Rather than busy loop waiting to drain I/O, introduce a function that does not burn CPU cycles waiting.
Signed-off-by: K. Y. Srinivasan <[email protected]> Signed-off-by: Haiyang Zhang <[email protected]> Signed-off-by: Abhishek Kane <[email protected]> Signed-off-by: Hank Janssen <[email protected]> --- drivers/staging/hv/storvsc.c | 6 +++++- drivers/staging/hv/storvsc_api.h | 12 ++++++++++++ 2 files changed, 17 insertions(+), 1 deletions(-) diff --git a/drivers/staging/hv/storvsc.c b/drivers/staging/hv/storvsc.c index 8ee1ad0..36458b8 100644 --- a/drivers/staging/hv/storvsc.c +++ b/drivers/staging/hv/storvsc.c @@ -47,6 +47,7 @@ static inline struct storvsc_device *alloc_stor_device(struct hv_device *device) /* (ie get_stor_device() and must_get_stor_device()) to proceed. */ atomic_cmpxchg(&stor_device->ref_count, 0, 2); + init_waitqueue_head(&stor_device->waiting_to_drain); stor_device->device = device; device->ext = stor_device; @@ -332,7 +333,10 @@ static void stor_vsc_on_io_completion(struct hv_device *device, request->on_io_completion(request); - atomic_dec(&stor_device->num_outstanding_req); + if (atomic_dec_and_test(&stor_device->num_outstanding_req) && + stor_device->drain_notify) + wake_up(&stor_device->waiting_to_drain); + put_stor_device(device); } diff --git a/drivers/staging/hv/storvsc_api.h b/drivers/staging/hv/storvsc_api.h index 32228c0..1887940 100644 --- a/drivers/staging/hv/storvsc_api.h +++ b/drivers/staging/hv/storvsc_api.h @@ -26,6 +26,7 @@ #define _STORVSC_API_H_ #include <linux/kernel.h> +#include <linux/wait.h> #include "vstorage.h" #include "vmbus_api.h" #include "vmbus.h" @@ -108,8 +109,11 @@ struct storvsc_device { /* 0 indicates the device is being destroyed */ atomic_t ref_count; + bool drain_notify; atomic_t num_outstanding_req; + wait_queue_head_t waiting_to_drain; + /* * Each unique Port/Path/Target represents 1 channel ie scsi * controller. In reality, the pathid, targetid is always 0 @@ -161,6 +165,14 @@ struct storvsc_driver *drv_to_stordrv(struct device_driver *d) return hvdr_to_stordr(hvdrv); } +static inline void storvsc_wait_to_drain(struct storvsc_device *dev) +{ + dev->drain_notify = true; + wait_event(dev->waiting_to_drain, + atomic_read(&dev->num_outstanding_req) == 0); + dev->drain_notify = false; +} + /* Interface */ int storvsc_dev_add(struct hv_device *device, -- 1.7.4.1 _______________________________________________ devel mailing list [email protected] http://driverdev.linuxdriverproject.org/mailman/listinfo/devel
