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[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>
This commit is contained in:
Michael Ellerman 2005-06-30 15:17:02 +10:00 committed by Paul Mackerras
parent ffe1b7e14e
commit 719d1cd867
2 changed files with 3 additions and 37 deletions
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38
arch/ppc64/kernel/ItLpQueue.c
View File

@ -42,35 +42,8 @@ static char *event_types[HvLpEvent_Type_NumTypes] = {
"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 @@ void process_hvlpevents(struct pt_regs *regs)
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 @@ void process_hvlpevents(struct pt_regs *regs)
break;
}
ItLpQueueInProcess = 0;
mb();
clear_inUse();
spin_unlock(&hvlpevent_queue.lock);
}
static int set_spread_lpevents(char *str)

2
include/asm-ppc64/iSeries/ItLpQueue.h
View File

@ -69,7 +69,7 @@ struct hvlpevent_queue {
char *xSlicEventStackPtr; // 0x20
u8 xIndex; // 0x28 unique sequential index.
u8 xSlicRsvd[3]; // 0x29-2b
u32 xInUseWord; // 0x2C
spinlock_t lock;
};
extern struct hvlpevent_queue hvlpevent_queue;