2016-03-18 09:55:09

by Miaoqing Pan

Subject: [PATCH] ath9k: fix rng high cpu load

From: Miaoqing Pan <[email protected]>

If no valid ADC randomness output, ath9k rng will continuously
reading ADC, which will cause high CPU load. So increase the
delay to wait for ADC ready.

Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=114261
Signed-off-by: Miaoqing Pan <[email protected]>
---
drivers/net/wireless/ath/ath9k/rng.c | 20 +++++++++++++++++++-
1 file changed, 19 insertions(+), 1 deletion(-)

diff --git a/drivers/net/wireless/ath/ath9k/rng.c b/drivers/net/wireless/ath/ath9k/rng.c
index c9cb2aa..d38e50f 100644
--- a/drivers/net/wireless/ath/ath9k/rng.c
+++ b/drivers/net/wireless/ath/ath9k/rng.c
@@ -55,11 +55,26 @@ static int ath9k_rng_data_read(struct ath_softc *sc, u32 *buf, u32 buf_size)
return j << 2;
}

+static u32 ath9k_rng_delay_get(u32 fail_stats)
+{
+ u32 delay;
+
+ if (fail_stats < 100)
+ delay = 10;
+ else if (fail_stats < 105)
+ delay = 1000;
+ else
+ delay = 10000;
+
+ return delay;
+}
+
static int ath9k_rng_kthread(void *data)
{
int bytes_read;
struct ath_softc *sc = data;
u32 *rng_buf;
+ u32 delay, fail_stats = 0;

rng_buf = kmalloc_array(ATH9K_RNG_BUF_SIZE, sizeof(u32), GFP_KERNEL);
if (!rng_buf)
@@ -69,10 +84,13 @@ static int ath9k_rng_kthread(void *data)
bytes_read = ath9k_rng_data_read(sc, rng_buf,
ATH9K_RNG_BUF_SIZE);
if (unlikely(!bytes_read)) {
- msleep_interruptible(10);
+ delay = ath9k_rng_delay_get(++fail_stats);
+ msleep_interruptible(delay);
continue;
}

+ fail_stats = 0;
+
/* sleep until entropy bits under write_wakeup_threshold */
add_hwgenerator_randomness((void *)rng_buf, bytes_read,
ATH9K_RNG_ENTROPY(bytes_read));
--
1.9.1

2016-04-06 18:21:22

by Kalle Valo

Subject: Re: [PATCH] ath9k: fix rng high cpu load

[email protected] writes:

> From: Miaoqing Pan <[email protected]>
>
> If no valid ADC randomness output, ath9k rng will continuously
> reading ADC, which will cause high CPU load. So increase the
> delay to wait for ADC ready.
>
> Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=114261
> Signed-off-by: Miaoqing Pan <[email protected]>

Applied, thanks.

--
Kalle Valo