DB_THREAD support in Berkeley DB/glibc
Daniel Jacobowitz
drow at false.org
Wed Dec 29 09:05:39 EST 1999
I'm fixing this up right now... From what I could see, the tsl_t is a
char but this accesses it as a long; dare I just assume that struct
alignment will do the right thing? My current code conditionally sets
tsl_t to an unsigned long on powerpc, via sysdeps.
And no, UNSET is not sufficient, from what I can tell - at least on
SMP.
I used sync at both ends, by analogy to the mutexes for linuxthreads;
is this wrong/unnecessary?
Does this implementation look right? I'm away from my powerpc at the
moment, so I haven't even been able to verify that it compiles.
On Tue, Dec 28, 1999 at 02:02:03PM -0500, David Edelsohn wrote:
>
> +/*
> + * PowerPC spinlock, adapted from the Alpha and m68k ones by dhd at debian.org
> + *
> + * For gcc/powerpc, 0 is clear, 1 is set (but *tsl will always be 0 since it's a char)
> + */
> +#define TSL_SET(tsl) ({ \
> + register tsl_t *__l = (tsl); \
> + register tsl_t __r1; \
> + __asm__ volatile(" \n\
> + 10: lwarx %0,0,%1 \n\
> + cmpwi %0,0 \n\
> + bne+ 20f \n\
> + stwcx. %2,0,%1 \n\
> + bne- 10b \n\
> + 20: " \
> + : "=&r" (__r1) \
> + : "r" (__l), "r" (-1) : "cr0", "memory"); \
> + !__r1; \
> +})
> +
> +#define TSL_UNSET(tsl) (*(tsl) = 0)
> +#define TSL_INIT(tsl) TSL_UNSET(tsl)
>
> The TSL_SET macro is basically correct for PowerPC uniprocessor,
> but it is not MP safe. For cases where this needs to be safe across a
> multiprocessor complex, it should be preceded by a "sync" instruction and
> ended with an "isync" instruction, or something similar depending on the
> semantics one uses for accessing the word.
>
> It is not clear to me why the TSL_UNSET macro is sufficient.
Dan
/--------------------------------\ /--------------------------------\
| Daniel Jacobowitz |__| SCS Class of 2002 |
| Debian GNU/Linux Developer __ Carnegie Mellon University |
| dan at debian.org | | dmj+ at andrew.cmu.edu |
\--------------------------------/ \--------------------------------/
-------------- next part --------------
diff -uNr db2.orig/config.h db2/config.h
--- db2.orig/config.h Tue Jun 9 11:02:06 1998
+++ db2/config.h Tue Dec 28 15:52:12 1999
@@ -66,6 +66,12 @@
/* Define if you want to use sparc/gcc assembly spinlocks. */
/* #undef HAVE_ASSEM_SPARC_GCC */
+/* Define if you want to use alpha/gcc assembly spinlocks. */
+/* #undef HAVE_ASSEM_ALPHA_GCC */
+
+/* Define if you want to use powerpc/gcc assembly spinlocks. */
+/* #undef HAVE_ASSEM_POWERPC_GCC */
+
/* Define if you want to use uts4/cc assembly spinlocks. */
/* #undef HAVE_ASSEM_UTS4_CC */
diff -uNr db2.orig/db_int.h db2/db_int.h
--- db2.orig/db_int.h Mon Aug 31 11:57:53 1998
+++ db2/db_int.h Tue Dec 28 15:55:05 1999
@@ -153,8 +153,11 @@
/*******************************************************
* Mutex support.
*******************************************************/
+#ifdef SPINLOCK_TYPE
+typedef SPINLOCK_TYPE tsl_t;
+#else
typedef unsigned char tsl_t;
-
+#endif
/*
@@ -165,7 +168,10 @@
* region. This ensures the alignment is as returned by mmap(2), which should
* be sufficient. All other mutex users must ensure proper alignment locally.
*/
+
+#ifndef MUTEX_ALIGNMENT
#define MUTEX_ALIGNMENT 1
+#endif
/*
* The offset of a mutex in memory.
diff -uNr db2.orig/mutex/alpha.gcc db2/mutex/alpha.gcc
--- db2.orig/mutex/alpha.gcc Wed Aug 27 15:32:54 1997
+++ db2/mutex/alpha.gcc Tue Dec 28 15:52:12 1999
@@ -31,22 +31,23 @@
register tsl_t *__l = (tsl); \
register tsl_t __r1, __r2; \
__asm__ volatile(" \n\
- 10: ldq_l %0,(%2) \n\
+ 10: ldl_l %0,%3 \n\
blbs %0,30f \n\
or %0,1,%1 \n\
- stq_c %1,(%2) \n\
+ stl_c %1,%2 \n\
beq %1,20f \n\
mb \n\
br 30f \n\
20: br 10b \n\
30: " \
- : "=&r" (__r1), "=&r" (__r2) \
- : "r" (__l)); \
+ : "=&r" (__r1), "=&r" (__r2), "=m"(*__l) \
+ : "2" (*__l) \
+ : "memory"); \
!__r1; \
})
#define TSL_UNSET(tsl) ({ \
register tsl_t *__l = (tsl); \
- __asm__ volatile("mb; stq $31,(%0);" : : "r" (__l)); \
+ __asm__ volatile("mb; stl $31,%0;" : "=m" (*__l) : : "memory"); \
})
#define TSL_INIT(tsl) TSL_UNSET(tsl)
diff -uNr db2.orig/mutex/mutex.c db2/mutex/mutex.c
--- db2.orig/mutex/mutex.c Tue Jun 9 11:04:35 1998
+++ db2/mutex/mutex.c Tue Dec 28 15:52:12 1999
@@ -86,6 +86,14 @@
#include "sparc.gcc"
#endif
+#ifdef HAVE_ASSEM_ALPHA_GCC
+#include "alpha.gcc"
+#endif
+
+#ifdef HAVE_ASSEM_POWERPC_GCC
+#include "powerpc.gcc"
+#endif
+
#ifdef HAVE_ASSEM_UTS4_CC
#define TSL_INIT(x)
#define TSL_SET(x) (!uts_lock(x, 1))
diff -uNr db2.orig/mutex/powerpc.gcc db2/mutex/powerpc.gcc
--- db2.orig/mutex/powerpc.gcc Wed Dec 31 19:00:00 1969
+++ db2/mutex/powerpc.gcc Tue Dec 28 16:57:31 1999
@@ -0,0 +1,31 @@
+/*
+ * PowerPC spinlock, adapted from the Alpha and m68k ones by dhd at debian.org
+ * and dan at debian.org.
+ *
+ * For gcc/powerpc, 0 is clear, 1 is set.
+ */
+#define TSL_SET(tsl) ({ \
+ register tsl_t *__l = (tsl); \
+ register tsl_t __r1; \
+ __asm__ volatile(" \n\
+ sync \n\
+ 10: lwarx %0,0,%1 \n\
+ cmpwi %0,0 \n\
+ bne+ 20f \n\
+ stwcx. %2,0,%1 \n\
+ bne- 10b \n\
+ sync \n\
+ 20: " \
+ : "=&r" (__r1) \
+ : "r" (__l), "r" (1) : "cr0", "memory"); \
+ !__r1; \
+})
+
+#define TSL_UNSET(tsl) ({ \
+ register tsl_t *__l = (tsl); \
+ __asm__ __volatile__(" \n\
+ sync \n\
+ stw %1, %0" : "=&r" (__l) : "r" (0)); \
+ })
+
+#define TSL_INIT(tsl) TSL_UNSET(tsl)
diff -uNr sysdeps/powerpc.orig/Makefile sysdeps/powerpc/Makefile
--- sysdeps/powerpc.orig/Makefile Tue Dec 28 15:50:56 1999
+++ sysdeps/powerpc/Makefile Tue Dec 28 15:53:01 1999
@@ -25,6 +25,10 @@
CFLAGS-gmon-start.o = -G0
endif
+ifeq ($(subdir),db2)
+CPPFLAGS += -DHAVE_SPINLOCKS=1 -DHAVE_ASSEM_POWERPC_GCC=1 -DSPINLOCK_TYPE='unsigned long' -DMUTEX_ALIGNMENT=4
+endif
+
ifeq ($(subdir),string)
CFLAGS-memcmp.c += -Wno-uninitialized
endif
diff -uNr sysdeps/alpha.orig/Makefile sysdeps/alpha/Makefile
--- sysdeps/alpha.orig/Makefile Tue Dec 28 15:50:56 1999
+++ sysdeps/alpha/Makefile Tue Dec 28 15:52:12 1999
@@ -34,6 +34,10 @@
CFLAGS-rtld.c = -mbuild-constants
endif
+ifeq ($(subdir),db2)
+CPPFLAGS += -DHAVE_SPINLOCKS=1 -DHAVE_ASSEM_ALPHA_GCC=1 -DMUTEX_ALIGNMENT=4
+endif
+
divrem := divl divq reml remq
# For now, build everything with full IEEE math support.
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