From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) (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 3A76676025 for ; Mon, 28 Jul 2025 13:21:40 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.133.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1753708903; cv=none; b=UUucbQVhz2NYRMpLmOrWHZFi2HU5f3C2Lys31hUTsrIwy7FaEm48INHzJPOpK7Qmdy/M+G3D3AZf8F/5bCWrd7uAEl9GvIxJ7p8ndWwpOalY9DCEwNGA23xmoIe3wAxMza/nV4PtYoccLYLyvAQeIquKfywTPOq5AtgK9c4t0uw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1753708903; c=relaxed/simple; bh=Z5K7LoM3PLBfN43u3ceVJLJHJwkol93Ka++ZjqIVAlw=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=qwEUVjFU9gwQ1ytf/XYrc/EpXvBG+itcH8cefXN3vQT69+esehcukLymyR1GGfe98rFJ1gsvchpwGKWprCmbtWSaqEiJTxiYEpFzcgjyQJbgBLBR3sbftZvh68o6LRktf9055tLy79Np+1dz19HRUzTHE9M1We6ZG9IPP4j6xCQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=IjSpe84k; arc=none smtp.client-ip=170.10.133.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="IjSpe84k" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1753708899; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=37h+OxwY37dFS0xXBKuzWk99em7YV/V2JORPqp4C/mM=; b=IjSpe84kPXTkncCvk7z4YaeUtevJQ14BQz+M0yTG5CSmIVia122zV2RT1a5qDi90tNtIbb 3IZWXmGp8XMK0JuUNoBRanoNKBEt1xvOSyExypyENd8FWJgDU4zwABRFS9XT9ShJ4sly2v iAc/WLbeeRAv5YmyDsFlBXs2+7ft754= Received: from mx-prod-mc-02.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-22-gmqrjnTOMLeTOFo9Av4cxA-1; Mon, 28 Jul 2025 09:21:36 -0400 X-MC-Unique: gmqrjnTOMLeTOFo9Av4cxA-1 X-Mimecast-MFC-AGG-ID: gmqrjnTOMLeTOFo9Av4cxA_1753708895 Received: from mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.111]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-02.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 3AB7319560B2; Mon, 28 Jul 2025 13:21:35 +0000 (UTC) Received: from pauld.westford.csb (unknown [10.22.88.177]) by mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 57BD61800B6A; Mon, 28 Jul 2025 13:21:33 +0000 (UTC) Date: Mon, 28 Jul 2025 09:21:29 -0400 From: Phil Auld To: linux-kernel@vger.kernel.org Cc: John Stultz , "Peter Zijlstra (Intel)" , K Prateek Nayak Subject: Re: [tip: sched/core] sched: Add CONFIG_SCHED_PROXY_EXEC & boot argument to enable/disable Message-ID: <20250728132129.GC11434@pauld.westford.csb> References: <20250712033407.2383110-2-jstultz@google.com> <175266115435.406.15916021190678492115.tip-bot2@tip-bot2> 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: <175266115435.406.15916021190678492115.tip-bot2@tip-bot2> X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.111 On Wed, Jul 16, 2025 at 10:19:14AM -0000 tip-bot2 for John Stultz wrote: > The following commit has been merged into the sched/core branch of tip: > Cool! Good work John. "That was easy" ;) Cheers, Phil > Commit-ID: 25c411fce735dda29de26f58d3fce52d4824380c > Gitweb: https://git.kernel.org/tip/25c411fce735dda29de26f58d3fce52d4824380c > Author: John Stultz > AuthorDate: Sat, 12 Jul 2025 03:33:42 > Committer: Peter Zijlstra > CommitterDate: Mon, 14 Jul 2025 17:16:31 +02:00 > > sched: Add CONFIG_SCHED_PROXY_EXEC & boot argument to enable/disable > > Add a CONFIG_SCHED_PROXY_EXEC option, along with a boot argument > sched_proxy_exec= that can be used to disable the feature at boot > time if CONFIG_SCHED_PROXY_EXEC was enabled. > > Also uses this option to allow the rq->donor to be different from > rq->curr. > > Signed-off-by: John Stultz > Signed-off-by: Peter Zijlstra (Intel) > Tested-by: K Prateek Nayak > Link: https://lkml.kernel.org/r/20250712033407.2383110-2-jstultz@google.com > --- > Documentation/admin-guide/kernel-parameters.txt | 5 +++- > include/linux/sched.h | 13 +++++++- > init/Kconfig | 12 +++++++- > kernel/sched/core.c | 29 ++++++++++++++++- > kernel/sched/sched.h | 12 +++++++- > 5 files changed, 71 insertions(+) > > diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt > index 07e22ba..00b8357 100644 > --- a/Documentation/admin-guide/kernel-parameters.txt > +++ b/Documentation/admin-guide/kernel-parameters.txt > @@ -6387,6 +6387,11 @@ > sa1100ir [NET] > See drivers/net/irda/sa1100_ir.c. > > + sched_proxy_exec= [KNL] > + Enables or disables "proxy execution" style > + solution to mutex-based priority inversion. > + Format: > + > sched_verbose [KNL,EARLY] Enables verbose scheduler debug messages. > > schedstats= [KNL,X86] Enable or disable scheduled statistics. > diff --git a/include/linux/sched.h b/include/linux/sched.h > index 54a9126..f225b6b 100644 > --- a/include/linux/sched.h > +++ b/include/linux/sched.h > @@ -1656,6 +1656,19 @@ struct task_struct { > randomized_struct_fields_end > } __attribute__ ((aligned (64))); > > +#ifdef CONFIG_SCHED_PROXY_EXEC > +DECLARE_STATIC_KEY_TRUE(__sched_proxy_exec); > +static inline bool sched_proxy_exec(void) > +{ > + return static_branch_likely(&__sched_proxy_exec); > +} > +#else > +static inline bool sched_proxy_exec(void) > +{ > + return false; > +} > +#endif > + > #define TASK_REPORT_IDLE (TASK_REPORT + 1) > #define TASK_REPORT_MAX (TASK_REPORT_IDLE << 1) > > diff --git a/init/Kconfig b/init/Kconfig > index 965699c..24dd42d 100644 > --- a/init/Kconfig > +++ b/init/Kconfig > @@ -878,6 +878,18 @@ config UCLAMP_BUCKETS_COUNT > > If in doubt, use the default value. > > +config SCHED_PROXY_EXEC > + bool "Proxy Execution" > + # Avoid some build failures w/ PREEMPT_RT until it can be fixed > + depends on !PREEMPT_RT > + # Need to investigate how to inform sched_ext of split contexts > + depends on !SCHED_CLASS_EXT > + # Not particularly useful until we get to multi-rq proxying > + depends on EXPERT > + help > + This option enables proxy execution, a mechanism for mutex-owning > + tasks to inherit the scheduling context of higher priority waiters. > + > endmenu > > # > diff --git a/kernel/sched/core.c b/kernel/sched/core.c > index e9c8bda..dd9f5c0 100644 > --- a/kernel/sched/core.c > +++ b/kernel/sched/core.c > @@ -119,6 +119,35 @@ EXPORT_TRACEPOINT_SYMBOL_GPL(sched_compute_energy_tp); > > DEFINE_PER_CPU_SHARED_ALIGNED(struct rq, runqueues); > > +#ifdef CONFIG_SCHED_PROXY_EXEC > +DEFINE_STATIC_KEY_TRUE(__sched_proxy_exec); > +static int __init setup_proxy_exec(char *str) > +{ > + bool proxy_enable = true; > + > + if (*str && kstrtobool(str + 1, &proxy_enable)) { > + pr_warn("Unable to parse sched_proxy_exec=\n"); > + return 0; > + } > + > + if (proxy_enable) { > + pr_info("sched_proxy_exec enabled via boot arg\n"); > + static_branch_enable(&__sched_proxy_exec); > + } else { > + pr_info("sched_proxy_exec disabled via boot arg\n"); > + static_branch_disable(&__sched_proxy_exec); > + } > + return 1; > +} > +#else > +static int __init setup_proxy_exec(char *str) > +{ > + pr_warn("CONFIG_SCHED_PROXY_EXEC=n, so it cannot be enabled or disabled at boot time\n"); > + return 0; > +} > +#endif > +__setup("sched_proxy_exec", setup_proxy_exec); > + > /* > * Debugging: various feature bits > * > diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h > index ac953fa..e53d0b8 100644 > --- a/kernel/sched/sched.h > +++ b/kernel/sched/sched.h > @@ -1142,10 +1142,15 @@ struct rq { > */ > unsigned long nr_uninterruptible; > > +#ifdef CONFIG_SCHED_PROXY_EXEC > + struct task_struct __rcu *donor; /* Scheduling context */ > + struct task_struct __rcu *curr; /* Execution context */ > +#else > union { > struct task_struct __rcu *donor; /* Scheduler context */ > struct task_struct __rcu *curr; /* Execution context */ > }; > +#endif > struct sched_dl_entity *dl_server; > struct task_struct *idle; > struct task_struct *stop; > @@ -1326,10 +1331,17 @@ DECLARE_PER_CPU_SHARED_ALIGNED(struct rq, runqueues); > #define cpu_curr(cpu) (cpu_rq(cpu)->curr) > #define raw_rq() raw_cpu_ptr(&runqueues) > > +#ifdef CONFIG_SCHED_PROXY_EXEC > +static inline void rq_set_donor(struct rq *rq, struct task_struct *t) > +{ > + rcu_assign_pointer(rq->donor, t); > +} > +#else > static inline void rq_set_donor(struct rq *rq, struct task_struct *t) > { > /* Do nothing */ > } > +#endif > > #ifdef CONFIG_SCHED_CORE > static inline struct cpumask *sched_group_span(struct sched_group *sg); > --