[PATCH V4 2/9] aacraid: Fix RRQ overload

Raghava Aditya Renukunta
2016-01-29T22:35:40Z

The driver utilizes an array of atomic variables to keep track of
IO submissions to each vector. To submit an IO multiple threads
iterate through the array to find a vector which has empty slots
to send an IO. The reading and updating of the variable is not atomic,
causing race conditions when a thread uses a full vector to
submit an IO.

Fixed by mapping each FIB to a vector, the submission path then uses
said vector to submit IO thereby removing the possibly of a race
condition.The vector assignment is started from 1 since vector 0 is
reserved for the use of AIF management FIBS.If the number of MSIx
vectors is 1 (MSI or INTx mode) then all the fibs are allocated to
vector 0.

Changes in V2:
Created function aac_fib_vector_assign to assign vector numbers to
fib and to prevent code duplication

Changes in V3:
None

Changes in V4:
None

Fixes: 495c0217 "aacraid: MSI-x support"
Cc: stable@vger.kernel.org # v4.1

Signed-off-by: Raghava Aditya Renukunta <raghavaaditya.renukunta@pmcs.com>
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Reviewed-by: Tomas Henzl <thenzl@redhat.com>
---
drivers/scsi/aacraid/aacraid.h | 2 ++
drivers/scsi/aacraid/commsup.c | 28 ++++++++++++++++++++++++++++
drivers/scsi/aacraid/src.c | 30 +++++++-----------------------
3 files changed, 37 insertions(+), 23 deletions(-)

diff --git a/drivers/scsi/aacraid/aacraid.h b/drivers/scsi/aacraid/aacraid.h
index f51f0a0..fff1306 100644
--- a/drivers/scsi/aacraid/aacraid.h
+++ b/drivers/scsi/aacraid/aacraid.h
@@ -944,6 +944,7 @@ struct fib {
*/
struct list_head fiblink;
void *data;
+ u32 vector_no;
struct hw_fib *hw_fib_va; /* Actual shared object */
dma_addr_t hw_fib_pa; /* physical address of hw_fib*/
};
@@ -2113,6 +2114,7 @@ static inline unsigned int cap_to_cyls(sector_t capacity, unsigned divisor)
int aac_acquire_irq(struct aac_dev *dev);
void aac_free_irq(struct aac_dev *dev);
const char *aac_driverinfo(struct Scsi_Host *);
+void aac_fib_vector_assign(struct aac_dev *dev);
struct fib *aac_fib_alloc(struct aac_dev *dev);
struct fib *aac_fib_alloc_tag(struct aac_dev *dev, struct scsi_cmnd *scmd);
int aac_fib_setup(struct aac_dev *dev);
diff --git a/drivers/scsi/aacraid/commsup.c b/drivers/scsi/aacraid/commsup.c
index 46a2a2f..07a42a3 100644
--- a/drivers/scsi/aacraid/commsup.c
+++ b/drivers/scsi/aacraid/commsup.c
@@ -90,6 +90,28 @@ void aac_fib_map_free(struct aac_dev *dev)
dev->hw_fib_pa = 0;
}

+void aac_fib_vector_assign(struct aac_dev *dev)
+{
+ u32 i = 0;
+ u32 vector = 1;
+ struct fib *fibptr = NULL;
+
+ for (i = 0, fibptr = &dev->fibs[i];
+ i < (dev->scsi_host_ptr->can_queue + AAC_NUM_MGT_FIB);
+ i++, fibptr++) {
+ if ((dev->max_msix == 1) ||
+ (i > ((dev->scsi_host_ptr->can_queue + AAC_NUM_MGT_FIB - 1)
+ - dev->vector_cap))) {
+ fibptr->vector_no = 0;
+ } else {
+ fibptr->vector_no = vector;
+ vector++;
+ if (vector == dev->max_msix)
+ vector = 1;
+ }
+ }
+}
+
/**
* aac_fib_setup - setup the fibs
* @dev: Adapter to set up
@@ -152,6 +174,12 @@ int aac_fib_setup(struct aac_dev * dev)
hw_fib_pa = hw_fib_pa +
dev->max_fib_size + sizeof(struct aac_fib_xporthdr);
}
+
+ /*
+ *Assign vector numbers to fibs
+ */
+ aac_fib_vector_assign(dev);
+
/*
* Add the fib chain to the free list
*/
diff --git a/drivers/scsi/aacraid/src.c b/drivers/scsi/aacraid/src.c
index 2aa34ea..bc0203f 100644
--- a/drivers/scsi/aacraid/src.c
+++ b/drivers/scsi/aacraid/src.c
@@ -156,8 +156,8 @@ static irqreturn_t aac_src_intr_message(int irq, void *dev_id)
break;
if (dev->msi_enabled && dev->max_msix > 1)
atomic_dec(&dev->rrq_outstanding[vector_no]);
- aac_intr_normal(dev, handle-1, 0, isFastResponse, NULL);
dev->host_rrq[index++] = 0;
+ aac_intr_normal(dev, handle-1, 0, isFastResponse, NULL);
if (index == (vector_no + 1) * dev->vector_cap)
index = vector_no * dev->vector_cap;
dev->host_rrq_idx[vector_no] = index;
@@ -452,36 +452,20 @@ static int aac_src_deliver_message(struct fib *fib)
#endif

u16 hdr_size = le16_to_cpu(fib->hw_fib_va->header.Size);
+ u16 vector_no;

atomic_inc(&q->numpending);

if (dev->msi_enabled && fib->hw_fib_va->header.Command != AifRequest &&
dev->max_msix > 1) {
- u_int16_t vector_no, first_choice = 0xffff;
-
- vector_no = dev->fibs_pushed_no % dev->max_msix;
- do {
- vector_no += 1;
- if (vector_no == dev->max_msix)
- vector_no = 1;
- if (atomic_read(&dev->rrq_outstanding[vector_no]) <
- dev->vector_cap)
- break;
- if (0xffff == first_choice)
- first_choice = vector_no;
- else if (vector_no == first_choice)
- break;
- } while (1);
- if (vector_no == first_choice)
- vector_no = 0;
- atomic_inc(&dev->rrq_outstanding[vector_no]);
- if (dev->fibs_pushed_no == 0xffffffff)
- dev->fibs_pushed_no = 0;
- else
- dev->fibs_pushed_no++;
+ vector_no = fib->vector_no;
fib->hw_fib_va->header.Handle += (vector_no << 16);
+ } else {
+ vector_no = 0;
}

+ atomic_inc(&dev->rrq_outstanding[vector_no]);
+
if (dev->comm_interface == AAC_COMM_MESSAGE_TYPE2) {
/* Calculate the amount to the fibsize bits */
fibsize = (hdr_size + 127) / 128 - 1;
--
1.9.1