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Commit 719d1cd8 authored by Michael Ellerman's avatar Michael Ellerman Committed by Paul Mackerras
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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: default avatarMichael Ellerman <michael@ellerman.id.au>
Acked-by: default avatarStephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: default avatarPaul Mackerras <paulus@samba.org>
parent ffe1b7e1

arch/ppc64/kernel/ItLpQueue.c

+2 −36
Original line number Diff line number Diff line
@@ -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)

include/asm-ppc64/iSeries/ItLpQueue.h

+1 −1
Original line number Diff line number Diff line
@@ -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;