diff options
Diffstat (limited to 'drivers/hv/ring_buffer.c')
| -rw-r--r-- | drivers/hv/ring_buffer.c | 57 |
1 files changed, 33 insertions, 24 deletions
diff --git a/drivers/hv/ring_buffer.c b/drivers/hv/ring_buffer.c index b53702ce692f..a40a73a7b71d 100644 --- a/drivers/hv/ring_buffer.c +++ b/drivers/hv/ring_buffer.c @@ -103,15 +103,29 @@ 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 prev_write_sz, - struct hv_ring_buffer_info *rbi) +static bool hv_need_to_signal_on_read(struct hv_ring_buffer_info *rbi) { 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; + /* + * 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; @@ -120,7 +134,7 @@ static bool hv_need_to_signal_on_read(u32 prev_write_sz, cur_write_sz = write_loc >= read_loc ? r_size - (write_loc - read_loc) : read_loc - write_loc; - if ((prev_write_sz < pending_sz) && (cur_write_sz >= pending_sz)) + if (cur_write_sz >= pending_sz) return true; return false; @@ -314,7 +328,7 @@ void hv_ringbuffer_cleanup(struct hv_ring_buffer_info *ring_info) /* 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) + struct kvec *kv_list, u32 kv_count, bool *signal, bool lock) { int i = 0; u32 bytes_avail_towrite; @@ -324,14 +338,15 @@ int hv_ringbuffer_write(struct hv_ring_buffer_info *outring_info, u32 next_write_location; u32 old_write; u64 prev_indices = 0; - unsigned long flags; + unsigned long flags = 0; for (i = 0; i < kv_count; i++) totalbytes_towrite += kv_list[i].iov_len; totalbytes_towrite += sizeof(u64); - spin_lock_irqsave(&outring_info->ring_lock, flags); + if (lock) + spin_lock_irqsave(&outring_info->ring_lock, flags); hv_get_ringbuffer_availbytes(outring_info, &bytes_avail_toread, @@ -343,7 +358,8 @@ int hv_ringbuffer_write(struct hv_ring_buffer_info *outring_info, * is empty since the read index == write index. */ if (bytes_avail_towrite <= totalbytes_towrite) { - spin_unlock_irqrestore(&outring_info->ring_lock, flags); + if (lock) + spin_unlock_irqrestore(&outring_info->ring_lock, flags); return -EAGAIN; } @@ -374,7 +390,8 @@ int hv_ringbuffer_write(struct hv_ring_buffer_info *outring_info, hv_set_next_write_location(outring_info, next_write_location); - spin_unlock_irqrestore(&outring_info->ring_lock, flags); + if (lock) + spin_unlock_irqrestore(&outring_info->ring_lock, flags); *signal = hv_need_to_signal(old_write, outring_info); return 0; @@ -388,7 +405,6 @@ int hv_ringbuffer_read(struct hv_ring_buffer_info *inring_info, u32 bytes_avail_toread; u32 next_read_location = 0; u64 prev_indices = 0; - unsigned long flags; struct vmpacket_descriptor desc; u32 offset; u32 packetlen; @@ -397,7 +413,6 @@ int hv_ringbuffer_read(struct hv_ring_buffer_info *inring_info, if (buflen <= 0) return -EINVAL; - spin_lock_irqsave(&inring_info->ring_lock, flags); *buffer_actual_len = 0; *requestid = 0; @@ -412,7 +427,7 @@ int hv_ringbuffer_read(struct hv_ring_buffer_info *inring_info, * No error is set when there is even no header, drivers are * supposed to analyze buffer_actual_len. */ - goto out_unlock; + return ret; } next_read_location = hv_get_next_read_location(inring_info); @@ -425,15 +440,11 @@ int hv_ringbuffer_read(struct hv_ring_buffer_info *inring_info, *buffer_actual_len = packetlen; *requestid = desc.trans_id; - if (bytes_avail_toread < packetlen + offset) { - ret = -EAGAIN; - goto out_unlock; - } + if (bytes_avail_toread < packetlen + offset) + return -EAGAIN; - if (packetlen > buflen) { - ret = -ENOBUFS; - goto out_unlock; - } + if (packetlen > buflen) + return -ENOBUFS; next_read_location = hv_get_next_readlocation_withoffset(inring_info, offset); @@ -458,9 +469,7 @@ int hv_ringbuffer_read(struct hv_ring_buffer_info *inring_info, /* Update the read index */ hv_set_next_read_location(inring_info, next_read_location); - *signal = hv_need_to_signal_on_read(bytes_avail_towrite, inring_info); + *signal = hv_need_to_signal_on_read(inring_info); -out_unlock: - spin_unlock_irqrestore(&inring_info->ring_lock, flags); return ret; } |
