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Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Simon Horman , =?iso-8859-1?Q?Bj=F6rn_T=F6pel?= , Daniel Borkmann , Gal Pressman , Frederik Deweerdt , Martin Karsten , Tariq Toukan , Cosmin Ratiu , netdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH net v2] net: napi: Avoid gro timer misfiring at end of busypoll Message-ID: Mail-Followup-To: Joe Damato , Dragos Tatulea , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Simon Horman , =?iso-8859-1?Q?Bj=F6rn_T=F6pel?= , Daniel Borkmann , Gal Pressman , Frederik Deweerdt , Martin Karsten , Tariq Toukan , Cosmin Ratiu , netdev@vger.kernel.org, linux-kernel@vger.kernel.org References: <20260506090808.820559-2-dtatulea@nvidia.com> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260506090808.820559-2-dtatulea@nvidia.com> On Wed, May 06, 2026 at 09:08:08AM +0000, Dragos Tatulea wrote: > When in irq deferral mode (defer-hard-irqs > 0), a short enough > gro-flush timeout can trigger before NAPI_STATE_SCHED is cleared if the > last poll in busy_poll_stop() takes too long. This can have the effect > of leaving the queue stuck with interrupts disabled and no timer armed > which results in a tx timeout if there is no subsequent busypoll cycle. > > To prevent this, defer the gro-flush timer arm after the last poll. > > Fixes: 7fd3253a7de6 ("net: Introduce preferred busy-polling") > Co-developed-by: Martin Karsten > Signed-off-by: Martin Karsten > Signed-off-by: Dragos Tatulea > Reviewed-by: Tariq Toukan > Reviewed-by: Cosmin Ratiu > --- > Changes since RFC [1]: > - Sending only fix to net. > - Made commit message clearer and more succint. > - Fixed timer arming to happen after clearing the NAPI_STATE_SCHED bit > - Arm timer after clearing NAPI_STATE_SCHED and drop IRQ disable. > > [1] https://lore.kernel.org/all/20260428175134.1197036-3-dtatulea@nvidia.com/ > --- > net/core/dev.c | 21 ++++++++++++--------- > 1 file changed, 12 insertions(+), 9 deletions(-) Good catch on this bug. This fix looks right to me. Reviewed-by: Joe Damato