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SubjectRe: [patch 2.4.11-pre5] atomic_dec_and_lock() for alpha
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
-
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