buf)
MULTIPLE_THREADS_OFFSET offsetof (tcbhead_t, multiple_threads)
SYSINFO_OFFSET offsetof (tcbhead_t, sysinfo)
CLEANUP offsetof (struct pthread, cleanup)
CLEANUP_PREV offsetof (struct _pthread_cleanup_buffer, __prev)
MUTEX_FUTEX offsetof (pthread_mutex_t, __data.__lock)
POINTER_GUARD offsetof (tcbhead_t, pointer_guard)
#ifndef __ASSUME_PRIVATE_FUTEX
PRIVATE_FUTEX offsetof (tcbhead_t, private_futex)
#endif

It covers more than just tcbhead_t.  A separate header file for tcbhead_t
won't help here.

>> The circular dependency is just a cosmetic warning from make, right?
>
> It depends on how unlucky you are.  In one case on a many-core machine
> with make -j60, I had to kill glibc build since it never stopped.
>
>
> --
> H.J.
Florian Weimer Feb. 22, 2018, 3:11 p.m. | #4
On 02/21/2018 06:19 PM, H.J. Lu wrote:
> On Wed, Feb 21, 2018 at 7:40 AM, H.J. Lu <hjl.tools@gmail.com> wrote:
>> On Tue, Feb 20, 2018 at 11:09 PM, Florian Weimer <fweimer@redhat.com> wrote:
>>> On 02/08/2018 06:58 PM, H.J. Lu wrote:
>>>>
>>>>          [BZ #22792]
>>>>          * Makerules ($(common-objpfx)%.h): Pass -DGEN_AS_CONST_HEADERS
>>>>          to $(CC).
>>>>          * sysdeps/unix/sysv/linux/i386/lowlevellock.h: Include
>>>>          <tcb-offsets.h> only if GEN_AS_CONST_HEADERS isn't defined.
>>>>          * sysdeps/unix/sysv/linux/x86_64/lowlevellock.h: Don't include
>>>>          <tcb-offsets.h>.
>>>
>>>
>>> It looks to me that a cleaner fix would be to move the definition of the TCB
>>> types to a separate header.
>>
>> I will take a look.
> 
> sysdeps/i386/nptl/tcb-offsets.sym has
> 
> #include <sysdep.h>
> #include <tls.h>
> #include <kernel-features.h>
> 
> RESULT offsetof (struct pthread, result)
> TID offsetof (struct pthread, tid)
> CANCELHANDLING offsetof (struct pthread, cancelhandling)
> CLEANUP_JMP_BUF offsetof (struct pthread, cleanup_jmp_buf)
> MULTIPLE_THREADS_OFFSET offsetof (tcbhead_t, multiple_threads)
> SYSINFO_OFFSET offsetof (tcbhead_t, sysinfo)
> CLEANUP offsetof (struct pthread, cleanup)
> CLEANUP_PREV offsetof (struct _pthread_cleanup_buffer, __prev)
> MUTEX_FUTEX offsetof (pthread_mutex_t, __data.__lock)
> POINTER_GUARD offsetof (tcbhead_t, pointer_guard)
> #ifndef __ASSUME_PRIVATE_FUTEX
> PRIVATE_FUTEX offsetof (tcbhead_t, private_futex)
> #endif
> 
> It covers more than just tcbhead_t.  A separate header file for tcbhead_t
> won't help here.

Yes, it's more involved.

>>> The circular dependency is just a cosmetic warning from make, right?
>>
>> It depends on how unlucky you are.  In one case on a many-core machine
>> with make -j60, I had to kill glibc build since it never stopped.

If it fixes an actual build issue, then I think your patch is 
acceptable, although I consider it quite hackish.

But please do add a comment explaining the issue before:

+# ifndef GEN_AS_CONST_HEADERS

Thanks,
Florian
Carlos O'Donell Feb. 22, 2018, 4:46 p.m. | #5
On 02/22/2018 07:11 AM, Florian Weimer wrote:
> On 02/21/2018 06:19 PM, H.J. Lu wrote:
>> On Wed, Feb 21, 2018 at 7:40 AM, H.J. Lu <hjl.tools@gmail.com> wrote:
>>> On Tue, Feb 20, 2018 at 11:09 PM, Florian Weimer <fweimer@redhat.com> wrote:
>>>> On 02/08/2018 06:58 PM, H.J. Lu wrote:
>>>>>
>>>>>          [BZ #22792]
>>>>>          * Makerules ($(common-objpfx)%.h): Pass -DGEN_AS_CONST_HEADERS
>>>>>          to $(CC).
>>>>>          * sysdeps/unix/sysv/linux/i386/lowlevellock.h: Include
>>>>>          <tcb-offsets.h> only if GEN_AS_CONST_HEADERS isn't defined.
>>>>>          * sysdeps/unix/sysv/linux/x86_64/lowlevellock.h: Don't include
>>>>>          <tcb-offsets.h>.
>>>>
>>>>
>>>> It looks to me that a cleaner fix would be to move the definition of the TCB
>>>> types to a separate header.
>>>
>>> I will take a look.
>>
>> sysdeps/i386/nptl/tcb-offsets.sym has
>>
>> #include <sysdep.h>
>> #include <tls.h>
>> #include <kernel-features.h>
>>
>> RESULT offsetof (struct pthread, result)
>> TID offsetof (struct pthread, tid)
>> CANCELHANDLING offsetof (struct pthread, cancelhandling)
>> CLEANUP_JMP_BUF offsetof (struct pthread, cleanup_jmp_buf)
>> MULTIPLE_THREADS_OFFSET offsetof (tcbhead_t, multiple_threads)
>> SYSINFO_OFFSET offsetof (tcbhead_t, sysinfo)
>> CLEANUP offsetof (struct pthread, cleanup)
>> CLEANUP_PREV offsetof (struct _pthread_cleanup_buffer, __prev)
>> MUTEX_FUTEX offsetof (pthread_mutex_t, __data.__lock)
>> POINTER_GUARD offsetof (tcbhead_t, pointer_guard)
>> #ifndef __ASSUME_PRIVATE_FUTEX
>> PRIVATE_FUTEX offsetof (tcbhead_t, private_futex)
>> #endif
>>
>> It covers more than just tcbhead_t.  A separate header file for tcbhead_t
>> won't help here.
> 
> Yes, it's more involved.
> 
>>>> The circular dependency is just a cosmetic warning from make, right?
>>>
>>> It depends on how unlucky you are.  In one case on a many-core machine
>>> with make -j60, I had to kill glibc build since it never stopped.
> 
> If it fixes an actual build issue, then I think your patch is acceptable, although I consider it quite hackish.
> 
> But please do add a comment explaining the issue before:
> 
> +# ifndef GEN_AS_CONST_HEADERS

Agreed, I think the hack is OK, but needs a multi-line comment
explaining *why* the simple route of header disentanglement
is not easily possible and why this is needed to bootstrap
the automatic header building without a circular dependency.
H.J. Lu Feb. 23, 2018, 7:13 p.m. | #6
On Thu, Feb 22, 2018 at 8:46 AM, Carlos O'Donell <carlos@redhat.com> wrote:
> On 02/22/2018 07:11 AM, Florian Weimer wrote:
>> On 02/21/2018 06:19 PM, H.J. Lu wrote:
>>> On Wed, Feb 21, 2018 at 7:40 AM, H.J. Lu <hjl.tools@gmail.com> wrote:
>>>> On Tue, Feb 20, 2018 at 11:09 PM, Florian Weimer <fweimer@redhat.com> wrote:
>>>>> On 02/08/2018 06:58 PM, H.J. Lu wrote:
>>>>>>
>>>>>>          [BZ #22792]
>>>>>>          * Makerules ($(common-objpfx)%.h): Pass -DGEN_AS_CONST_HEADERS
>>>>>>          to $(CC).
>>>>>>          * sysdeps/unix/sysv/linux/i386/lowlevellock.h: Include
>>>>>>          <tcb-offsets.h> only if GEN_AS_CONST_HEADERS isn't defined.
>>>>>>          * sysdeps/unix/sysv/linux/x86_64/lowlevellock.h: Don't include
>>>>>>          <tcb-offsets.h>.
>>>>>
>>>>>
>>>>> It looks to me that a cleaner fix would be to move the definition of the TCB
>>>>> types to a separate header.
>>>>
>>>> I will take a look.
>>>
>>> sysdeps/i386/nptl/tcb-offsets.sym has
>>>
>>> #include <sysdep.h>
>>> #include <tls.h>
>>> #include <kernel-features.h>
>>>
>>> RESULT offsetof (struct pthread, result)
>>> TID offsetof (struct pthread, tid)
>>> CANCELHANDLING offsetof (struct pthread, cancelhandling)
>>> CLEANUP_JMP_BUF offsetof (struct pthread, cleanup_jmp_buf)
>>> MULTIPLE_THREADS_OFFSET offsetof (tcbhead_t, multiple_threads)
>>> SYSINFO_OFFSET offsetof (tcbhead_t, sysinfo)
>>> CLEANUP offsetof (struct pthread, cleanup)
>>> CLEANUP_PREV offsetof (struct _pthread_cleanup_buffer, __prev)
>>> MUTEX_FUTEX offsetof (pthread_mutex_t, __data.__lock)
>>> POINTER_GUARD offsetof (tcbhead_t, pointer_guard)
>>> #ifndef __ASSUME_PRIVATE_FUTEX
>>> PRIVATE_FUTEX offsetof (tcbhead_t, private_futex)
>>> #endif
>>>
>>> It covers more than just tcbhead_t.  A separate header file for tcbhead_t
>>> won't help here.
>>
>> Yes, it's more involved.
>>
>>>>> The circular dependency is just a cosmetic warning from make, right?
>>>>
>>>> It depends on how unlucky you are.  In one case on a many-core machine
>>>> with make -j60, I had to kill glibc build since it never stopped.
>>
>> If it fixes an actual build issue, then I think your patch is acceptable, although I consider it quite hackish.
>>
>> But please do add a comment explaining the issue before:
>>
>> +# ifndef GEN_AS_CONST_HEADERS
>
> Agreed, I think the hack is OK, but needs a multi-line comment
> explaining *why* the simple route of header disentanglement
> is not easily possible and why this is needed to bootstrap
> the automatic header building without a circular dependency.
>

This is the patch I am checking in.

Thanks.

Patch

diff --git a/Makerules b/Makerules
index ef6abeac6d..10a2e83468 100644
--- a/Makerules
+++ b/Makerules
@@ -276,10 +276,12 @@  ifdef gen-as-const-headers
 # Generating headers for assembly constants.
 # We need this defined early to get into before-compile before
 # it's used in sysd-rules, below.
+# Define GEN_AS_CONST_HEADERS to avoid circular dependency [BZ #22792].
 $(common-objpfx)%.h $(common-objpfx)%.h.d: $(..)scripts/gen-as-const.awk \
 					   %.sym $(common-before-compile)
 	$(AWK) -f $< $(filter %.sym,$^) \
-	| $(CC) -S -o $(@:.h.d=.h)T3 $(CFLAGS) $(CPPFLAGS) -x c - \
+	| $(CC) -S -o $(@:.h.d=.h)T3 $(CFLAGS) $(CPPFLAGS) \
+		-DGEN_AS_CONST_HEADERS -x c - \
 		-MD -MP -MF $(@:.h=.h.d)T -MT '$(@:.h=.h.d) $(@:.h.d=.h)'
 	sed -n 's/^.*@@@name@@@\([^@]*\)@@@value@@@[^0-9Xxa-fA-F-]*\([0-9Xxa-fA-F-][0-9Xxa-fA-F-]*\).*@@@end@@@.*$$/#define \1 \2/p' \
 		$(@:.h.d=.h)T3 > $(@:.h.d=.h)T
diff --git a/sysdeps/unix/sysv/linux/i386/lowlevellock.h b/sysdeps/unix/sysv/linux/i386/lowlevellock.h
index fb59b57934..9f081e8a05 100644
--- a/sysdeps/unix/sysv/linux/i386/lowlevellock.h
+++ b/sysdeps/unix/sysv/linux/i386/lowlevellock.h
@@ -26,7 +26,9 @@ 
 # include <sys/param.h>
 # include <bits/pthreadtypes.h>
 # include <kernel-features.h>
-# include <tcb-offsets.h>
+# ifndef GEN_AS_CONST_HEADERS
+#  include <tcb-offsets.h>
+# endif
 
 # ifndef LOCK_INSTR
 #  ifdef UP
diff --git a/sysdeps/unix/sysv/linux/x86_64/lowlevellock.h b/sysdeps/unix/sysv/linux/x86_64/lowlevellock.h
index a8bcfbe4a3..eedb6fc990 100644
--- a/sysdeps/unix/sysv/linux/x86_64/lowlevellock.h
+++ b/sysdeps/unix/sysv/linux/x86_64/lowlevellock.h
@@ -26,7 +26,6 @@ 
 # include <sys/param.h>
 # include <bits/pthreadtypes.h>
 # include <kernel-features.h>
-# include <tcb-offsets.h>
 
 # ifndef LOCK_INSTR
 #  ifdef UP