Re: [PATCH 2/2] staging: greybus/loopback: use ktime_get() for time intervals

From: Bryan O'Donoghue
Date: Fri Nov 03 2017 - 06:28:56 EST


On 02/11/17 14:32, Arnd Bergmann wrote:
This driver is the only one using the deprecated timeval_to_ns()
helper. Changing it from do_gettimeofday() to ktime_get() makes
the code more efficient, more robust against concurrent
settimeofday(), more accurate and lets us get rid of that helper
in the future.

Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
---
drivers/staging/greybus/loopback.c | 42 ++++++++++++++++----------------------
1 file changed, 18 insertions(+), 24 deletions(-)

diff --git a/drivers/staging/greybus/loopback.c b/drivers/staging/greybus/loopback.c
index 85046fb16aad..3d92638c424b 100644
--- a/drivers/staging/greybus/loopback.c
+++ b/drivers/staging/greybus/loopback.c
@@ -58,7 +58,7 @@ static struct gb_loopback_device gb_dev;
struct gb_loopback_async_operation {
struct gb_loopback *gb;
struct gb_operation *operation;
- struct timeval ts;
+ ktime_t ts;
struct timer_list timer;
struct list_head entry;
struct work_struct work;
@@ -81,7 +81,7 @@ struct gb_loopback {
atomic_t outstanding_operations;
/* Per connection stats */
- struct timeval ts;
+ ktime_t ts;
struct gb_loopback_stats latency;
struct gb_loopback_stats throughput;
struct gb_loopback_stats requests_per_second;
@@ -375,14 +375,9 @@ static u64 __gb_loopback_calc_latency(u64 t1, u64 t2)
return NSEC_PER_DAY - t2 + t1;
}
-static u64 gb_loopback_calc_latency(struct timeval *ts, struct timeval *te)
+static u64 gb_loopback_calc_latency(ktime_t ts, ktime_t te)
{
- u64 t1, t2;
-
- t1 = timeval_to_ns(ts);
- t2 = timeval_to_ns(te);
-
- return __gb_loopback_calc_latency(t1, t2);
+ return __gb_loopback_calc_latency(ktime_to_ns(ts), ktime_to_ns(te));
}
static int gb_loopback_operation_sync(struct gb_loopback *gb, int type,
@@ -390,10 +385,10 @@ static int gb_loopback_operation_sync(struct gb_loopback *gb, int type,
void *response, int response_size)
{
struct gb_operation *operation;
- struct timeval ts, te;
+ ktime_t ts, te;
int ret;
- do_gettimeofday(&ts);
+ ts = ktime_get();
operation = gb_operation_create(gb->connection, type, request_size,
response_size, GFP_KERNEL);
if (!operation)
@@ -421,10 +416,10 @@ static int gb_loopback_operation_sync(struct gb_loopback *gb, int type,
}
}
- do_gettimeofday(&te);
+ te = ktime_get();
/* Calculate the total time the message took */
- gb->elapsed_nsecs = gb_loopback_calc_latency(&ts, &te);
+ gb->elapsed_nsecs = gb_loopback_calc_latency(ts, te);
out_put_operation:
gb_operation_put(operation);
@@ -492,10 +487,10 @@ static void gb_loopback_async_operation_callback(struct gb_operation *operation)
{
struct gb_loopback_async_operation *op_async;
struct gb_loopback *gb;
- struct timeval te;
+ ktime_t te;
bool err = false;
- do_gettimeofday(&te);
+ te = ktime_get();
op_async = gb_loopback_operation_find(operation->id);
if (!op_async)
return;
@@ -512,8 +507,7 @@ static void gb_loopback_async_operation_callback(struct gb_operation *operation)
}
if (!err)
- gb->elapsed_nsecs = gb_loopback_calc_latency(&op_async->ts,
- &te);
+ gb->elapsed_nsecs = gb_loopback_calc_latency(op_async->ts, te);
if (op_async->pending) {
if (err)
@@ -608,7 +602,7 @@ static int gb_loopback_async_operation(struct gb_loopback *gb, int type,
list_add_tail(&op_async->entry, &gb_dev.list_op_async);
spin_unlock_irqrestore(&gb_dev.lock, flags);
- do_gettimeofday(&op_async->ts);
+ op_async->ts = ktime_get();
op_async->pending = true;
atomic_inc(&gb->outstanding_operations);
mutex_lock(&gb->mutex);
@@ -842,7 +836,7 @@ static void gb_loopback_reset_stats(struct gb_loopback *gb)
/* Should be initialized at least once per transaction set */
gb->apbridge_latency_ts = 0;
gb->gbphy_latency_ts = 0;
- memset(&gb->ts, 0, sizeof(struct timeval));
+ gb->ts = ktime_set(0, 0);
}
static void gb_loopback_update_stats(struct gb_loopback_stats *stats, u32 val)
@@ -925,15 +919,15 @@ static void gb_loopback_calculate_stats(struct gb_loopback *gb, bool error)
{
u64 nlat;
u32 lat;
- struct timeval te;
+ ktime_t te;
if (!error) {
gb->requests_completed++;
gb_loopback_calculate_latency_stats(gb);
}
- do_gettimeofday(&te);
- nlat = gb_loopback_calc_latency(&gb->ts, &te);
+ te = ktime_get();
+ nlat = gb_loopback_calc_latency(gb->ts, te);
if (nlat >= NSEC_PER_SEC || gb->iteration_count == gb->iteration_max) {
lat = gb_loopback_nsec_to_usec_latency(nlat);
@@ -1017,8 +1011,8 @@ static int gb_loopback_fn(void *data)
size = gb->size;
us_wait = gb->us_wait;
type = gb->type;
- if (gb->ts.tv_usec == 0 && gb->ts.tv_sec == 0)
- do_gettimeofday(&gb->ts);
+ if (ktime_to_ns(gb->ts) == 0)
+ gb->ts = ktime_get();
mutex_unlock(&gb->mutex);
/* Else operations to perform */


This one I'd like to test first.

I'll get back to you