Re: [PATCH v4 2/2] arcmsr: simplify of updating doneq_index and postq_index

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On Fri, 2014-09-12 at 16:05 +0200, Tomas Henzl wrote:
> On 09/12/2014 10:22 AM, Ching Huang wrote:
> > From: Ching Huang <ching2048@xxxxxxxxxxxx>
> >
> > This patch is to modify previous patch 16/17 and it is relative to
> > http://git.infradead.org/users/hch/scsi-queue.git/tree/arcmsr-for-3.18:/drivers/scsi/arcmsr
> >
> > change in v4:
> > 1. clean up of duplicate variable declaration in switch.
> > 2. simplify of updating doneq_index and postq_index
> > 3. fix spin_lock area in arcmsr_hbaD_polling_ccbdone
> 
> The intention of the doneq_lock is to protect the pmu->doneq_index and the associated buffer,
> right? Why is the spinlock not used on other places accessing the doneq_index
> like arcmsr_done4abort_postqueue or arcmsr_hbaD_postqueue_isr ?
In fact, in original code arcmsr_hbaD_postqueue_isr has spinlock with a larger area.
As to arcmsr_done4abort_postqueue, it should be protected as below.

@@ -1182,35 +1178,25 @@ static void arcmsr_done4abort_postqueue(
 		break;
 	case ACB_ADAPTER_TYPE_D: {
 		struct MessageUnit_D  *pmu = acb->pmuD;
-		uint32_t ccb_cdb_phy, outbound_write_pointer;
-		uint32_t doneq_index, index_stripped, addressLow, residual;
-		bool error;
-		struct CommandControlBlock *pCCB;
+		uint32_t outbound_write_pointer;
+		uint32_t doneq_index, index_stripped, addressLow, residual, toggle;
+		unsigned long flags;
 
-		outbound_write_pointer = pmu->done_qbuffer[0].addressLow + 1;
-		doneq_index = pmu->doneq_index;
 		residual = atomic_read(&acb->ccboutstandingcount);
 		for (i = 0; i < residual; i++) {
-			while ((doneq_index & 0xFFF) !=
+			spin_lock_irqsave(&acb->doneq_lock, flags);
+			outbound_write_pointer =
+				pmu->done_qbuffer[0].addressLow + 1;
+			doneq_index = pmu->doneq_index;
+			if ((doneq_index & 0xFFF) !=
 				(outbound_write_pointer & 0xFFF)) {
-				if (doneq_index & 0x4000) {
-					index_stripped = doneq_index & 0xFFF;
-					index_stripped += 1;
-					index_stripped %=
-						ARCMSR_MAX_ARC1214_DONEQUEUE;
-					pmu->doneq_index = index_stripped ?
-						(index_stripped | 0x4000) :
-						(index_stripped + 1);
-				} else {
-					index_stripped = doneq_index;
-					index_stripped += 1;
-					index_stripped %=
-						ARCMSR_MAX_ARC1214_DONEQUEUE;
-					pmu->doneq_index = index_stripped ?
-						index_stripped :
-						((index_stripped | 0x4000) + 1);
-				}
+				toggle = doneq_index & 0x4000;
+				index_stripped = (doneq_index & 0xFFF) + 1;
+				index_stripped %= ARCMSR_MAX_ARC1214_DONEQUEUE;
+				pmu->doneq_index = index_stripped ? (index_stripped | toggle) :
+					((toggle ^ 0x4000) + 1);
 				doneq_index = pmu->doneq_index;
+				spin_unlock_irqrestore(&acb->doneq_lock, flags);
 				addressLow = pmu->done_qbuffer[doneq_index &
 					0xFFF].addressLow;
 				ccb_cdb_phy = (addressLow & 0xFFFFFFF0);
@@ -1224,11 +1210,10 @@ static void arcmsr_done4abort_postqueue(
 				arcmsr_drain_donequeue(acb, pCCB, error);
 				writel(doneq_index,
 					pmu->outboundlist_read_pointer);
+			} else {
+				spin_unlock_irqrestore(&acb->doneq_lock, flags);
+				mdelay(10);
 			}
-			mdelay(10);
-			outbound_write_pointer =
-				pmu->done_qbuffer[0].addressLow + 1;
-			doneq_index = pmu->doneq_index;
 		}
 		pmu->postq_index = 0;
 		pmu->doneq_index = 0x40FF;


> And in arcmsr_hbaD_polling_ccbdone the code looks so:
> 
>                 spin_unlock_irqrestore(&acb->doneq_lock, flags);
>                 doneq_index = pmu->doneq_index;
> 		flag_ccb = pmu->done_qbuffer[doneq_index & 0xFFF].addressLow;
> you unlock^ and after that is the value read and used
> Seems to me that I probably don't understand what the spinlock should protect.
> Could you explain ?
You are right. above code should change to 

                  doneq_index = pmu->doneq_index;
                  spin_unlock_irqrestore(&acb->doneq_lock, flags);
                  flag_ccb = pmu->done_qbuffer[doneq_index & 0xFFF].addressLow;
> Thanks,
> Tomas
> 
>  
> 
> >
> > Signed-off-by: Ching Huang <ching2048@xxxxxxxxxxxx>
> > ---
> >
> > diff -uprN a/drivers/scsi/arcmsr/arcmsr_hba.c b/drivers/scsi/arcmsr/arcmsr_hba.c
> > --- a/drivers/scsi/arcmsr/arcmsr_hba.c	2014-09-12 12:43:16.956653000 +0800
> > +++ b/drivers/scsi/arcmsr/arcmsr_hba.c	2014-09-12 15:00:23.516069000 +0800
> > @@ -1121,7 +1121,7 @@ static void arcmsr_drain_donequeue(struc
> >  static void arcmsr_done4abort_postqueue(struct AdapterControlBlock *acb)
> >  {
> >  	int i = 0;
> > -	uint32_t flag_ccb;
> > +	uint32_t flag_ccb, ccb_cdb_phy;
> >  	struct ARCMSR_CDB *pARCMSR_CDB;
> >  	bool error;
> >  	struct CommandControlBlock *pCCB;
> > @@ -1165,10 +1165,6 @@ static void arcmsr_done4abort_postqueue(
> >  		break;
> >  	case ACB_ADAPTER_TYPE_C: {
> >  		struct MessageUnit_C __iomem *reg = acb->pmuC;
> > -		struct  ARCMSR_CDB *pARCMSR_CDB;
> > -		uint32_t flag_ccb, ccb_cdb_phy;
> > -		bool error;
> > -		struct CommandControlBlock *pCCB;
> >  		while ((readl(&reg->host_int_status) & ARCMSR_HBCMU_OUTBOUND_POSTQUEUE_ISR) && (i++ < ARCMSR_MAX_OUTSTANDING_CMD)) {
> >  			/*need to do*/
> >  			flag_ccb = readl(&reg->outbound_queueport_low);
> > @@ -1182,10 +1178,8 @@ static void arcmsr_done4abort_postqueue(
> >  		break;
> >  	case ACB_ADAPTER_TYPE_D: {
> >  		struct MessageUnit_D  *pmu = acb->pmuD;
> > -		uint32_t ccb_cdb_phy, outbound_write_pointer;
> > -		uint32_t doneq_index, index_stripped, addressLow, residual;
> > -		bool error;
> > -		struct CommandControlBlock *pCCB;
> > +		uint32_t outbound_write_pointer;
> > +		uint32_t doneq_index, index_stripped, addressLow, residual, toggle;
> >  
> >  		outbound_write_pointer = pmu->done_qbuffer[0].addressLow + 1;
> >  		doneq_index = pmu->doneq_index;
> > @@ -1193,23 +1187,11 @@ static void arcmsr_done4abort_postqueue(
> >  		for (i = 0; i < residual; i++) {
> >  			while ((doneq_index & 0xFFF) !=
> >  				(outbound_write_pointer & 0xFFF)) {
> > -				if (doneq_index & 0x4000) {
> > -					index_stripped = doneq_index & 0xFFF;
> > -					index_stripped += 1;
> > -					index_stripped %=
> > -						ARCMSR_MAX_ARC1214_DONEQUEUE;
> > -					pmu->doneq_index = index_stripped ?
> > -						(index_stripped | 0x4000) :
> > -						(index_stripped + 1);
> > -				} else {
> > -					index_stripped = doneq_index;
> > -					index_stripped += 1;
> > -					index_stripped %=
> > -						ARCMSR_MAX_ARC1214_DONEQUEUE;
> > -					pmu->doneq_index = index_stripped ?
> > -						index_stripped :
> > -						((index_stripped | 0x4000) + 1);
> > -				}
> > +				toggle = doneq_index & 0x4000;
> > +				index_stripped = (doneq_index & 0xFFF) + 1;
> > +				index_stripped %= ARCMSR_MAX_ARC1214_DONEQUEUE;
> > +				pmu->doneq_index = index_stripped ? (index_stripped | toggle) :
> > +					((toggle ^ 0x4000) + 1);
> >  				doneq_index = pmu->doneq_index;
> >  				addressLow = pmu->done_qbuffer[doneq_index &
> >  					0xFFF].addressLow;
> > @@ -1461,7 +1443,7 @@ static void arcmsr_post_ccb(struct Adapt
> >  	case ACB_ADAPTER_TYPE_D: {
> >  		struct MessageUnit_D  *pmu = acb->pmuD;
> >  		u16 index_stripped;
> > -		u16 postq_index;
> > +		u16 postq_index, toggle;
> >  		unsigned long flags;
> >  		struct InBound_SRB *pinbound_srb;
> >  
> > @@ -1472,19 +1454,11 @@ static void arcmsr_post_ccb(struct Adapt
> >  		pinbound_srb->addressLow = dma_addr_lo32(cdb_phyaddr);
> >  		pinbound_srb->length = ccb->arc_cdb_size >> 2;
> >  		arcmsr_cdb->msgContext = dma_addr_lo32(cdb_phyaddr);
> > -		if (postq_index & 0x4000) {
> > -			index_stripped = postq_index & 0xFF;
> > -			index_stripped += 1;
> > -			index_stripped %= ARCMSR_MAX_ARC1214_POSTQUEUE;
> > -			pmu->postq_index = index_stripped ?
> > -				(index_stripped | 0x4000) : index_stripped;
> > -		} else {
> > -			index_stripped = postq_index;
> > -			index_stripped += 1;
> > -			index_stripped %= ARCMSR_MAX_ARC1214_POSTQUEUE;
> > -			pmu->postq_index = index_stripped ? index_stripped :
> > -				(index_stripped | 0x4000);
> > -		}
> > +		toggle = postq_index & 0x4000;
> > +		index_stripped = postq_index + 1;
> > +		index_stripped &= (ARCMSR_MAX_ARC1214_POSTQUEUE - 1);
> > +		pmu->postq_index = index_stripped ? (index_stripped | toggle) :
> > +			(toggle ^ 0x4000);
> >  		writel(postq_index, pmu->inboundlist_write_pointer);
> >  		spin_unlock_irqrestore(&acb->postq_lock, flags);
> >  		break;
> > @@ -1999,7 +1973,7 @@ static void arcmsr_hbaC_postqueue_isr(st
> >  
> >  static void arcmsr_hbaD_postqueue_isr(struct AdapterControlBlock *acb)
> >  {
> > -	u32 outbound_write_pointer, doneq_index, index_stripped;
> > +	u32 outbound_write_pointer, doneq_index, index_stripped, toggle;
> >  	uint32_t addressLow, ccb_cdb_phy;
> >  	int error;
> >  	struct MessageUnit_D  *pmu;
> > @@ -2013,21 +1987,11 @@ static void arcmsr_hbaD_postqueue_isr(st
> >  	doneq_index = pmu->doneq_index;
> >  	if ((doneq_index & 0xFFF) != (outbound_write_pointer & 0xFFF)) {
> >  		do {
> > -			if (doneq_index & 0x4000) {
> > -				index_stripped = doneq_index & 0xFFF;
> > -				index_stripped += 1;
> > -				index_stripped %= ARCMSR_MAX_ARC1214_DONEQUEUE;
> > -				pmu->doneq_index = index_stripped
> > -					? (index_stripped | 0x4000) :
> > -					(index_stripped + 1);
> > -			} else {
> > -				index_stripped = doneq_index;
> > -				index_stripped += 1;
> > -				index_stripped %= ARCMSR_MAX_ARC1214_DONEQUEUE;
> > -				pmu->doneq_index = index_stripped
> > -					? index_stripped :
> > -					((index_stripped | 0x4000) + 1);
> > -			}
> > +			toggle = doneq_index & 0x4000;
> > +			index_stripped = (doneq_index & 0xFFF) + 1;
> > +			index_stripped %= ARCMSR_MAX_ARC1214_DONEQUEUE;
> > +			pmu->doneq_index = index_stripped ? (index_stripped | toggle) :
> > +				((toggle ^ 0x4000) + 1);
> >  			doneq_index = pmu->doneq_index;
> >  			addressLow = pmu->done_qbuffer[doneq_index &
> >  				0xFFF].addressLow;
> > @@ -2843,7 +2807,7 @@ static bool arcmsr_hbaD_get_config(struc
> >  	char __iomem *iop_firm_version;
> >  	char __iomem *iop_device_map;
> >  	u32 count;
> > -	struct MessageUnit_D *reg ;
> > +	struct MessageUnit_D *reg;
> >  	void *dma_coherent2;
> >  	dma_addr_t dma_coherent_handle2;
> >  	struct pci_dev *pdev = acb->pdev;
> > @@ -3176,7 +3140,7 @@ static int arcmsr_hbaD_polling_ccbdone(s
> >  {
> >  	bool error;
> >  	uint32_t poll_ccb_done = 0, poll_count = 0, flag_ccb, ccb_cdb_phy;
> > -	int rtn, doneq_index, index_stripped, outbound_write_pointer;
> > +	int rtn, doneq_index, index_stripped, outbound_write_pointer, toggle;
> >  	unsigned long flags;
> >  	struct ARCMSR_CDB *arcmsr_cdb;
> >  	struct CommandControlBlock *pCCB;
> > @@ -3185,9 +3149,11 @@ static int arcmsr_hbaD_polling_ccbdone(s
> >  polling_hbaD_ccb_retry:
> >  	poll_count++;
> >  	while (1) {
> > +		spin_lock_irqsave(&acb->doneq_lock, flags);
> >  		outbound_write_pointer = pmu->done_qbuffer[0].addressLow + 1;
> >  		doneq_index = pmu->doneq_index;
> >  		if ((outbound_write_pointer & 0xFFF) == (doneq_index & 0xFFF)) {
> > +			spin_unlock_irqrestore(&acb->doneq_lock, flags);
> >  			if (poll_ccb_done) {
> >  				rtn = SUCCESS;
> >  				break;
> > @@ -3200,21 +3166,11 @@ polling_hbaD_ccb_retry:
> >  				goto polling_hbaD_ccb_retry;
> >  			}
> >  		}
> > -		spin_lock_irqsave(&acb->doneq_lock, flags);
> > -		if (doneq_index & 0x4000) {
> > -			index_stripped = doneq_index & 0xFFF;
> > -			index_stripped += 1;
> > -			index_stripped %= ARCMSR_MAX_ARC1214_DONEQUEUE;
> > -			pmu->doneq_index = index_stripped ?
> > -				(index_stripped | 0x4000) :
> > -				(index_stripped + 1);
> > -		} else {
> > -			index_stripped = doneq_index;
> > -			index_stripped += 1;
> > -			index_stripped %= ARCMSR_MAX_ARC1214_DONEQUEUE;
> > -			pmu->doneq_index = index_stripped ? index_stripped :
> > -				((index_stripped | 0x4000) + 1);
> > -		}
> > +		toggle = doneq_index & 0x4000;
> > +		index_stripped = (doneq_index & 0xFFF) + 1;
> > +		index_stripped %= ARCMSR_MAX_ARC1214_DONEQUEUE;
> > +		pmu->doneq_index = index_stripped ? (index_stripped | toggle) :
> > +				((toggle ^ 0x4000) + 1);
> >  		spin_unlock_irqrestore(&acb->doneq_lock, flags);
> >  		doneq_index = pmu->doneq_index;
> >  		flag_ccb = pmu->done_qbuffer[doneq_index & 0xFFF].addressLow;
> >
> >
> > --
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