On 2014-12-04 16:38:45 +0200, Heikki Linnakangas wrote:
> On 11/23/2014 08:37 PM, Vladimir Koković wrote:
> >PostgreSQL check-world regress failed with current GIT HEAD on my Kubuntu
> >14.10.
> >
> >uname -a
> >Linux vlD-kuci 3.16.0-24-generic #32-Ubuntu SMP Tue Oct 28 13:13:18 UTC
> >2014 i686 athlon i686 GNU/Linux
> >
> >gdb -d /home/src/postgresql-devel/postgresql-git/postgresql/src -c core
> >...
> >Loaded symbols for
> >/home/src/postgresql-devel/dev-build/src/test/regress/regress.so
> >(gdb) bt
> >#0 0xb76ecc7c in __kernel_vsyscall ()
> >#1 0xb7075577 in __GI_raise (sig=sig@entry=6) at
> >../nptl/sysdeps/unix/sysv/linux/raise.c:56
> >#2 0xb7076cf3 in __GI_abort () at abort.c:89
> >#3 0x084c326a in ?? ()
> >#4 0x0a56c3b8 in ?? ()
> >#5 0xb76d232f in pg_atomic_init_u64 (ptr=0xbfa16fd4, val=0) at
> >/home/src/postgresql-devel/postgresql-git/postgresql/src/include/port/atomics.h:445
> >#6 0xb76d50e4 in test_atomic_uint64 () at
> >/home/src/postgresql-devel/postgresql-git/postgresql/src/test/regress/regress.c:1022
> >#7 0xb76d5756 in test_atomic_ops (fcinfo=0xa57c76c) at
> >/home/src/postgresql-devel/postgresql-git/postgresql/src/test/regress/regress.c:1114
> >#8 0x0825bfee in ?? ()
> >...
>
> Andres, have you had a chance to look at this?
Nope, missed it somehow.
> On 32-bit x86, arch-x86.h leaves PG_HAVE_ATOMIC_U64_SUPPORT undefined. But
> generic-gcc.h, which is included later, then defines it.
That's fine. The only reason arch-x86.h implements anything itself is
that that allows older compilers than relying on intrinsics. But
implementing 64bit atomics is too annoying by hand and isn't currently
required.
> pg_atomic_init_u64 does AssertPointerAlignment(ptr, 8) on the variable, but
> there is no guarantee that it is 8-bytes aligned on x86.
Hrmpf. Annoying. Gcc for a while claimed that was guaranteed, but, if I
understood the tickets correctly, gave up on that.
Unfortunately we have to rely (IIRC) on that for (quite old) x86s and
some other architectures. It doesn't seem to be a problem on any native
64bit platform, because 64bit variables are 8byte aligned natively
there.
I think it can relatively easily be fixed by something like the
attached. Don't have a pure 32bit environment to test though - the
problem isn't reproducable in a 32bit chroot...
Vladimir, if you apply that patch, do things work for you?
Greetings,
Andres Freund
--
Andres Freund http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services
diff --git a/src/include/port/atomics/arch-x86.h b/src/include/port/atomics/arch-x86.h
index fb5623d..168a49c 100644
--- a/src/include/port/atomics/arch-x86.h
+++ b/src/include/port/atomics/arch-x86.h
@@ -73,6 +73,7 @@ typedef struct pg_atomic_uint32
#define PG_HAVE_ATOMIC_U64_SUPPORT
typedef struct pg_atomic_uint64
{
+ /* alignment guaranteed due to being on a 64bit platform */
volatile uint64 value;
} pg_atomic_uint64;
#endif
diff --git a/src/include/port/atomics/generic-acc.h b/src/include/port/atomics/generic-acc.h
index e16e282..c5639aa 100644
--- a/src/include/port/atomics/generic-acc.h
+++ b/src/include/port/atomics/generic-acc.h
@@ -40,6 +40,12 @@ typedef struct pg_atomic_uint32
#define PG_HAVE_ATOMIC_U64_SUPPORT
typedef struct pg_atomic_uint64
{
+ /*
+ * Alignment is guaranteed to be 64bit. Search for "Well-behaved
+ * application restrictions" => "Data alignment and data sharing" on HP's
+ * website. Unfortunately the URL doesn't seem to stable enough to
+ * include.
+ */
volatile uint64 value;
} pg_atomic_uint64;
diff --git a/src/include/port/atomics/generic-gcc.h b/src/include/port/atomics/generic-gcc.h
index f19ad34..fea1cb5 100644
--- a/src/include/port/atomics/generic-gcc.h
+++ b/src/include/port/atomics/generic-gcc.h
@@ -98,7 +98,7 @@ typedef struct pg_atomic_uint32
typedef struct pg_atomic_uint64
{
- volatile uint64 value;
+ volatile uint64 value __attribute__((aligned(8)));
} pg_atomic_uint64;
#endif /* defined(HAVE_GCC__ATOMIC_INT64_CAS) || defined(HAVE_GCC__SYNC_INT64_CAS) */
diff --git a/src/include/port/atomics/generic-msvc.h b/src/include/port/atomics/generic-msvc.h
index 1d763ab..d259d6f 100644
--- a/src/include/port/atomics/generic-msvc.h
+++ b/src/include/port/atomics/generic-msvc.h
@@ -41,7 +41,7 @@ typedef struct pg_atomic_uint32
} pg_atomic_uint32;
#define PG_HAVE_ATOMIC_U64_SUPPORT
-typedef struct pg_atomic_uint64
+typedef struct __declspec(align(8)) pg_atomic_uint64
{
volatile uint64 value;
} pg_atomic_uint64;
diff --git a/src/include/port/atomics/generic-sunpro.h b/src/include/port/atomics/generic-sunpro.h
index b756fb9..7a3028e 100644
--- a/src/include/port/atomics/generic-sunpro.h
+++ b/src/include/port/atomics/generic-sunpro.h
@@ -55,7 +55,13 @@ typedef struct pg_atomic_uint32
#define PG_HAVE_ATOMIC_U64_SUPPORT
typedef struct pg_atomic_uint64
{
- volatile uint64 value;
+ /*
+ * Syntax to enforce variable alignment should be supported by versions
+ * supporting atomic.h, but it's hard to find accurate documentation. If
+ * it proves to be a problem, we'll have to add more version checks for 64
+ * bit support.
+ */
+ volatile uint64 value __attribute__((__aligned__(8)));
} pg_atomic_uint64;
#endif /* HAVE_ATOMIC_H */
diff --git a/src/include/port/atomics/generic-xlc.h b/src/include/port/atomics/generic-xlc.h
index 92bba6f..7a4c12a 100644
--- a/src/include/port/atomics/generic-xlc.h
+++ b/src/include/port/atomics/generic-xlc.h
@@ -32,7 +32,7 @@ typedef struct pg_atomic_uint32
#define PG_HAVE_ATOMIC_U64_SUPPORT
typedef struct pg_atomic_uint64
{
- volatile uint64 value;
+ volatile uint64 value __attribute__((__aligned__(8)));
} pg_atomic_uint64;
#endif /* __64BIT__ */
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