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Date: Sat, 24 Sep 2022 13:11:31 -0700 From: Saeed Mahameed <saeedm@...dia.com> To: Leon Romanovsky <leon@...nel.org> Cc: "David S . Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>, Eric Dumazet <edumazet@...gle.com>, netdev@...r.kernel.org, Paolo Abeni <pabeni@...hat.com> Subject: Re: [PATCH net-next] net/mlx5: Make ASO poll CQ usable in atomic context On 24 Sep 21:51, Leon Romanovsky wrote: >On Sat, Sep 24, 2022 at 10:24:25AM -0700, Saeed Mahameed wrote: >> On 24 Sep 14:17, Leon Romanovsky wrote: >> > From: Leon Romanovsky <leonro@...dia.com> >> > >> > Poll CQ functions shouldn't sleep as they are called in atomic context. >> > The following splat appears once the mlx5_aso_poll_cq() is used in such >> > flow. >> > >> > BUG: scheduling while atomic: swapper/17/0/0x00000100 >> >> ... >> >> > /* With newer FW, the wait for the first ASO WQE is more than 2us, put the wait 10ms. */ >> > - err = mlx5_aso_poll_cq(aso, true, 10); >> > + expires = jiffies + msecs_to_jiffies(10); >> > + do { >> > + err = mlx5_aso_poll_cq(aso, true); >> > + } while (err && time_is_after_jiffies(expires)); >> > mutex_unlock(&flow_meters->aso_lock); >> ^^^^ >> busy poll won't work, this mutex is held and can sleep anyway. >> Let's discuss internally and solve this by design. > >This is TC code, it doesn't need atomic context and had mutex + sleep >from the beginning. > then let's bring back the sleep for TC use-case, we don't need to burn the CPU! But still the change has bigger effect on other aso use cases, see below. >My change cleans mlx5_aso_poll_cq() from busy loop for the IPsec path, >so why do you plan to change in the design? > a typical use case for aso is post_aso_wqe(); poll_aso_cqe(); The HW needs time to consume and excute the wqe then generate the CQE. This is why the driver needs to wait a bit when polling for the cqe, your change will break others. Let's discuss internally. >Thanks
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