[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>

[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>
Michael Ellerman · Paul Mackerras
1 parent ffe1b7e14e
Showing 2 changed files with 3 additions and 37 deletions Side-by-side Diff
arch/ppc64/kernel/ItLpQueue.c
include/asm-ppc64/iSeries/ItLpQueue.h
@@ -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)
@@ -69,7 +69,7 @@
 	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;
...	...	@@ -42,35 +42,8 @@
42	42	"Virtual I/O"
43	43	};
44	44
45		-static __inline__ int set_inUse(void)
46		-{
47		- int t;
48		- u32 * inUseP = &hvlpevent_queue.xInUseWord;
49		-
50		- __asm__ __volatile__("\n\
51		-1: lwarx %0,0,%2 \n\
52		- cmpwi 0,%0,0 \n\
53		- li %0,0 \n\
54		- bne- 2f \n\
55		- addi %0,%0,1 \n\
56		- stwcx. %0,0,%2 \n\
57		- bne- 1b \n\
58		-2: eieio"
59		- : "=&r" (t), "=m" (hvlpevent_queue.xInUseWord)
60		- : "r" (inUseP), "m" (hvlpevent_queue.xInUseWord)
61		- : "cc");
62		-
63		- return t;
64		-}
65		-
66		-static __inline__ void clear_inUse(void)
67		-{
68		- hvlpevent_queue.xInUseWord = 0;
69		-}
70		-
71	45	/* Array of LpEvent handler functions */
72	46	extern LpEventHandler lpEventHandler[HvLpEvent_Type_NumTypes];
73		-unsigned long ItLpQueueInProcess = 0;
74	47
75	48	static struct HvLpEvent * get_next_hvlpevent(void)
76	49	{
77	50
...	...	@@ -144,14 +117,9 @@
144	117	struct HvLpEvent * event;
145	118
146	119	/* If we have recursed, just return */
147		- if ( !set_inUse() )
	120	+ if (!spin_trylock(&hvlpevent_queue.lock))
148	121	return;
149	122
150		- if (ItLpQueueInProcess == 0)
151		- ItLpQueueInProcess = 1;
152		- else
153		- BUG();
154		-
155	123	for (;;) {
156	124	event = get_next_hvlpevent();
157	125	if (event) {
...	...	@@ -187,9 +155,7 @@
187	155	break;
188	156	}
189	157
190		- ItLpQueueInProcess = 0;
191		- mb();
192		- clear_inUse();
	158	+ spin_unlock(&hvlpevent_queue.lock);
193	159	}
194	160
195	161	static int set_spread_lpevents(char *str)
...	...	@@ -69,7 +69,7 @@
69	69	char *xSlicEventStackPtr; // 0x20
70	70	u8 xIndex; // 0x28 unique sequential index.
71	71	u8 xSlicRsvd[3]; // 0x29-2b
72		- u32 xInUseWord; // 0x2C
	72	+ spinlock_t lock;
73	73	};
74	74
75	75	extern struct hvlpevent_queue hvlpevent_queue;