From 3eba9a77d5fc2cee486a16fff435686f024f61cf Mon Sep 17 00:00:00 2001 From: "K. Y. Srinivasan" Date: Wed, 27 Jan 2016 22:29:44 -0800 Subject: [PATCH] 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 Signed-off-by: Greg Kroah-Hartman --- drivers/hv/ring_buffer.c | 18 +++++------------- 1 file 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; } -- 2.30.2