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Commit c2faa05d authored by Wesley W. Terpstra's avatar Wesley W. Terpstra
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wishbone: remove mutex use from interrupt handler 

Previously, the interrupt handler popped the data from the hardware.
To do this, it needed to lock the target buffers, guarded by a mutex.
Unfortunately, that can cause the interrupt handler to sleep! bad!

This patch moves the waitq and fasync structure to the wishbone structure
which is always present.  Then, the interrupt handler need only wake up any
threads blocked waiting for data.  The read/poll functions invoke the
processing of data from the hardware, instead.
parent de8e86da
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Showing with 33 additions and 56 deletions
pcie-wb/wishbone.c
View file @ c2faa05d
......@@ -231,30 +231,30 @@ static void etherbone_master_process(struct etherbone_master_context* context)
static void etherbone_slave_out_process(struct etherbone_slave_context *context)
{
struct wishbone_request request;
uint8_t *wptr;
if (context->rbuf_done != context->rbuf_end) return;
if (!context->ready) {
if (!context->wishbone->wops->request(context->wishbone, &context->request)) return;
++context->pending_err;
if (context->rbuf_done != context->rbuf_end || /* unread data? */
!context->wishbone->wops->request(context->wishbone, &request)) {
return;
}
context->ready = 0;
++context->pending_err;
context->rbuf_done = 0;
wptr = &context->rbuf[0];
wptr[0] = ETHERBONE_BCA;
wptr[1] = context->request.mask;
wptr[1] = request.mask;
if (context->request.write) {
if (request.write) {
wptr[2] = 1;
wptr[3] = 0;
wptr += sizeof(wb_data_t);
eb_from_cpu(wptr, context->request.addr);
eb_from_cpu(wptr, request.addr);
wptr += sizeof(wb_data_t);
eb_from_cpu(wptr, context->request.data);
eb_from_cpu(wptr, request.data);
wptr += sizeof(wb_data_t);
} else {
wptr[2] = 0;
......@@ -262,7 +262,7 @@ static void etherbone_slave_out_process(struct etherbone_slave_context *context)
wptr += sizeof(wb_data_t);
eb_from_cpu(wptr, WBA_DATA);
wptr += sizeof(wb_data_t);
eb_from_cpu(wptr, context->request.addr);
eb_from_cpu(wptr, request.addr);
wptr += sizeof(wb_data_t);
}
......@@ -490,30 +490,8 @@ static const struct file_operations etherbone_master_fops = {
void wishbone_slave_ready(struct wishbone* wb)
{
mutex_lock(&wb->mutex);
if (wb->slave) {
struct etherbone_slave_context *context = wb->slave;
int ready;
/* If the slave is not already ready, make it ready! */
mutex_lock(&context->mutex);
if (!context->ready) {
/* Retrieve request */
ready = wb->wops->request(wb, &context->request);
context->ready = ready;
context->pending_err += ready;
etherbone_slave_out_process(context);
/* Wake-up polling descriptors */
mutex_unlock(&context->mutex);
wake_up_interruptible(&context->waitq);
kill_fasync(&context->fasync, SIGIO, POLL_IN);
} else {
mutex_unlock(&context->mutex);
}
}
mutex_unlock(&wb->mutex);
wake_up_interruptible(&wb->waitq);
kill_fasync(&wb->fasync, SIGIO, POLL_IN);
}
static int char_slave_open(struct inode *inode, struct file *filep)
......@@ -524,9 +502,7 @@ static int char_slave_open(struct inode *inode, struct file *filep)
if (!context) return -ENOMEM;
context->wishbone = container_of(inode->i_cdev, struct wishbone, slave_cdev);
context->fasync = 0;
mutex_init(&context->mutex);
init_waitqueue_head(&context->waitq);
filep->private_data = context;
......@@ -540,7 +516,6 @@ static int char_slave_open(struct inode *inode, struct file *filep)
context->wishbone->slave = context;
/* Setup Etherbone state machine */
context->ready = 0;
context->pending_err = 0;
context->negotiated = 0;
context->rbuf_done = 0;
......@@ -554,9 +529,6 @@ static int char_slave_open(struct inode *inode, struct file *filep)
memset(&context->rbuf[4], 0, 4);
context->rbuf_end = 8;
/* Must hold this lock until slave is fully setup,
* else wishbone_slave_ready could stomp on us.
*/
mutex_unlock(&context->wishbone->mutex);
return 0;
......@@ -566,24 +538,24 @@ static int char_slave_release(struct inode *inode, struct file *filep)
{
struct etherbone_slave_context *context = filep->private_data;
const struct wishbone_operations *wops = context->wishbone->wops;
int pending;
int pending, errors;
/* Lock order must match wishbone_slave_ready to prevent deadlock */
mutex_lock(&context->wishbone->mutex);
mutex_lock(&context->mutex);
/* We need to answer any requests pending, even if the bad user did not */
for (pending = context->pending_err; pending > 0; --pending)
errors = context->pending_err;
for (pending = errors; pending > 0; --pending)
wops->reply(context->wishbone, 1, 0);
mutex_lock(&context->wishbone->mutex);
context->wishbone->slave = 0;
mutex_unlock(&context->wishbone->mutex);
mutex_unlock(&context->mutex);
mutex_unlock(&context->wishbone->mutex);
kfree(context);
if (pending) return -EIO;
if (errors) return -EIO;
return 0;
}
......@@ -599,6 +571,8 @@ static ssize_t char_slave_aio_read(struct kiocb *iocb, const struct iovec *iov,
if (mutex_lock_interruptible(&context->mutex))
return -EINTR;
etherbone_slave_out_process(context);
buf_len = context->rbuf_end - context->rbuf_done;
if (buf_len > iov_len) {
len = iov_len;
......@@ -609,7 +583,6 @@ static ssize_t char_slave_aio_read(struct kiocb *iocb, const struct iovec *iov,
memcpy_toiovecend(iov, context->rbuf + context->rbuf_done, 0, len);
context->rbuf_done += len;
etherbone_slave_out_process(context);
mutex_unlock(&context->mutex);
if (len == 0 && (filep->f_flags & O_NONBLOCK) != 0)
......@@ -692,9 +665,10 @@ static unsigned int char_slave_poll(struct file *filep, poll_table *wait)
struct etherbone_slave_context *context = filep->private_data;
unsigned int mask;
poll_wait(filep, &context->waitq, wait);
poll_wait(filep, &context->wishbone->waitq, wait);
mutex_lock(&context->mutex);
etherbone_slave_out_process(context);
if (context->rbuf_done != context->rbuf_end) {
mask = POLLIN | POLLRDNORM | POLLOUT | POLLWRNORM;
......@@ -712,7 +686,7 @@ static int char_slave_fasync(int fd, struct file *file, int on)
struct etherbone_slave_context* context = file->private_data;
/* No locking - fasync_helper does its own locking */
return fasync_helper(fd, file, on, &context->fasync);
return fasync_helper(fd, file, on, &context->wishbone->fasync);
}
static const struct file_operations etherbone_slave_fops = {
......@@ -762,6 +736,8 @@ int wishbone_register(struct wishbone* wb)
}
}
init_waitqueue_head(&wb->waitq);
wb->fasync = 0;
mutex_init(&wb->mutex);
wb->slave = 0;
......
pcie-wb/wishbone.h
View file @ c2faa05d
......@@ -44,7 +44,7 @@ struct wishbone_operations
wb_data_t (*read_cfg)(struct wishbone *wb, wb_addr_t addr);
/* slave operations */
int (*request)(struct wishbone *wb, struct wishbone_request*); /* 1=record filled, 0=none pending */
int (*request)(struct wishbone *wb, struct wishbone_request*); /* 1=record filled, 0=none pending. re-enable non-MSI interrupts. */
void (*reply)(struct wishbone *wb, int err, wb_data_t dat);
};
......@@ -59,6 +59,10 @@ struct wishbone
dev_t master_dev, slave_dev;
struct cdev master_cdev, slave_cdev;
struct device *master_device, *slave_device;
/* wake-q for blocking slave io */
wait_queue_head_t waitq;
struct fasync_struct *fasync;
struct mutex mutex; /* guards slave below */
struct etherbone_slave_context *slave;
};
......@@ -84,12 +88,8 @@ struct etherbone_master_context
struct etherbone_slave_context
{
struct wishbone* wishbone;
struct fasync_struct *fasync;
struct mutex mutex;
wait_queue_head_t waitq;
struct wishbone_request request;
int ready; /* if request is full */
unsigned int pending_err; /* unanswered operations */
int negotiated;
......@@ -111,6 +111,7 @@ struct etherbone_slave_context
int wishbone_register(struct wishbone* wb);
int wishbone_unregister(struct wishbone* wb);
void wishbone_slave_ready(struct wishbone* wb); /* called when device has data pending */
/* call when device has data pending. disable non-MSI interrupt generation before calling. */
void wishbone_slave_ready(struct wishbone* wb);
#endif
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