From: Arjan van de Ven <arjan@infradead.org>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Eric Dumazet <eric.dumazet@gmail.com>,
Martin Schwidefsky <schwidefsky@de.ibm.com>,
Thomas Gleixner <tglx@linutronix.de>,
John Stultz <johnstul@us.ibm.com>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Peter Zijlstra <a.p.zijlstra@chello.nl>,
Ingo Molnar <mingo@elte.hu>
Subject: Re: Linux 2.6.32-rc1
Date: Wed, 30 Sep 2009 17:07:54 +0200 [thread overview]
Message-ID: <20090930170754.0886ff2e@infradead.org> (raw)
In-Reply-To: <alpine.LFD.2.01.0909291429570.6996@localhost.localdomain>
On Tue, 29 Sep 2009 14:56:28 -0700 (PDT)
Linus Torvalds <torvalds@linux-foundation.org> wrote:
>
>
> On Tue, 29 Sep 2009, Arjan van de Ven wrote:
> >
> > can't we use alternatives() for this, to patch cmpxchg64 in ?
> > I mean.. it'll be commonly supported nowadays.. the fallback to it
> > not being supported could be a bit slower by now...
>
> Yes, we could. It would limit us to some fixed address format,
> probably
>
> cmpxchg8b (%esi)
>
> or something. Use something like this as a starting point, perhaps?
>
> NOTE! Totally untested! And you'd actually need to implement the
> "cmpxchg8b_emu" function that takes it's arguments in %eax:%edx,
> %ebx:%ecx and %esi and doesn't trash any other registers..
so I debugged this guy (had a few bugs ;-)
patch, including a new cmpxchg8b_emu below:
>From 5a76986c5dd272ea16a9b8abb7349ff3d6791c2b Mon Sep 17 00:00:00 2001
From: Arjan van de Ven <arjan@linux.intel.com>
Date: Wed, 30 Sep 2009 17:04:35 +0200
Subject: [PATCH] x86: Provide an alternative() based cmpxchg64()
Based on Linus' patch, this patch provides cmpxchg64() using
the alternative() infrastructure.
Note: the fallback is NOT smp safe, just like the current fallback
is not SMP safe.
Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
---
arch/x86/include/asm/cmpxchg_32.h | 29 ++++++++++--------
arch/x86/kernel/i386_ksyms_32.c | 3 ++
arch/x86/lib/Makefile | 2 +-
arch/x86/lib/cmpxchg8b_emu.S | 61 +++++++++++++++++++++++++++++++++++++
4 files changed, 81 insertions(+), 14 deletions(-)
create mode 100644 arch/x86/lib/cmpxchg8b_emu.S
diff --git a/arch/x86/include/asm/cmpxchg_32.h b/arch/x86/include/asm/cmpxchg_32.h
index 82ceb78..3b21afa 100644
--- a/arch/x86/include/asm/cmpxchg_32.h
+++ b/arch/x86/include/asm/cmpxchg_32.h
@@ -312,19 +312,22 @@ static inline unsigned long cmpxchg_386(volatile void *ptr, unsigned long old,
extern unsigned long long cmpxchg_486_u64(volatile void *, u64, u64);
-#define cmpxchg64(ptr, o, n) \
-({ \
- __typeof__(*(ptr)) __ret; \
- if (likely(boot_cpu_data.x86 > 4)) \
- __ret = (__typeof__(*(ptr)))__cmpxchg64((ptr), \
- (unsigned long long)(o), \
- (unsigned long long)(n)); \
- else \
- __ret = (__typeof__(*(ptr)))cmpxchg_486_u64((ptr), \
- (unsigned long long)(o), \
- (unsigned long long)(n)); \
- __ret; \
-})
+#define cmpxchg64(ptr, o, n) \
+({ \
+ __typeof__(*(ptr)) __ret; \
+ __typeof__(*(ptr)) __old = (o); \
+ __typeof__(*(ptr)) __new = (n); \
+ alternative_io("call cmpxchg8b_emu", \
+ "lock; cmpxchg8b (%%esi)" , \
+ X86_FEATURE_CX8, \
+ "=A" (__ret), \
+ "S" ((ptr)), "0" (__old), \
+ "b" ((unsigned int)__new), \
+ "c" ((unsigned int)(__new>>32))); \
+ __ret; })
+
+
+
#define cmpxchg64_local(ptr, o, n) \
({ \
__typeof__(*(ptr)) __ret; \
diff --git a/arch/x86/kernel/i386_ksyms_32.c b/arch/x86/kernel/i386_ksyms_32.c
index 43cec6b..f17930e 100644
--- a/arch/x86/kernel/i386_ksyms_32.c
+++ b/arch/x86/kernel/i386_ksyms_32.c
@@ -10,6 +10,9 @@
EXPORT_SYMBOL(mcount);
#endif
+extern void cmpxchg8b_emu(void); /* dummy proto */
+EXPORT_SYMBOL(cmpxchg8b_emu);
+
/* Networking helper routines. */
EXPORT_SYMBOL(csum_partial_copy_generic);
diff --git a/arch/x86/lib/Makefile b/arch/x86/lib/Makefile
index 9e60920..3e549b8 100644
--- a/arch/x86/lib/Makefile
+++ b/arch/x86/lib/Makefile
@@ -15,7 +15,7 @@ ifeq ($(CONFIG_X86_32),y)
obj-y += atomic64_32.o
lib-y += checksum_32.o
lib-y += strstr_32.o
- lib-y += semaphore_32.o string_32.o
+ lib-y += semaphore_32.o string_32.o cmpxchg8b_emu.o
lib-$(CONFIG_X86_USE_3DNOW) += mmx_32.o
else
diff --git a/arch/x86/lib/cmpxchg8b_emu.S b/arch/x86/lib/cmpxchg8b_emu.S
new file mode 100644
index 0000000..b8af4c7
--- /dev/null
+++ b/arch/x86/lib/cmpxchg8b_emu.S
@@ -0,0 +1,61 @@
+/*
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; version 2
+ * of the License.
+ *
+ */
+
+#include <linux/linkage.h>
+#include <asm/alternative-asm.h>
+#include <asm/frame.h>
+#include <asm/dwarf2.h>
+
+
+.text
+
+/*
+ * Inputs:
+ * %esi : memory location to compare
+ * %eax : low 32 bits of old value
+ * %edx : high 32 bits of old value
+ * %ebx : low 32 bits of new value
+ * %ecx : high 32 bits of new value
+ */
+ENTRY(cmpxchg8b_emu)
+ CFI_STARTPROC
+
+ push %edi
+ push %ebx
+ push %ecx
+ /* disable interrupts */
+ pushf
+ pop %edi
+ cli
+
+ cmpl %edx, 4(%esi)
+ jne 1f
+ cmpl %eax, (%esi)
+ jne 1f
+
+ xchg (%esi), %ebx
+ xchg 4(%esi), %ecx
+ mov %ebx, %eax
+ mov %ecx, %edx
+
+2:
+ /* restore interrupts */
+ push %edi
+ popf
+
+ pop %ecx
+ pop %ebx
+ pop %edi
+ ret
+1:
+ mov (%esi), %eax
+ mov 4(%esi), %edx
+ jmp 2b
+ CFI_ENDPROC
+ENDPROC(cmpxchg8b_emu)
+
--
1.6.2.5
next prev parent reply other threads:[~2009-09-30 15:07 UTC|newest]
Thread overview: 80+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-09-27 22:34 Linux 2.6.32-rc1 Linus Torvalds
2009-09-27 23:44 ` Stephen Rothwell
2009-09-27 23:48 ` Diego Calleja
2009-09-27 23:52 ` Linus Torvalds
2009-09-28 0:17 ` Stephen Rothwell
2009-09-28 7:07 ` Eric Dumazet
2009-09-28 15:39 ` Linus Torvalds
2009-09-28 17:15 ` Martin Schwidefsky
2009-09-28 18:41 ` Eric Dumazet
2009-09-28 20:56 ` Martin Schwidefsky
2009-09-29 20:42 ` Eric Dumazet
2009-09-29 21:17 ` Linus Torvalds
2009-09-29 21:22 ` Arjan van de Ven
2009-09-29 21:56 ` Linus Torvalds
2009-09-30 15:07 ` Arjan van de Ven [this message]
2009-09-30 15:27 ` Eric Dumazet
2009-09-30 15:31 ` Arjan van de Ven
2009-10-01 0:42 ` Yuhong Bao
2009-09-30 15:57 ` Eric Dumazet
2009-09-30 16:13 ` Arjan van de Ven
2009-09-30 16:14 ` Linus Torvalds
2009-09-30 18:53 ` Ingo Molnar
2009-09-30 22:03 ` [GIT PULL] scheduler fixes Ingo Molnar
2009-10-01 0:42 ` Linus Torvalds
2009-10-01 0:57 ` Linus Torvalds
2009-10-01 5:30 ` Eric Dumazet
2009-10-01 6:11 ` Ingo Molnar
2009-10-01 6:18 ` Eric Dumazet
2009-10-01 6:42 ` Ingo Molnar
2009-10-01 6:59 ` Eric Dumazet
2009-10-01 7:28 ` Sam Ravnborg
2009-10-01 6:49 ` [tip:x86/urgent] x86: Don't generate cmpxchg8b_emu if CONFIG_X86_CMPXCHG64=y tip-bot for Eric Dumazet
2009-10-01 6:40 ` [tip:x86/urgent] x86: Optimize cmpxchg64() at build-time some more tip-bot for Linus Torvalds
2009-10-02 16:40 ` [GIT PULL] scheduler fixes Yuhong Bao
2009-10-01 6:05 ` Ingo Molnar
2009-09-30 16:14 ` Linux 2.6.32-rc1 Cyrill Gorcunov
2009-09-30 16:55 ` Stefan Richter
2009-09-30 17:08 ` Linus Torvalds
2009-09-30 17:40 ` Stefan Richter
2009-09-30 19:32 ` Ingo Molnar
2009-09-30 19:35 ` Ingo Molnar
2009-09-30 20:16 ` Eric Dumazet
2009-09-30 20:20 ` Linus Torvalds
2009-09-30 20:22 ` Ingo Molnar
2009-09-30 20:38 ` Ingo Molnar
2009-10-01 7:18 ` Arjan van de Ven
2009-09-30 19:37 ` [tip:sched/urgent] x86: Provide an alternative() based cmpxchg64() tip-bot for Arjan van de Ven
2009-09-30 19:37 ` [tip:sched/urgent] sched_clock: Fix atomicity/continuity bug by using cmpxchg64() tip-bot for Arjan van de Ven
2009-09-30 19:39 ` Ingo Molnar
2009-09-30 19:39 ` tip-bot for Eric Dumazet
2009-09-30 20:19 ` Linux 2.6.32-rc1 Linus Torvalds
2009-09-30 20:24 ` Eric Dumazet
2009-09-30 20:41 ` Linus Torvalds
2009-09-30 20:49 ` Ingo Molnar
2009-09-30 20:53 ` Eric Dumazet
2009-09-30 21:00 ` Ingo Molnar
2009-09-30 20:54 ` Linus Torvalds
2009-09-30 21:53 ` David Miller
2009-10-01 12:48 ` Christoph Hellwig
2009-10-01 16:08 ` Valdis.Kletnieks
2009-10-05 14:39 ` Peter Zijlstra
2009-09-30 20:40 ` [tip:sched/urgent] x86: Provide an alternative() based cmpxchg64() tip-bot for Arjan van de Ven
2009-09-30 20:58 ` Ingo Molnar
2009-09-30 20:40 ` [tip:sched/urgent] sched_clock: Fix atomicity/continuity bug by using cmpxchg64() tip-bot for Eric Dumazet
2009-09-30 20:55 ` [tip:sched/urgent] x86: Provide an alternative() based cmpxchg64() tip-bot for Arjan van de Ven
2009-09-30 20:55 ` [tip:sched/urgent] sched_clock: Fix atomicity/continuity bug by using cmpxchg64() tip-bot for Eric Dumazet
2009-09-30 21:00 ` [tip:sched/urgent] x86: Provide an alternative() based cmpxchg64() tip-bot for Arjan van de Ven
2009-09-30 21:01 ` [tip:sched/urgent] sched_clock: Fix atomicity/continuity bug by using cmpxchg64() tip-bot for Eric Dumazet
2009-10-05 16:00 ` [PATCH] x86: Generate cmpxchg build failures Peter Zijlstra
2009-10-05 18:51 ` Maciej Żenczykowski
2009-10-05 19:16 ` Linus Torvalds
2009-10-05 19:33 ` Peter Zijlstra
2009-10-05 20:54 ` Linus Torvalds
2009-10-09 14:23 ` [tip:x86/asm] " tip-bot for Peter Zijlstra
2009-09-28 14:34 ` Linux 2.6.32-rc1 compile error Wolfgang Erig
2009-09-28 15:10 ` Jaswinder Singh Rajput
2009-09-28 15:32 ` Wolfgang Erig
2009-09-28 16:25 ` [PATCH] isdn: fix netjet/isdnhdlc build errors Randy Dunlap
2009-09-28 19:47 ` David Miller
2009-09-28 22:10 Linux 2.6.32-rc1 devzero
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20090930170754.0886ff2e@infradead.org \
--to=arjan@infradead.org \
--cc=a.p.zijlstra@chello.nl \
--cc=eric.dumazet@gmail.com \
--cc=johnstul@us.ibm.com \
--cc=linux-kernel@vger.kernel.org \
--cc=mingo@elte.hu \
--cc=schwidefsky@de.ibm.com \
--cc=tglx@linutronix.de \
--cc=torvalds@linux-foundation.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).