linux-kernel - RE: [PATCH] liquidio: make timeout HZ independent and readable

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Message-ID: <BN7PR07MB46733C753AD60F8FA58A7D79F3470@BN7PR07MB4673.namprd07.prod.outlook.com>
Date:   Fri, 6 Jul 2018 00:19:51 +0000
From:   "Chickles, Derek" <Derek.Chickles@...ium.com>
To:     Nicholas Mc Guire <hofrat@...dl.org>
CC:     "Burla, Satananda" <Satananda.Burla@...ium.com>,
        "Manlunas, Felix" <Felix.Manlunas@...ium.com>,
        "Vatsavayi, Raghu" <Raghu.Vatsavayi@...ium.com>,
        "David S. Miller" <davem@...emloft.net>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH] liquidio: make timeout HZ independent and readable

> From: Nicholas Mc Guire [mailto:hofrat@...dl.org]
> Sent: Monday, July 02, 2018 11:13 AM
> Subject: [PATCH] liquidio: make timeout HZ independent and readable
> 
> schedule_timeout_* takes a timeout in jiffies but the code currently is passing in
> a constant which makes this timeout HZ dependent. So define a constant with
> (hopefully) meaningful name and pass it through
> msecs_to_jiffies() to fix the HZ dependency.
> 
> Signed-off-by: Nicholas Mc Guire <hofrat@...dl.org> commit f21fb3ed364b
> ("Add support of Cavium Liquidio ethernet adapters")
> ---
> 
> Problem found by experimental coccinelle script
> 
> The current wait time can vary by a factor 10 depending on the HZ setting chose,
> which does not seem reasonable here.
> 
> The below patch sets the timeout to 1s - which is the current duration assuming
> a setting of HZ== 100. It is though not clear if this is the intent or if it should be
> shorter as it is not clear what HZ setting was assumed during design and used for
> testing.
> 
> This needs an ack by someone who knows the device and can confirm that
> waiting 1s for in-flight requests on device removal is reasonable.
> 
> Patch was compile tested with: x86_64_defconfig (implies
> CONFIG_NET_VENDOR_CAVIUM=y)
> (with a large number of sparse warnings though unrelated to the proposed
> change)
> 
> Patch is against 4.18-rc2 (localversion-next is -next-20180702)
> 
>  drivers/net/ethernet/cavium/liquidio/lio_main.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/net/ethernet/cavium/liquidio/lio_main.c
> b/drivers/net/ethernet/cavium/liquidio/lio_main.c
> index 7cb4e75..b2d0598 100644
> --- a/drivers/net/ethernet/cavium/liquidio/lio_main.c
> +++ b/drivers/net/ethernet/cavium/liquidio/lio_main.c
> @@ -91,6 +91,9 @@ static int octeon_console_debug_enabled(u32 console)
>   */
>  #define LIO_SYNC_OCTEON_TIME_INTERVAL_MS 60000
> 
> +/* time to wait for possible in-flight requests in milliseconds */
> +#define WAIT_INFLIGHT_REQUEST  msecs_to_jiffies(1000)
> +
>  struct lio_trusted_vf_ctx {
>         struct completion complete;
>         int status;
> @@ -259,7 +262,7 @@ static inline void pcierror_quiesce_device(struct
> octeon_device *oct)
>         force_io_queues_off(oct);
> 
>         /* To allow for in-flight requests */
> -       schedule_timeout_uninterruptible(100);
> +       schedule_timeout_uninterruptible(WAIT_INFLIGHT_REQUEST);
> 
>         if (wait_for_pending_requests(oct))
>                 dev_err(&oct->pci_dev->dev, "There were pending requests\n");
> --
> 2.1.4

Looks fine.

Acked-by: Derek Chickles <derek.chickles@...iumnetworks.com>