[PATCH] ppc64: Replace custom locking code with a spinlock
The hvlpevent_queue (formally ItLpQueue) has a member called xInUseWord
which is used for serialising access to the queue. Because it's a word
(ie. 32 bit) there's a custom 32-bit version of test_and_set_bit() or
thereabouts in ItLpQueue.c.
The xInUseWord is not shared with they hypervisor, so we can replace it
with a spinlock and remove the custom code.
There is also another locking mechanism (ItLpQueueInProcess). This is
redundant because it's only manipulated while the lock's held. Remove it.
Signed-off-by: Michael Ellerman <michael@ellerman.id.au>
Acked-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Paul Mackerras <paulus@samba.org>
diff --git a/arch/ppc64/kernel/ItLpQueue.c b/arch/ppc64/kernel/ItLpQueue.c
index a4f32cb..4231861 100644
--- a/arch/ppc64/kernel/ItLpQueue.c
+++ b/arch/ppc64/kernel/ItLpQueue.c
@@ -42,35 +42,8 @@
"Virtual I/O"
};
-static __inline__ int set_inUse(void)
-{
- int t;
- u32 * inUseP = &hvlpevent_queue.xInUseWord;
-
- __asm__ __volatile__("\n\
-1: lwarx %0,0,%2 \n\
- cmpwi 0,%0,0 \n\
- li %0,0 \n\
- bne- 2f \n\
- addi %0,%0,1 \n\
- stwcx. %0,0,%2 \n\
- bne- 1b \n\
-2: eieio"
- : "=&r" (t), "=m" (hvlpevent_queue.xInUseWord)
- : "r" (inUseP), "m" (hvlpevent_queue.xInUseWord)
- : "cc");
-
- return t;
-}
-
-static __inline__ void clear_inUse(void)
-{
- hvlpevent_queue.xInUseWord = 0;
-}
-
/* Array of LpEvent handler functions */
extern LpEventHandler lpEventHandler[HvLpEvent_Type_NumTypes];
-unsigned long ItLpQueueInProcess = 0;
static struct HvLpEvent * get_next_hvlpevent(void)
{
@@ -144,14 +117,9 @@
struct HvLpEvent * event;
/* If we have recursed, just return */
- if ( !set_inUse() )
+ if (!spin_trylock(&hvlpevent_queue.lock))
return;
- if (ItLpQueueInProcess == 0)
- ItLpQueueInProcess = 1;
- else
- BUG();
-
for (;;) {
event = get_next_hvlpevent();
if (event) {
@@ -187,9 +155,7 @@
break;
}
- ItLpQueueInProcess = 0;
- mb();
- clear_inUse();
+ spin_unlock(&hvlpevent_queue.lock);
}
static int set_spread_lpevents(char *str)
