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McKenney" Cc: Tejun Heo , Andrea Righi , sched-ext@lists.linux.dev, linux-kernel@vger.kernel.org, kernel-team@cloudflare.com Subject: Re: sched_ext/lavd hard lockup in old call_rcu_tasks_generic needadjust path Message-ID: References: <20260609104733.1184001-1-mfleming@cloudflare.com> <2179fc11-3bd5-4d2e-9ad8-609e3356ec09@paulmck-laptop> <1ad83f53-7897-40bc-a503-5a71031aa27f@paulmck-laptop> <3bbd4298-eb01-4784-bee5-caab3d3647b9@paulmck-laptop> <35337ded-add4-4689-8f61-73f583a69b36@paulmck-laptop> Precedence: bulk X-Mailing-List: linux-kernel@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: <35337ded-add4-4689-8f61-73f583a69b36@paulmck-laptop> On Tue, Jun 16, 2026 at 08:24:55PM -0700, Paul E. McKenney wrote: > On Tue, Jun 16, 2026 at 11:56:19AM +0100, Matt Fleming wrote: > > > > What about something like this? > > Not bad, actually. > > But we are going to have to similarly bypass call_rcu_tasks_generic() > soon enough, though only when interrupts are disabled at the time > of the call. One complication is that it would need to interact > with rcu_barrier_tasks_generic(), which would need to remove any > pending callbacks from bypassed call_rcu_tasks_generic() invocations, > as in llist_del_all() and enqueue the callbacks. A well-placed > raw_spin_trylock_rcu_node(rtpcp) should suffice for the serialization. > The trick is that rcu_barrier_tasks_generic() is not obligated to > wait on later calls to call_rcu_tasks_generic(). > > Is this something that you would be interested in digging into? Sure, I'll take a look. Thanks, Matt