diff options
Diffstat (limited to 'drivers/hv/ring_buffer.c')
| -rw-r--r-- | drivers/hv/ring_buffer.c | 165 |
1 files changed, 44 insertions, 121 deletions
diff --git a/drivers/hv/ring_buffer.c b/drivers/hv/ring_buffer.c index 6361d124f67d..14d45c70056e 100644 --- a/drivers/hv/ring_buffer.c +++ b/drivers/hv/ring_buffer.c @@ -103,19 +103,30 @@ static bool hv_need_to_signal(u32 old_write, struct hv_ring_buffer_info *rbi) * there is room for the producer to send the pending packet. */ -static bool hv_need_to_signal_on_read(u32 old_rd, - struct hv_ring_buffer_info *rbi) +static bool hv_need_to_signal_on_read(struct hv_ring_buffer_info *rbi) { - u32 prev_write_sz; u32 cur_write_sz; u32 r_size; - u32 write_loc = rbi->ring_buffer->write_index; + u32 write_loc; u32 read_loc = rbi->ring_buffer->read_index; - u32 pending_sz = rbi->ring_buffer->pending_send_sz; + u32 pending_sz; /* - * If the other end is not blocked on write don't bother. + * Issue a full memory barrier before making the signaling decision. + * Here is the reason for having this barrier: + * If the reading of the pend_sz (in this function) + * were to be reordered and read before we commit the new read + * index (in the calling function) we could + * have a problem. If the host were to set the pending_sz after we + * have sampled pending_sz and go to sleep before we commit the + * read index, we could miss sending the interrupt. Issue a full + * memory barrier to address this. */ + mb(); + + pending_sz = rbi->ring_buffer->pending_send_sz; + write_loc = rbi->ring_buffer->write_index; + /* If the other end is not blocked on write don't bother. */ if (pending_sz == 0) return false; @@ -123,22 +134,13 @@ static bool hv_need_to_signal_on_read(u32 old_rd, cur_write_sz = write_loc >= read_loc ? r_size - (write_loc - read_loc) : read_loc - write_loc; - prev_write_sz = write_loc >= old_rd ? r_size - (write_loc - old_rd) : - old_rd - write_loc; - - - if ((prev_write_sz < pending_sz) && (cur_write_sz >= pending_sz)) + if (cur_write_sz >= pending_sz) return true; return false; } -/* - * hv_get_next_write_location() - * - * Get the next write location for the specified ring buffer - * - */ +/* Get the next write location for the specified ring buffer. */ static inline u32 hv_get_next_write_location(struct hv_ring_buffer_info *ring_info) { @@ -147,12 +149,7 @@ hv_get_next_write_location(struct hv_ring_buffer_info *ring_info) return next; } -/* - * hv_set_next_write_location() - * - * Set the next write location for the specified ring buffer - * - */ +/* Set the next write location for the specified ring buffer. */ static inline void hv_set_next_write_location(struct hv_ring_buffer_info *ring_info, u32 next_write_location) @@ -160,11 +157,7 @@ hv_set_next_write_location(struct hv_ring_buffer_info *ring_info, ring_info->ring_buffer->write_index = next_write_location; } -/* - * hv_get_next_read_location() - * - * Get the next read location for the specified ring buffer - */ +/* Get the next read location for the specified ring buffer. */ static inline u32 hv_get_next_read_location(struct hv_ring_buffer_info *ring_info) { @@ -174,10 +167,8 @@ hv_get_next_read_location(struct hv_ring_buffer_info *ring_info) } /* - * hv_get_next_readlocation_withoffset() - * * Get the next read location + offset for the specified ring buffer. - * This allows the caller to skip + * This allows the caller to skip. */ static inline u32 hv_get_next_readlocation_withoffset(struct hv_ring_buffer_info *ring_info, @@ -191,13 +182,7 @@ hv_get_next_readlocation_withoffset(struct hv_ring_buffer_info *ring_info, return next; } -/* - * - * hv_set_next_read_location() - * - * Set the next read location for the specified ring buffer - * - */ +/* Set the next read location for the specified ring buffer. */ static inline void hv_set_next_read_location(struct hv_ring_buffer_info *ring_info, u32 next_read_location) @@ -206,12 +191,7 @@ hv_set_next_read_location(struct hv_ring_buffer_info *ring_info, } -/* - * - * hv_get_ring_buffer() - * - * Get the start of the ring buffer - */ +/* Get the start of the ring buffer. */ static inline void * hv_get_ring_buffer(struct hv_ring_buffer_info *ring_info) { @@ -219,25 +199,14 @@ hv_get_ring_buffer(struct hv_ring_buffer_info *ring_info) } -/* - * - * hv_get_ring_buffersize() - * - * Get the size of the ring buffer - */ +/* Get the size of the ring buffer. */ static inline u32 hv_get_ring_buffersize(struct hv_ring_buffer_info *ring_info) { return ring_info->ring_datasize; } -/* - * - * hv_get_ring_bufferindices() - * - * Get the read and write indices as u64 of the specified ring buffer - * - */ +/* Get the read and write indices as u64 of the specified ring buffer. */ static inline u64 hv_get_ring_bufferindices(struct hv_ring_buffer_info *ring_info) { @@ -245,12 +214,8 @@ hv_get_ring_bufferindices(struct hv_ring_buffer_info *ring_info) } /* - * - * hv_copyfrom_ringbuffer() - * * Helper routine to copy to source from ring buffer. * Assume there is enough room. Handles wrap-around in src case only!! - * */ static u32 hv_copyfrom_ringbuffer( struct hv_ring_buffer_info *ring_info, @@ -282,12 +247,8 @@ static u32 hv_copyfrom_ringbuffer( /* - * - * hv_copyto_ringbuffer() - * * Helper routine to copy from source to ring buffer. * Assume there is enough room. Handles wrap-around in dest case only!! - * */ static u32 hv_copyto_ringbuffer( struct hv_ring_buffer_info *ring_info, @@ -313,13 +274,7 @@ static u32 hv_copyto_ringbuffer( return start_write_offset; } -/* - * - * hv_ringbuffer_get_debuginfo() - * - * Get various debug metrics for the specified ring buffer - * - */ +/* Get various debug metrics for the specified ring buffer. */ void hv_ringbuffer_get_debuginfo(struct hv_ring_buffer_info *ring_info, struct hv_ring_buffer_debug_info *debug_info) { @@ -342,13 +297,7 @@ void hv_ringbuffer_get_debuginfo(struct hv_ring_buffer_info *ring_info, } } -/* - * - * hv_ringbuffer_init() - * - *Initialize the ring buffer - * - */ +/* Initialize the ring buffer. */ int hv_ringbuffer_init(struct hv_ring_buffer_info *ring_info, void *buffer, u32 buflen) { @@ -361,9 +310,7 @@ int hv_ringbuffer_init(struct hv_ring_buffer_info *ring_info, ring_info->ring_buffer->read_index = ring_info->ring_buffer->write_index = 0; - /* - * Set the feature bit for enabling flow control. - */ + /* Set the feature bit for enabling flow control. */ ring_info->ring_buffer->feature_bits.value = 1; ring_info->ring_size = buflen; @@ -374,24 +321,12 @@ int hv_ringbuffer_init(struct hv_ring_buffer_info *ring_info, return 0; } -/* - * - * hv_ringbuffer_cleanup() - * - * Cleanup the ring buffer - * - */ +/* Cleanup the ring buffer. */ void hv_ringbuffer_cleanup(struct hv_ring_buffer_info *ring_info) { } -/* - * - * hv_ringbuffer_write() - * - * Write to the ring buffer - * - */ +/* Write to the ring buffer. */ int hv_ringbuffer_write(struct hv_ring_buffer_info *outring_info, struct kvec *kv_list, u32 kv_count, bool *signal) { @@ -416,10 +351,11 @@ int hv_ringbuffer_write(struct hv_ring_buffer_info *outring_info, &bytes_avail_toread, &bytes_avail_towrite); - - /* If there is only room for the packet, assume it is full. */ - /* Otherwise, the next time around, we think the ring buffer */ - /* is empty since the read index == write index */ + /* + * If there is only room for the packet, assume it is full. + * Otherwise, the next time around, we think the ring buffer + * is empty since the read index == write index. + */ if (bytes_avail_towrite <= totalbytes_towrite) { spin_unlock_irqrestore(&outring_info->ring_lock, flags); return -EAGAIN; @@ -459,13 +395,7 @@ int hv_ringbuffer_write(struct hv_ring_buffer_info *outring_info, } -/* - * - * hv_ringbuffer_peek() - * - * Read without advancing the read index - * - */ +/* Read without advancing the read index. */ int hv_ringbuffer_peek(struct hv_ring_buffer_info *Inring_info, void *Buffer, u32 buflen) { @@ -502,13 +432,7 @@ int hv_ringbuffer_peek(struct hv_ring_buffer_info *Inring_info, } -/* - * - * hv_ringbuffer_read() - * - * Read and advance the read index - * - */ +/* Read and advance the read index. */ int hv_ringbuffer_read(struct hv_ring_buffer_info *inring_info, void *buffer, u32 buflen, u32 offset, bool *signal) { @@ -517,7 +441,6 @@ int hv_ringbuffer_read(struct hv_ring_buffer_info *inring_info, void *buffer, u32 next_read_location = 0; u64 prev_indices = 0; unsigned long flags; - u32 old_read; if (buflen <= 0) return -EINVAL; @@ -528,8 +451,6 @@ int hv_ringbuffer_read(struct hv_ring_buffer_info *inring_info, void *buffer, &bytes_avail_toread, &bytes_avail_towrite); - old_read = bytes_avail_toread; - /* Make sure there is something to read */ if (bytes_avail_toread < buflen) { spin_unlock_irqrestore(&inring_info->ring_lock, flags); @@ -550,9 +471,11 @@ int hv_ringbuffer_read(struct hv_ring_buffer_info *inring_info, void *buffer, sizeof(u64), next_read_location); - /* Make sure all reads are done before we update the read index since */ - /* the writer may start writing to the read area once the read index */ - /*is updated */ + /* + * Make sure all reads are done before we update the read index since + * the writer may start writing to the read area once the read index + * is updated. + */ mb(); /* Update the read index */ @@ -560,7 +483,7 @@ int hv_ringbuffer_read(struct hv_ring_buffer_info *inring_info, void *buffer, spin_unlock_irqrestore(&inring_info->ring_lock, flags); - *signal = hv_need_to_signal_on_read(old_read, inring_info); + *signal = hv_need_to_signal_on_read(inring_info); return 0; } |