* [patch 2.4.11-pre5] atomic_dec_and_lock() for alpha
@ 2001-10-08 15:42 Ivan Kokshaysky
2001-10-08 17:24 ` Richard Henderson
0 siblings, 1 reply; 5+ messages in thread
From: Ivan Kokshaysky @ 2001-10-08 15:42 UTC (permalink / raw)
To: Richard Henderson; +Cc: linux-kernel
Similar to x86 version, but somewhat simpler due to ll/sc.
Ivan.
--- 2.4.11p5/arch/alpha/lib/dec_and_lock.c Thu Jan 1 00:00:00 1970
+++ linux/arch/alpha/lib/dec_and_lock.c Fri Oct 5 17:37:20 2001
@@ -0,0 +1,35 @@
+/*
+ * arch/alpha/lib/dec_and_lock.c
+ *
+ * ll/sc version of atomic_dec_and_lock()
+ */
+
+#include <linux/spinlock.h>
+#include <asm/atomic.h>
+
+int atomic_dec_and_lock(atomic_t *atomic, spinlock_t *lock)
+{
+ int cnt;
+ __asm__ __volatile__(
+ "1: ldl_l %0,%1\n"
+ " subl %0,1,%0\n"
+ " beq %0,2f\n"
+ " stl_c %0,%1\n"
+ " beq %0,3f\n"
+ " mb\n"
+ " mov $31,$0\n"
+ " ret\n"
+ "2:\n"
+ ".subsection 2\n"
+ "3: br 1b\n"
+ ".previous"
+ :"=&r" (cnt), "=m" (atomic->counter)
+ :"m" (atomic->counter) : "$0", "memory");
+
+ /* Slow path */
+ spin_lock(lock);
+ if (atomic_dec_and_test(atomic))
+ return 1;
+ spin_unlock(lock);
+ return 0;
+}
--- 2.4.11p5/arch/alpha/lib/Makefile Wed Jun 20 22:10:27 2001
+++ linux/arch/alpha/lib/Makefile Fri Oct 5 17:37:20 2001
@@ -49,6 +49,10 @@ OBJS = __divqu.o __remqu.o __divlu.o __r
fpreg.o \
callback_srm.o srm_puts.o srm_printk.o
+ifeq ($(CONFIG_SMP),y)
+ OBJS += dec_and_lock.o
+endif
+
lib.a: $(OBJS)
$(AR) rcs lib.a $(OBJS)
--- 2.4.11p5/arch/alpha/kernel/alpha_ksyms.c Fri Sep 14 02:21:32 2001
+++ linux/arch/alpha/kernel/alpha_ksyms.c Fri Oct 5 19:56:39 2001
@@ -215,6 +215,7 @@ EXPORT_SYMBOL(__global_cli);
EXPORT_SYMBOL(__global_sti);
EXPORT_SYMBOL(__global_save_flags);
EXPORT_SYMBOL(__global_restore_flags);
+EXPORT_SYMBOL(atomic_dec_and_lock);
#if DEBUG_SPINLOCK
EXPORT_SYMBOL(spin_unlock);
EXPORT_SYMBOL(debug_spin_lock);
--- 2.4.11p5/arch/alpha/config.in Fri Oct 5 17:27:50 2001
+++ linux/arch/alpha/config.in Fri Oct 5 17:37:20 2001
@@ -217,6 +217,10 @@ then
bool 'Symmetric multi-processing support' CONFIG_SMP
fi
+if [ "$CONFIG_SMP" = "y" ]; then
+ define_bool CONFIG_HAVE_DEC_LOCK y
+fi
+
if [ "$CONFIG_EXPERIMENTAL" = "y" ]; then
bool 'Discontiguous Memory Support' CONFIG_DISCONTIGMEM
if [ "$CONFIG_DISCONTIGMEM" = "y" ]; then
^ permalink raw reply [flat|nested] 5+ messages in thread* Re: [patch 2.4.11-pre5] atomic_dec_and_lock() for alpha
2001-10-08 15:42 [patch 2.4.11-pre5] atomic_dec_and_lock() for alpha Ivan Kokshaysky
@ 2001-10-08 17:24 ` Richard Henderson
2001-10-09 10:30 ` Ivan Kokshaysky
0 siblings, 1 reply; 5+ messages in thread
From: Richard Henderson @ 2001-10-08 17:24 UTC (permalink / raw)
To: Ivan Kokshaysky; +Cc: linux-kernel
On Mon, Oct 08, 2001 at 07:42:57PM +0400, Ivan Kokshaysky wrote:
> + " ret\n"
I am extremely uncomfortable with you returning out of the middle of
an asm statement. What if the compiler decides to allocate a stack
frame for some reason? You'll return without deallocating it.
Please write the whole thing in assembly or avoid the early return.
r~
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [patch 2.4.11-pre5] atomic_dec_and_lock() for alpha
2001-10-08 17:24 ` Richard Henderson
@ 2001-10-09 10:30 ` Ivan Kokshaysky
2001-10-11 18:28 ` Richard Henderson
0 siblings, 1 reply; 5+ messages in thread
From: Ivan Kokshaysky @ 2001-10-09 10:30 UTC (permalink / raw)
To: linux-kernel
On Mon, Oct 08, 2001 at 10:24:12AM -0700, Richard Henderson wrote:
> I am extremely uncomfortable with you returning out of the middle of
> an asm statement. What if the compiler decides to allocate a stack
> frame for some reason? You'll return without deallocating it.
Indeed.
> Please write the whole thing in assembly or avoid the early return.
OK. I prefer the latter - rewriting in assembly won't allow DEBUG_SPINLOCK
stuff in this function. OTOH, moving the return outside an asm statement
adds only one instruction - conditional branch that falls through in the
fast path.
Ivan.
--- 2.4.11p5/arch/alpha/lib/dec_and_lock.c Thu Jan 1 00:00:00 1970
+++ linux/arch/alpha/lib/dec_and_lock.c Tue Oct 9 14:15:01 2001
@@ -0,0 +1,37 @@
+/*
+ * arch/alpha/lib/dec_and_lock.c
+ *
+ * ll/sc version of atomic_dec_and_lock()
+ */
+
+#include <linux/compiler.h>
+#include <linux/spinlock.h>
+#include <asm/atomic.h>
+
+int atomic_dec_and_lock(atomic_t *atomic, spinlock_t *lock)
+{
+ long cnt;
+ __asm__ __volatile__(
+ "1: ldl_l %0,%1\n"
+ " subl %0,1,%0\n"
+ " beq %0,2f\n"
+ " stl_c %0,%1\n"
+ " beq %0,3f\n"
+ " mb\n"
+ "2:\n"
+ ".subsection 2\n"
+ "3: br 1b\n"
+ ".previous"
+ :"=&r" (cnt), "=m" (atomic->counter)
+ :"m" (atomic->counter) : "memory");
+
+ if (likely(cnt))
+ return 0;
+
+ /* Slow path */
+ spin_lock(lock);
+ if (atomic_dec_and_test(atomic))
+ return 1;
+ spin_unlock(lock);
+ return 0;
+}
--- 2.4.11p5/arch/alpha/lib/Makefile Wed Jun 20 22:10:27 2001
+++ linux/arch/alpha/lib/Makefile Fri Oct 5 17:37:20 2001
@@ -49,6 +49,10 @@ OBJS = __divqu.o __remqu.o __divlu.o __r
fpreg.o \
callback_srm.o srm_puts.o srm_printk.o
+ifeq ($(CONFIG_SMP),y)
+ OBJS += dec_and_lock.o
+endif
+
lib.a: $(OBJS)
$(AR) rcs lib.a $(OBJS)
--- 2.4.11p5/arch/alpha/kernel/alpha_ksyms.c Fri Sep 14 02:21:32 2001
+++ linux/arch/alpha/kernel/alpha_ksyms.c Fri Oct 5 19:56:39 2001
@@ -215,6 +215,7 @@ EXPORT_SYMBOL(__global_cli);
EXPORT_SYMBOL(__global_sti);
EXPORT_SYMBOL(__global_save_flags);
EXPORT_SYMBOL(__global_restore_flags);
+EXPORT_SYMBOL(atomic_dec_and_lock);
#if DEBUG_SPINLOCK
EXPORT_SYMBOL(spin_unlock);
EXPORT_SYMBOL(debug_spin_lock);
--- 2.4.11p5/arch/alpha/config.in Fri Oct 5 17:27:50 2001
+++ linux/arch/alpha/config.in Fri Oct 5 17:37:20 2001
@@ -217,6 +217,10 @@ then
bool 'Symmetric multi-processing support' CONFIG_SMP
fi
+if [ "$CONFIG_SMP" = "y" ]; then
+ define_bool CONFIG_HAVE_DEC_LOCK y
+fi
+
if [ "$CONFIG_EXPERIMENTAL" = "y" ]; then
bool 'Discontiguous Memory Support' CONFIG_DISCONTIGMEM
if [ "$CONFIG_DISCONTIGMEM" = "y" ]; then
^ permalink raw reply [flat|nested] 5+ messages in thread* Re: [patch 2.4.11-pre5] atomic_dec_and_lock() for alpha
2001-10-09 10:30 ` Ivan Kokshaysky
@ 2001-10-11 18:28 ` Richard Henderson
2001-10-12 12:35 ` Ivan Kokshaysky
0 siblings, 1 reply; 5+ messages in thread
From: Richard Henderson @ 2001-10-11 18:28 UTC (permalink / raw)
To: Ivan Kokshaysky; +Cc: linux-kernel
On Tue, Oct 09, 2001 at 02:30:13PM +0400, Ivan Kokshaysky wrote:
> OK. I prefer the latter - rewriting in assembly won't allow DEBUG_SPINLOCK
> stuff in this function. OTOH, moving the return outside an asm statement
> adds only one instruction - conditional branch that falls through in the
> fast path.
Hmm. What about a mixture:
asm (".text \n\
.global atomic_dec_and_lock \n\
.ent atomic_dec_and_lock \n\
atomic_dec_and_lock: \n\
.prologue 0 \n\
1: ldl_l $1, 0($16) \n\
subl $1, 1, $1 \n\
beq 2f \n\
stl_c $1, 0($16) \n\
beq $1, 3f \n\
mb \n\
ret \n\
.align 4 \n\
3: br 1b \n\
2: lda $27, atomic_dec_and_lock_1");
/* FALLTHRU */
static int
atomic_dec_and_lock_1(atomic_t *atomic, spinlock_t *lock)
{
/* Slow path */
spin_lock(lock);
if (atomic_dec_and_test(atomic))
return 1;
spin_unlock(lock);
return 0;
}
r~
^ permalink raw reply [flat|nested] 5+ messages in thread* Re: [patch 2.4.11-pre5] atomic_dec_and_lock() for alpha
2001-10-11 18:28 ` Richard Henderson
@ 2001-10-12 12:35 ` Ivan Kokshaysky
0 siblings, 0 replies; 5+ messages in thread
From: Ivan Kokshaysky @ 2001-10-12 12:35 UTC (permalink / raw)
To: linux-kernel
On Thu, Oct 11, 2001 at 11:28:10AM -0700, Richard Henderson wrote:
> Hmm. What about a mixture:
...
> 2: lda $27, atomic_dec_and_lock_1");
>
> /* FALLTHRU */
>
> static int
> atomic_dec_and_lock_1(atomic_t *atomic, spinlock_t *lock)
Oh cool.
I've made a patch of the above (with some minor changes), but
are you certain that these two will be linked in proper order
under any circumstances? Or "br atomic_dec_and_lock_1" is
needed?
Ivan.
--- 2.4.13p1/arch/alpha/lib/dec_and_lock.c Thu Jan 1 00:00:00 1970
+++ linux/arch/alpha/lib/dec_and_lock.c Fri Oct 12 14:48:57 2001
@@ -0,0 +1,41 @@
+/*
+ * arch/alpha/lib/dec_and_lock.c
+ *
+ * ll/sc version of atomic_dec_and_lock() and nice example
+ * of mixing C and assembly.
+ *
+ */
+
+#include <linux/spinlock.h>
+#include <asm/atomic.h>
+
+ asm (".text \n\
+ .global atomic_dec_and_lock \n\
+ .ent atomic_dec_and_lock \n\
+ .align 4 \n\
+atomic_dec_and_lock: \n\
+ .prologue 0 \n\
+1: ldl_l $1, 0($16) \n\
+ subl $1, 1, $1 \n\
+ beq $1, 2f \n\
+ stl_c $1, 0($16) \n\
+ beq $1, 3f \n\
+ mb \n\
+ clr $0 \n\
+ ret \n\
+3: br 1b \n\
+2: lda $27, atomic_dec_and_lock_1 \n\
+ .end atomic_dec_and_lock");
+
+ /* FALLTHRU */
+
+static int __attribute__((unused))
+atomic_dec_and_lock_1(atomic_t *atomic, spinlock_t *lock)
+{
+ /* Slow path */
+ spin_lock(lock);
+ if (atomic_dec_and_test(atomic))
+ return 1;
+ spin_unlock(lock);
+ return 0;
+}
--- 2.4.13p1/arch/alpha/lib/Makefile Wed Jun 20 22:10:27 2001
+++ linux/arch/alpha/lib/Makefile Fri Oct 5 17:37:20 2001
@@ -49,6 +49,10 @@ OBJS = __divqu.o __remqu.o __divlu.o __r
fpreg.o \
callback_srm.o srm_puts.o srm_printk.o
+ifeq ($(CONFIG_SMP),y)
+ OBJS += dec_and_lock.o
+endif
+
lib.a: $(OBJS)
$(AR) rcs lib.a $(OBJS)
--- 2.4.13p1/arch/alpha/kernel/alpha_ksyms.c Fri Sep 14 02:21:32 2001
+++ linux/arch/alpha/kernel/alpha_ksyms.c Fri Oct 5 19:56:39 2001
@@ -215,6 +215,7 @@ EXPORT_SYMBOL(__global_cli);
EXPORT_SYMBOL(__global_sti);
EXPORT_SYMBOL(__global_save_flags);
EXPORT_SYMBOL(__global_restore_flags);
+EXPORT_SYMBOL(atomic_dec_and_lock);
#if DEBUG_SPINLOCK
EXPORT_SYMBOL(spin_unlock);
EXPORT_SYMBOL(debug_spin_lock);
--- 2.4.13p1/arch/alpha/config.in Fri Oct 5 17:27:50 2001
+++ linux/arch/alpha/config.in Fri Oct 5 17:37:20 2001
@@ -217,6 +217,10 @@ then
bool 'Symmetric multi-processing support' CONFIG_SMP
fi
+if [ "$CONFIG_SMP" = "y" ]; then
+ define_bool CONFIG_HAVE_DEC_LOCK y
+fi
+
if [ "$CONFIG_EXPERIMENTAL" = "y" ]; then
bool 'Discontiguous Memory Support' CONFIG_DISCONTIGMEM
if [ "$CONFIG_DISCONTIGMEM" = "y" ]; then
^ permalink raw reply [flat|nested] 5+ messages in thread
end of thread, other threads:[~2001-10-12 12:36 UTC | newest]
Thread overview: 5+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2001-10-08 15:42 [patch 2.4.11-pre5] atomic_dec_and_lock() for alpha Ivan Kokshaysky
2001-10-08 17:24 ` Richard Henderson
2001-10-09 10:30 ` Ivan Kokshaysky
2001-10-11 18:28 ` Richard Henderson
2001-10-12 12:35 ` Ivan Kokshaysky
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox