From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 7B1234582FD; Wed, 22 Jul 2026 23:36:06 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784763367; cv=none; b=C/iWrTQ+elcFn4jWHV+Zc94bU8GHDRBZFgTmII3RuBWgXLzwgv+SK9xxHuLQ06Q0UWBKXe5h0qkCR9e70T6Zg0DtXt2ogDRKF+BEkg0PC2jstqGJUyKLsoGnxOeN0e1vYWY4+fXi7oTL7mkDSRWm0qj+z4oqthSMBWEtiYSUnOg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784763367; c=relaxed/simple; bh=IfWkqpeBfLBAuv9N/WhfKP/zkHXbOKcMJBQm3autBDA=; h=Message-ID:From:To:Cc:Subject:Date:In-Reply-To:References; b=se4ta0OUWzwCU9Luc8LM7IucuuM+fo0RIdenz2E4sQvLEs0c1oJYg5piAQzWc2OnbmJa1mpK3nwujonpBe85+kZFhvGUTLYTAh+ZM4cUaBBx2vACFhIB28yPjpZ2zF+k2nahVe7TCZsd2WTXbxqInpSngDPy1XdXWyMxT+U3K9g= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=OwQjG/0z; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="OwQjG/0z" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 0378D1F00A3F; Wed, 22 Jul 2026 23:36:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1784763366; bh=swFuh1PPk6kgwBS+ydO+DRiGQfnSWFxZZ/hCz10i32E=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=OwQjG/0z+qooG3ikw63aVQjoLA2JFUOlIHlzBv6Db8hgYaegL/Qw2JwxrbIV+JUTF I0bupjtRiTVWGWREpIPG7D7GNfN3k2p/dF9X9e81r8ZT8wo5dhmcA7gX1I1ndoy+73 uNZhDVMsEQUfrD/kerynB8wPEa97Jsvrywg1gB49TAbE+UqAn7o5m86+o+Ra1LBePI m8ypgGmqtJdneICBD6qY/MImdq+MeNFq4L8hpz7yH9mRINmjKRUgwRHOB6kAp7ISFi lUlF5SwSLH0dH/oW6XCE/2666//dc8QBMdM8Lihp6ZTQX1IjoS5rjMDGajuWktUAfi HH5xDfUqiGd6A== Message-ID: <682151bebb5125c1f6ee0eac7b931096@kernel.org> From: Tejun Heo To: Andrea Righi Cc: David Vernet , Changwoo Min , John Stultz , Ingo Molnar , Peter Zijlstra , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Valentin Schneider , K Prateek Nayak , Christian Loehle , David Dai , Koba Ko , Aiqun Yu , Shuah Khan , Emil Tsalapatis , sched-ext@lists.linux.dev, linux-kernel@vger.kernel.org Subject: Re: [PATCH 09/12] sched_ext: Delegate proxy donor admission to BPF schedulers Date: Wed, 22 Jul 2026 13:26:03 -1000 In-Reply-To: <20260721063242.552774-10-arighi@nvidia.com> References: <20260721063242.552774-1-arighi@nvidia.com> <20260721063242.552774-10-arighi@nvidia.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Hello, Andrea. On Tue, Jul 21, 2026 at 08:31:30AM +0200, Andrea Righi wrote: > A proxy migration preserves the donor's wake_cpu while moving its > scheduling context to the owner's rq, so task_cpu() differs from wake_cpu > until the donor wakes. Prevent BPF-directed migrations from pulling a > blocked donor off this proxy rq. Otherwise each blocked re-enqueue may > move the donor back to its callback rq only for proxy execution to move > it to the owner again. The description reads scattered - from here on, it's a flat list of corner cases, one per hunk, and the design that connects them never gets stated. > + /* %SCX_OPS_ENQ_BLOCKED takes precedence over the fallbacks below. */ > + enq_blocked = (sch->ops.flags & SCX_OPS_ENQ_BLOCKED) && > + p->is_blocked && !(enq_flags & SCX_ENQ_WAKEUP); > + if (enq_blocked) > + enq_flags |= SCX_ENQ_BLOCKED; > + > /* see %SCX_OPS_ENQ_EXITING */ > - if (!(sch->ops.flags & SCX_OPS_ENQ_EXITING) && > + if (!enq_blocked && !(sch->ops.flags & SCX_OPS_ENQ_EXITING) && > unlikely(p->flags & PF_EXITING)) { > __scx_add_event(sch, SCX_EV_ENQ_SKIP_EXITING, 1); > goto local; > } > > /* see %SCX_OPS_ENQ_MIGRATION_DISABLED */ > - if (!(sch->ops.flags & SCX_OPS_ENQ_MIGRATION_DISABLED) && > + if (!enq_blocked && > + !(sch->ops.flags & SCX_OPS_ENQ_MIGRATION_DISABLED) && > is_migration_disabled(p)) { > __scx_add_event(sch, SCX_EV_ENQ_SKIP_MIGRATION_DISABLED, 1); > goto local; > } Both fallbacks repeating !enq_blocked reads awkward. How about grouping them? if (enq_blocked) { enq_flags |= SCX_ENQ_BLOCKED; } else { /* see %SCX_OPS_ENQ_EXITING */ if (!(sch->ops.flags & SCX_OPS_ENQ_EXITING) && unlikely(p->flags & PF_EXITING)) { ... } /* see %SCX_OPS_ENQ_MIGRATION_DISABLED */ if (!(sch->ops.flags & SCX_OPS_ENQ_MIGRATION_DISABLED) && is_migration_disabled(p)) { ... } } The "takes precedence" comment can then go away as the structure says it. Thanks. -- tejun