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authorK. Y. Srinivasan <kys@microsoft.com>2016-01-28 09:29:44 +0300
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2016-02-08 08:34:12 +0300
commit3eba9a77d5fc2cee486a16fff435686f024f61cf (patch)
treede72dc9b5edc88f242121f589ad33d37f76f747e /drivers
parent85d9aa705184a4504d0330017e3956fcdae8a9d6 (diff)
downloadlinux-3eba9a77d5fc2cee486a16fff435686f024f61cf.tar.xz
Drivers: hv: vmbus: Eliminate the spin lock on the read path
The function hv_ringbuffer_read() is called always on a pre-assigned CPU. Each chnnel is bound to a specific CPU and this function is always called on the CPU the channel is bound. There is no need to acquire the spin lock; get rid of this overhead. Signed-off-by: K. Y. Srinivasan <kys@microsoft.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers')
-rw-r--r--drivers/hv/ring_buffer.c18
1 files changed, 5 insertions, 13 deletions
diff --git a/drivers/hv/ring_buffer.c b/drivers/hv/ring_buffer.c
index b53702ce692f..1145f3b8e4e0 100644
--- a/drivers/hv/ring_buffer.c
+++ b/drivers/hv/ring_buffer.c
@@ -388,7 +388,6 @@ 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 +396,6 @@ 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 +410,7 @@ 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 +423,11 @@ 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);
@@ -460,7 +454,5 @@ int hv_ringbuffer_read(struct hv_ring_buffer_info *inring_info,
*signal = hv_need_to_signal_on_read(bytes_avail_towrite, inring_info);
-out_unlock:
- spin_unlock_irqrestore(&inring_info->ring_lock, flags);
return ret;
}