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SubjectRe: Re: RFC: patch to allow lock-free traversal of lists with insertion ^M
Date
>In message <Pine.LNX.4.33.0110120919130.31677-100000@penguin.transmeta.com> you
> write:
>> And hey, if you want to, feel free to create the regular
>>
>> #define read_barrier() rmb()
>> #define write_barrier() wmb()
>> #define memory_barrier() mb()
>
>I agree... read_barrier_depends() then?
>
>Rusty.
>--
>Premature optmztion is rt of all evl. --DK

OK, here is an RFC patch with the read_barrier_depends(). (I know that
the indentation is messed up, will fix when I add the read_barrier()
and friends).

Thoughts? Especially from people familiar with MIPS and PA-RISC?

Thanx, Paul

diff -urN -X /home/mckenney/dontdiff linux-2.4.10/include/asm-alpha/system.h linux-2.4.10.read_barrier_depends/include/asm-alpha/system.h
--- linux-2.4.10/include/asm-alpha/system.h Sun Aug 12 10:38:47 2001
+++ linux-2.4.10.read_barrier_depends/include/asm-alpha/system.h Sat Oct 13 08:40:34 2001
@@ -148,16 +148,21 @@
#define rmb() \
__asm__ __volatile__("mb": : :"memory")

+#define read_barrier_depends() \
+__asm__ __volatile__("mb": : :"memory")
+
#define wmb() \
__asm__ __volatile__("wmb": : :"memory")

#ifdef CONFIG_SMP
#define smp_mb() mb()
#define smp_rmb() rmb()
+#define smp_read_barrier_depends() read_barrier_depends()
#define smp_wmb() wmb()
#else
#define smp_mb() barrier()
#define smp_rmb() barrier()
+#define smp_read_barrier_depends() barrier()
#define smp_wmb() barrier()
#endif

diff -urN -X /home/mckenney/dontdiff linux-2.4.10/include/asm-arm/system.h linux-2.4.10.read_barrier_depends/include/asm-arm/system.h
--- linux-2.4.10/include/asm-arm/system.h Mon Nov 27 17:07:59 2000
+++ linux-2.4.10.read_barrier_depends/include/asm-arm/system.h Sat Oct 13 08:40:40 2001
@@ -38,6 +38,7 @@

#define mb() __asm__ __volatile__ ("" : : : "memory")
#define rmb() mb()
+#define read_barrier_depends() do { } while(0)
#define wmb() mb()
#define nop() __asm__ __volatile__("mov\tr0,r0\t@ nop\n\t");

@@ -67,12 +68,14 @@

#define smp_mb() mb()
#define smp_rmb() rmb()
+#define smp_read_barrier_depends() read_barrier_depends()
#define smp_wmb() wmb()

#else

#define smp_mb() barrier()
#define smp_rmb() barrier()
+#define smp_read_barrier_depends() do { } while(0)
#define smp_wmb() barrier()

#define cli() __cli()
diff -urN -X /home/mckenney/dontdiff linux-2.4.10/include/asm-cris/system.h linux-2.4.10.read_barrier_depends/include/asm-cris/system.h
--- linux-2.4.10/include/asm-cris/system.h Tue May 1 16:05:00 2001
+++ linux-2.4.10.read_barrier_depends/include/asm-cris/system.h Sat Oct 13 08:40:48 2001
@@ -143,15 +143,18 @@

#define mb() __asm__ __volatile__ ("" : : : "memory")
#define rmb() mb()
+#define read_barrier_depends() do { } while(0)
#define wmb() mb()

#ifdef CONFIG_SMP
#define smp_mb() mb()
#define smp_rmb() rmb()
+#define smp_read_barrier_depends() read_barrier_depends()
#define smp_wmb() wmb()
#else
#define smp_mb() barrier()
#define smp_rmb() barrier()
+#define smp_read_barrier_depends() do { } while(0)
#define smp_wmb() barrier()
#endif

diff -urN -X /home/mckenney/dontdiff linux-2.4.10/include/asm-i386/system.h linux-2.4.10.read_barrier_depends/include/asm-i386/system.h
--- linux-2.4.10/include/asm-i386/system.h Sun Sep 23 10:31:01 2001
+++ linux-2.4.10.read_barrier_depends/include/asm-i386/system.h Sat Oct 13 08:40:54 2001
@@ -284,15 +284,18 @@
*/
#define mb() __asm__ __volatile__ ("lock; addl $0,0(%%esp)": : :"memory")
#define rmb() mb()
+#define read_barrier_depends() do { } while(0)
#define wmb() __asm__ __volatile__ ("": : :"memory")

#ifdef CONFIG_SMP
#define smp_mb() mb()
#define smp_rmb() rmb()
+#define smp_read_barrier_depends() read_barrier_depends()
#define smp_wmb() wmb()
#else
#define smp_mb() barrier()
#define smp_rmb() barrier()
+#define smp_read_barrier_depends() do { } while(0)
#define smp_wmb() barrier()
#endif

diff -urN -X /home/mckenney/dontdiff linux-2.4.10/include/asm-ia64/system.h linux-2.4.10.read_barrier_depends/include/asm-ia64/system.h
--- linux-2.4.10/include/asm-ia64/system.h Tue Jul 31 10:30:09 2001
+++ linux-2.4.10.read_barrier_depends/include/asm-ia64/system.h Sat Oct 13 08:55:13 2001
@@ -85,6 +85,9 @@
* stores and that all following stores will be
* visible only after all previous stores.
* rmb(): Like wmb(), but for reads.
+ * read_barrier_depends(): Like rmb(), but only for pairs
+ * of loads where the second load depends on the
+ * value loaded by the first.
* mb(): wmb()/rmb() combo, i.e., all previous memory
* accesses are visible before all subsequent
* accesses and vice versa. This is also known as
@@ -98,15 +101,18 @@
*/
#define mb() __asm__ __volatile__ ("mf" ::: "memory")
#define rmb() mb()
+#define read_barrier_depends() do { } while(0)
#define wmb() mb()

#ifdef CONFIG_SMP
# define smp_mb() mb()
# define smp_rmb() rmb()
+# define smp_read_barrier_depends() read_barrier_depends()
# define smp_wmb() wmb()
#else
# define smp_mb() barrier()
# define smp_rmb() barrier()
+# define smp_read_barrier_depends() do { } while(0)
# define smp_wmb() barrier()
#endif

diff -urN -X /home/mckenney/dontdiff linux-2.4.10/include/asm-m68k/system.h linux-2.4.10.read_barrier_depends/include/asm-m68k/system.h
--- linux-2.4.10/include/asm-m68k/system.h Mon Jun 11 19:15:27 2001
+++ linux-2.4.10.read_barrier_depends/include/asm-m68k/system.h Sat Oct 13 08:41:08 2001
@@ -80,12 +80,14 @@
#define nop() do { asm volatile ("nop"); barrier(); } while (0)
#define mb() barrier()
#define rmb() barrier()
+#define read_barrier_depends() do { } while(0)
#define wmb() barrier()
#define set_mb(var, value) do { xchg(&var, value); } while (0)
#define set_wmb(var, value) do { var = value; wmb(); } while (0)

#define smp_mb() barrier()
#define smp_rmb() barrier()
+#define smp_read_barrier_depends() do { } while(0)
#define smp_wmb() barrier()


diff -urN -X /home/mckenney/dontdiff linux-2.4.10/include/asm-mips/system.h linux-2.4.10.read_barrier_depends/include/asm-mips/system.h
--- linux-2.4.10/include/asm-mips/system.h Sun Sep 9 10:43:01 2001
+++ linux-2.4.10.read_barrier_depends/include/asm-mips/system.h Sat Oct 13 08:41:14 2001
@@ -150,6 +150,7 @@

#include <asm/wbflush.h>
#define rmb() do { } while(0)
+#define read_barrier_depends() do { } while(0)
#define wmb() wbflush()
#define mb() wbflush()

@@ -166,6 +167,7 @@
: /* no input */ \
: "memory")
#define rmb() mb()
+#define read_barrier_depends() do { } while(0)
#define wmb() mb()

#endif /* CONFIG_CPU_HAS_WB */
@@ -173,10 +175,12 @@
#ifdef CONFIG_SMP
#define smp_mb() mb()
#define smp_rmb() rmb()
+#define smp_read_barrier_depends() read_barrier_depends()
#define smp_wmb() wmb()
#else
#define smp_mb() barrier()
#define smp_rmb() barrier()
+#define smp_read_barrier_depends() do { } while(0)
#define smp_wmb() barrier()
#endif

diff -urN -X /home/mckenney/dontdiff linux-2.4.10/include/asm-mips64/system.h linux-2.4.10.read_barrier_depends/include/asm-mips64/system.h
--- linux-2.4.10/include/asm-mips64/system.h Wed Jul 4 11:50:39 2001
+++ linux-2.4.10.read_barrier_depends/include/asm-mips64/system.h Sat Oct 13 08:41:22 2001
@@ -147,15 +147,18 @@
: /* no input */ \
: "memory")
#define rmb() mb()
+#define read_barrier_depends() do { } while(0)
#define wmb() mb()

#ifdef CONFIG_SMP
#define smp_mb() mb()
#define smp_rmb() rmb()
+#define smp_read_barrier_depends() read_barrier_depends()
#define smp_wmb() wmb()
#else
#define smp_mb() barrier()
#define smp_rmb() barrier()
+#define smp_read_barrier_depends() do { } while(0)
#define smp_wmb() barrier()
#endif

diff -urN -X /home/mckenney/dontdiff linux-2.4.10/include/asm-parisc/system.h linux-2.4.10.read_barrier_depends/include/asm-parisc/system.h
--- linux-2.4.10/include/asm-parisc/system.h Wed Dec 6 11:46:39 2000
+++ linux-2.4.10.read_barrier_depends/include/asm-parisc/system.h Sat Oct 13 08:41:28 2001
@@ -50,6 +50,7 @@
#ifdef CONFIG_SMP
#define smp_mb() mb()
#define smp_rmb() rmb()
+#define smp_read_barrier_depends() do { } while(0)
#define smp_wmb() wmb()
#else
/* This is simply the barrier() macro from linux/kernel.h but when serial.c
@@ -58,6 +59,7 @@
*/
#define smp_mb() __asm__ __volatile__("":::"memory");
#define smp_rmb() __asm__ __volatile__("":::"memory");
+#define smp_read_barrier_depends() do { } while(0)
#define smp_wmb() __asm__ __volatile__("":::"memory");
#endif

@@ -122,6 +124,7 @@

#define mb() __asm__ __volatile__ ("sync" : : :"memory")
#define wmb() mb()
+#define read_barrier_depends() do { } while(0)

extern unsigned long __xchg(unsigned long, unsigned long *, int);

diff -urN -X /home/mckenney/dontdiff linux-2.4.10/include/asm-ppc/system.h linux-2.4.10.read_barrier_depends/include/asm-ppc/system.h
--- linux-2.4.10/include/asm-ppc/system.h Tue Aug 28 06:58:33 2001
+++ linux-2.4.10.read_barrier_depends/include/asm-ppc/system.h Sat Oct 13 08:41:56 2001
@@ -24,6 +24,8 @@
*
* mb() prevents loads and stores being reordered across this point.
* rmb() prevents loads being reordered across this point.
+ * read_barrier_depends() prevents data-dependant loads being reordered
+ * across this point (nop on PPC).
* wmb() prevents stores being reordered across this point.
*
* We can use the eieio instruction for wmb, but since it doesn't
@@ -32,6 +34,7 @@
*/
#define mb() __asm__ __volatile__ ("sync" : : : "memory")
#define rmb() __asm__ __volatile__ ("sync" : : : "memory")
+#define read_barrier_depends() do { } while(0)
#define wmb() __asm__ __volatile__ ("eieio" : : : "memory")

#define set_mb(var, value) do { var = value; mb(); } while (0)
@@ -40,10 +43,12 @@
#ifdef CONFIG_SMP
#define smp_mb() mb()
#define smp_rmb() rmb()
+#define smp_read_barrier_depends() read_barrier_depends()
#define smp_wmb() wmb()
#else
#define smp_mb() __asm__ __volatile__("": : :"memory")
#define smp_rmb() __asm__ __volatile__("": : :"memory")
+#define smp_read_barrier_depends() do { } while(0)
#define smp_wmb() __asm__ __volatile__("": : :"memory")
#endif /* CONFIG_SMP */

diff -urN -X /home/mckenney/dontdiff linux-2.4.10/include/asm-s390/system.h linux-2.4.10.read_barrier_depends/include/asm-s390/system.h
--- linux-2.4.10/include/asm-s390/system.h Wed Jul 25 14:12:02 2001
+++ linux-2.4.10.read_barrier_depends/include/asm-s390/system.h Sat Oct 13 08:42:08 2001
@@ -117,9 +117,11 @@
# define SYNC_OTHER_CORES(x) eieio()
#define mb() eieio()
#define rmb() eieio()
+#define read_barrier_depends() do { } while(0)
#define wmb() eieio()
#define smp_mb() mb()
#define smp_rmb() rmb()
+#define smp_read_barrier_depends() read_barrier_depends()
#define smp_wmb() wmb()
#define smp_mb__before_clear_bit() smp_mb()
#define smp_mb__after_clear_bit() smp_mb()
diff -urN -X /home/mckenney/dontdiff linux-2.4.10/include/asm-s390x/system.h linux-2.4.10.read_barrier_depends/include/asm-s390x/system.h
--- linux-2.4.10/include/asm-s390x/system.h Wed Jul 25 14:12:03 2001
+++ linux-2.4.10.read_barrier_depends/include/asm-s390x/system.h Sat Oct 13 08:42:14 2001
@@ -130,9 +130,11 @@
# define SYNC_OTHER_CORES(x) eieio()
#define mb() eieio()
#define rmb() eieio()
+#define read_barrier_depends() do { } while(0)
#define wmb() eieio()
#define smp_mb() mb()
#define smp_rmb() rmb()
+#define smp_read_barrier_depends() read_barrier_depends()
#define smp_wmb() wmb()
#define smp_mb__before_clear_bit() smp_mb()
#define smp_mb__after_clear_bit() smp_mb()
diff -urN -X /home/mckenney/dontdiff linux-2.4.10/include/asm-sh/system.h linux-2.4.10.read_barrier_depends/include/asm-sh/system.h
--- linux-2.4.10/include/asm-sh/system.h Sat Sep 8 12:29:09 2001
+++ linux-2.4.10.read_barrier_depends/include/asm-sh/system.h Sat Oct 13 08:43:04 2001
@@ -88,15 +88,18 @@

#define mb() __asm__ __volatile__ ("": : :"memory")
#define rmb() mb()
+#define read_barrier_depends() do { } while(0)
#define wmb() __asm__ __volatile__ ("": : :"memory")

#ifdef CONFIG_SMP
#define smp_mb() mb()
#define smp_rmb() rmb()
+#define smp_read_barrier_depends() read_barrier_depends()
#define smp_wmb() wmb()
#else
#define smp_mb() barrier()
#define smp_rmb() barrier()
+#define smp_read_barrier_depends() do { } while(0)
#define smp_wmb() barrier()
#endif

diff -urN -X /home/mckenney/dontdiff linux-2.4.10/include/asm-sparc/system.h linux-2.4.10.read_barrier_depends/include/asm-sparc/system.h
--- linux-2.4.10/include/asm-sparc/system.h Tue Oct 3 09:24:41 2000
+++ linux-2.4.10.read_barrier_depends/include/asm-sparc/system.h Sat Oct 13 08:43:09 2001
@@ -277,11 +277,13 @@
/* XXX Change this if we ever use a PSO mode kernel. */
#define mb() __asm__ __volatile__ ("" : : : "memory")
#define rmb() mb()
+#define read_barrier_depends() do { } while(0)
#define wmb() mb()
#define set_mb(__var, __value) do { __var = __value; mb(); } while(0)
#define set_wmb(__var, __value) set_mb(__var, __value)
#define smp_mb() __asm__ __volatile__("":::"memory");
#define smp_rmb() __asm__ __volatile__("":::"memory");
+#define smp_read_barrier_depends() do { } while(0)
#define smp_wmb() __asm__ __volatile__("":::"memory");

#define nop() __asm__ __volatile__ ("nop");
diff -urN -X /home/mckenney/dontdiff linux-2.4.10/include/asm-sparc64/system.h linux-2.4.10.read_barrier_depends/include/asm-sparc64/system.h
--- linux-2.4.10/include/asm-sparc64/system.h Fri Sep 7 11:01:20 2001
+++ linux-2.4.10.read_barrier_depends/include/asm-sparc64/system.h Sat Oct 13 08:43:14 2001
@@ -99,6 +99,7 @@
#define mb() \
membar("#LoadLoad | #LoadStore | #StoreStore | #StoreLoad");
#define rmb() membar("#LoadLoad")
+#define read_barrier_depends() do { } while(0)
#define wmb() membar("#StoreStore")
#define set_mb(__var, __value) \
do { __var = __value; membar("#StoreLoad | #StoreStore"); } while(0)
@@ -108,10 +109,12 @@
#ifdef CONFIG_SMP
#define smp_mb() mb()
#define smp_rmb() rmb()
+#define smp_read_barrier_depends() read_barrier_depends()
#define smp_wmb() wmb()
#else
#define smp_mb() __asm__ __volatile__("":::"memory");
#define smp_rmb() __asm__ __volatile__("":::"memory");
+#define smp_read_barrier_depends() do { } while(0)
#define smp_wmb() __asm__ __volatile__("":::"memory");
#endif

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