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([2601:600:947f:f020:85dc:d2b2:c5ee:e3c4]) by smtp.gmail.com with ESMTPSA id 6a1803df08f44-87d028af525sm62600596d6.51.2025.10.20.21.10.17 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 20 Oct 2025 21:10:20 -0700 (PDT) From: Waiman Long X-Google-Original-From: Waiman Long Message-ID: <0e02915f-bde7-4b04-b760-89f34fb0a436@redhat.com> Date: Tue, 21 Oct 2025 00:10:16 -0400 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 13/33] cpuset: Update HK_TYPE_DOMAIN cpumask from cpuset To: Frederic Weisbecker , LKML Cc: =?UTF-8?Q?Michal_Koutn=C3=BD?= , Andrew Morton , Bjorn Helgaas , Catalin Marinas , Danilo Krummrich , "David S . Miller" , Eric Dumazet , Gabriele Monaco , Greg Kroah-Hartman , Ingo Molnar , Jakub Kicinski , Jens Axboe , Johannes Weiner , Lai Jiangshan , Marco Crivellari , Michal Hocko , Muchun Song , Paolo Abeni , Peter Zijlstra , Phil Auld , "Rafael J . Wysocki" , Roman Gushchin , Shakeel Butt , Simon Horman , Tejun Heo , Thomas Gleixner , Vlastimil Babka , Will Deacon , cgroups@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-block@vger.kernel.org, linux-mm@kvack.org, linux-pci@vger.kernel.org, netdev@vger.kernel.org References: <20251013203146.10162-1-frederic@kernel.org> <20251013203146.10162-14-frederic@kernel.org> Content-Language: en-US In-Reply-To: <20251013203146.10162-14-frederic@kernel.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 10/13/25 4:31 PM, Frederic Weisbecker wrote: > Until now, HK_TYPE_DOMAIN used to only include boot defined isolated > CPUs passed through isolcpus= boot option. Users interested in also > knowing the runtime defined isolated CPUs through cpuset must use > different APIs: cpuset_cpu_is_isolated(), cpu_is_isolated(), etc... > > There are many drawbacks to that approach: > > 1) Most interested subsystems want to know about all isolated CPUs, not > just those defined on boot time. > > 2) cpuset_cpu_is_isolated() / cpu_is_isolated() are not synchronized with > concurrent cpuset changes. > > 3) Further cpuset modifications are not propagated to subsystems > > Solve 1) and 2) and centralize all isolated CPUs within the > HK_TYPE_DOMAIN housekeeping cpumask. > > Subsystems can rely on RCU to synchronize against concurrent changes. > > The propagation mentioned in 3) will be handled in further patches. > > Signed-off-by: Frederic Weisbecker > --- > include/linux/sched/isolation.h | 2 + > kernel/cgroup/cpuset.c | 2 + > kernel/sched/isolation.c | 75 ++++++++++++++++++++++++++++++--- > kernel/sched/sched.h | 1 + > 4 files changed, 74 insertions(+), 6 deletions(-) > > diff --git a/include/linux/sched/isolation.h b/include/linux/sched/isolation.h > index da22b038942a..94d5c835121b 100644 > --- a/include/linux/sched/isolation.h > +++ b/include/linux/sched/isolation.h > @@ -32,6 +32,7 @@ extern const struct cpumask *housekeeping_cpumask(enum hk_type type); > extern bool housekeeping_enabled(enum hk_type type); > extern void housekeeping_affine(struct task_struct *t, enum hk_type type); > extern bool housekeeping_test_cpu(int cpu, enum hk_type type); > +extern int housekeeping_update(struct cpumask *mask, enum hk_type type); > extern void __init housekeeping_init(void); > > #else > @@ -59,6 +60,7 @@ static inline bool housekeeping_test_cpu(int cpu, enum hk_type type) > return true; > } > > +static inline int housekeeping_update(struct cpumask *mask, enum hk_type type) { return 0; } > static inline void housekeeping_init(void) { } > #endif /* CONFIG_CPU_ISOLATION */ > > diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c > index aa1ac7bcf2ea..b04a4242f2fa 100644 > --- a/kernel/cgroup/cpuset.c > +++ b/kernel/cgroup/cpuset.c > @@ -1403,6 +1403,8 @@ static void update_unbound_workqueue_cpumask(bool isolcpus_updated) > > ret = workqueue_unbound_exclude_cpumask(isolated_cpus); > WARN_ON_ONCE(ret < 0); > + ret = housekeeping_update(isolated_cpus, HK_TYPE_DOMAIN); > + WARN_ON_ONCE(ret < 0); > } > > /** > diff --git a/kernel/sched/isolation.c b/kernel/sched/isolation.c > index b46c20b5437f..95d69c2102f6 100644 > --- a/kernel/sched/isolation.c > +++ b/kernel/sched/isolation.c > @@ -29,18 +29,48 @@ static struct housekeeping housekeeping; > > bool housekeeping_enabled(enum hk_type type) > { > - return !!(housekeeping.flags & BIT(type)); > + return !!(READ_ONCE(housekeeping.flags) & BIT(type)); > } > EXPORT_SYMBOL_GPL(housekeeping_enabled); > > +static bool housekeeping_dereference_check(enum hk_type type) > +{ > + if (IS_ENABLED(CONFIG_LOCKDEP) && type == HK_TYPE_DOMAIN) { > + /* Cpuset isn't even writable yet? */ > + if (system_state <= SYSTEM_SCHEDULING) > + return true; > + > + /* CPU hotplug write locked, so cpuset partition can't be overwritten */ > + if (IS_ENABLED(CONFIG_HOTPLUG_CPU) && lockdep_is_cpus_write_held()) > + return true; > + > + /* Cpuset lock held, partitions not writable */ > + if (IS_ENABLED(CONFIG_CPUSETS) && lockdep_is_cpuset_held()) > + return true; I have some doubt about this condition as the cpuset_mutex may be held in the process of making changes to an isolated partition that will impact HK_TYPE_DOMAIN cpumask. Cheers, Longman