From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=95.215.58.160 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1794298731; b=QEd88Ml1yPh5e26g+w51FdBM6atx+tvIZ8VCaFQf3P8Ht/Ozn1Ti7SlWh832kzAG6Oiu XVu+DqYdkUb+Tzk9y15/1rhIHyFkacWGSjWuKrK3mqSz2yYwKR9J5Nf7mgJ+M8vqPGg74 tR/3yDIplh7AW262Ru2EfOlV1VS9eVPSUCz5KCURxWhZAGeOTjEgxy5d7plTBVzu+ooIX flFSgrbL0VKyfXAq1zNyppAd5ybbH9EaF2lfNDHG7uOgVLp1jm+74tpIdKhXAFq80rAAC 6/KyR0BGb1aNXXzdHvyriix/n8gURgZQSKhLxlvClzS56IMdIdj7yGyUqyWPI7lmiEg== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794298731; h=DMARC-Filter:X-Envelope-To:DKIM-Signature:X-Envelope-To:Received: X-Mizu-Trace-ID:X-Migadu-Flow:Message-ID:Date:MIME-Version:User-Agent: Subject:To:Cc:References:Content-Language:From:In-Reply-To: Content-Type:Content-Transfer-Encoding; bh=E1d0Y8AFs/r4KdEu5f8rkTIOQJWTjXuDjQHahzUaRu0=; b=1ShgBswhkLaxSUO3wrEmu1/0iJMRzhkSR9zg/XvyHidmYx9LcjyaonBUXNfOFF4DMmXq D5P6XROBm6g7q3FIk5z0EAQQZnxa7Bx/2RLBZPNcWnlCK7m88petZXXjp1uQnPFaQGejl WhM4USkkc20q3RnG9WIlchx+4nP1V+kQoxBI+94IevE3K9FB2OBeBEsT7ERjY/A5av3Hc uikr5yrTyO6yCEGQpKcjMjXVu7z0JOdRqSN6AOn3mh5jOBonxp0l84G5An2q6Ux5D4Fo9 jDDGeLqjs9623Iq52fQCmln0+WDJjMWyXyxWeLmN8Sf/cifKiv2opW61FQJfv/iZOkg== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass header.d=linux.dev header.i=@linux.dev header.a=rsa-sha256 header.s=key1 header.b=cxnjTVUm; arc=none smtp.remote-ip=95.215.58.160 Received: from mta1.migadu.com (out-160.mta1.migadu.com [95.215.58.160]) (using TLSv1.3 with cipher TLS_AES_128_GCM_SHA256 (128/128 bits) key-exchange X25519 server-signature ECDSA (prime256v1) server-digest SHA256) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id B035860A2601 for ; Tue, 10 Nov 2026 08:18:49 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.2 smtp.subspace.kernel.org B035860A2601 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key, unprotected) header.d=linux.dev header.i=@linux.dev header.a=rsa-sha256 header.s=key1 header.b=cxnjTVUm X-Envelope-To: linux-kernel@vger.kernel.org DKIM-Signature: a=rsa-sha256; bh=h51mbEgDokfWt7y+tgY8pofTmHxOpDVgA/1opxZbMyo=; c=simple/simple; d=linux.dev; h=from:to:subject:date:message-id:mime-version:content-type; s=key1; t=1794298727; v=1; x=1794903527; b=cxnjTVUmdHVcUhvJpuUA+nW3kqxyd4P/9C4F0Jj7hgtBZlifYvd4J2MJE99bI2UW/dWvjTW6 ItqYAv5IxGDuEMrOuNerEHfX+zNgCE2ftkWhfyji9oBfvs1wzBIkcVQt8irfISRCIKHpcg/vsbq dfWRRflVyahj+ERw6RhPfhRw= X-Envelope-To: linux-kernel@vger.kernel.org Received: by smtp.migadu.com with ESMTPS id ea234c83bdd75544; Tue, 10 Nov 2026 08:18:47 +0000 X-Mizu-Trace-ID: ea234c83bdd75544 X-Migadu-Flow: FLOW_OUT Message-ID: <5a141006-e289-45db-a928-c3685eb377e9@linux.dev> Date: Tue, 10 Nov 2026 16:18:39 +0800 X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 3/4] cpuset: settle isolation state when CPUs are given back to parent To: Ridong Chen , Waiman Long , Tejun Heo , Johannes Weiner , =?UTF-8?Q?Michal_Koutn=C3=BD?= , Shuah Khan Cc: Chen Ridong , cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, Sashiko , Guopeng Zhang , Ridong Chen References: <20261107120100.3587595-1-ridong.chen@linux.dev> <20261107120100.3587595-4-ridong.chen@linux.dev> <09c033dd-41dc-4503-9def-4e662e946dc4@redhat.com> Content-Language: en-US From: Guopeng Zhang In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 在 2026/11/10 11:14, Ridong Chen 写道: > > > On 11/9/2026 10:51 PM, Waiman Long wrote: >> On 11/7/26 7:00 AM, Ridong Chen wrote: >>> From: Ridong Chen >>> >>> partition_xcpus_del() only updates isolated_cpus when the partition that >>> gives back the CPUs has a different state than its parent. CPUs that were >>> further distributed to descendant isolated partitions are not taken into >>> account, so isolated_cpus_release() has to be called afterwards in >>> several places to walk up the ancestors and fix isolated_cpus. >>> >>> Make partition_xcpus_del() always set the isolation state of the given >>> back CPUs to the state of the parent that receives them. As the >>> effective_xcpus of a partition covers the CPUs distributed to its >>> descendants, the isolation state of those CPUs is settled at the same >>> time. Boot-time isolated CPUs are still preserved by isolated_cpu_update(). >>> >>> compute_partition_effective_cpumask() invalidates a child partition >>> without going through partition_xcpus_del(), so do the same there: the >>> CPUs of the invalidated child take the isolation state of its parent. >>> >>> As the parent may be shrunk and its effective_xcpus not updated yet, >>> only do so for the CPUs the parent still owns. This is to keep the >>> isolation state correct for now, the in-place invalidation here will be >>> removed later in the partition rework. >>> >>> isolated_cpus_update() assumes the old and new states are different, >>> which no longer holds now that partition_xcpus_del() proceeds regardless >>> of the states. Drop its @old_prs argument and the WARN_ON_ONCE() so that >>> it simply sets the isolation state of the given CPUs, and use it >>> everywhere. The state check in partition_xcpus_add() is dropped as well, >>> as setting the state is a no-op when the states are the same. >>> >>> isolated_cpus_release() is no longer needed and is removed. >>> >>> Signed-off-by: Ridong Chen >>> --- >>>   kernel/cgroup/cpuset.c | 98 ++++++++---------------------------------- >>>   1 file changed, 19 insertions(+), 79 deletions(-) >>> >>> diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c >>> index 85e5b529d144..fc9de6e16ff5 100644 >>> --- a/kernel/cgroup/cpuset.c >>> +++ b/kernel/cgroup/cpuset.c >>> @@ -1244,17 +1244,17 @@ static bool isolated_cpu_update(int new_prs, int cpu) >>>   } >>>   /* >>> - * isolated_cpus_update - Update the isolated_cpus mask >>> - * @old_prs: old partition_root_state >>> - * @new_prs: new partition_root_state >>> - * @xcpus: exclusive CPUs with state change >>> + * isolated_cpus_update - Set the isolation state of @xcpus >>> + * @new_prs: partition root state that @xcpus will belong to >>> + * @xcpus: exclusive CPUs whose isolation state may change >>> + * >>> + * CPUs isolated at boot time are kept isolated. >>>    */ >>> -static void isolated_cpus_update(int old_prs, int new_prs, struct cpumask *xcpus) >>> +static void isolated_cpus_update(int new_prs, struct cpumask *xcpus) >>>   { >>>       bool updated = false; >>>       int cpu; >>> -    WARN_ON_ONCE(old_prs == new_prs); >>>       lockdep_assert_held(&callback_lock); >>>       lockdep_assert_held(&cpuset_mutex); >>>       for_each_cpu(cpu, xcpus) >>> @@ -1263,45 +1263,6 @@ static void isolated_cpus_update(int old_prs, int new_prs, struct cpumask *xcpus >>>           update_housekeeping = true; >>>   } >>> -/* >>> - * isolated_cpus_release - Remove the relevant CPUs in @xcpus from isolated_cpus >>> - * @cs: the current cpuset >>> - * @xcpus: the set of effective xcpus to be considered for removal >>> - * >>> - * This function is called when an isolated partition is invalidated or when >>> - * some of its effective xcpus are to be removed from isolated_cpus due to >>> - * changes in parent cpuset. The given @xcpus must be modifiable as the function >>> - * will update its value to determine the right set of CPUs to be removed. >>> - */ >>> -static void isolated_cpus_release(struct cpuset *cs, struct cpumask *xcpus) >>> -{ >>> -    struct cpuset *ancestor = parent_cs(cs); >>> -    struct cpuset *iancestor = NULL; >>> - >>> -    /* >>> -     * Search the furthest isolated partition root ancestor available >>> -     * until top_cpuset or a remote partition root is hit. >>> -     */ >>> -    for (; ancestor; ancestor = parent_cs(ancestor)) { >>> -        if (ancestor->partition_root_state == PRS_ISOLATED) >>> -            iancestor = ancestor; >>> -        if (is_remote_partition(ancestor)) >>> -            break; >>> -    } >>> - >>> -    /* >>> -     * If a furthest isolated partition acnestor is found, use it to >>> -     * determine which of the CPUs in @xcpus should be removed from >>> -     * isolated_cpus. Otherwise, all of them will be removed. >>> -     */ >>> -    if (iancestor && !cpumask_andnot(xcpus, xcpus, iancestor->effective_xcpus)) >>> -        return; /* No CPU should be removed from isolated_cpus */ >>> - >>> -    spin_lock_irq(&callback_lock); >>> -    isolated_cpus_update(PRS_ISOLATED, PRS_ROOT, xcpus); >>> -    spin_unlock_irq(&callback_lock); >>> -} >>> - >>>   /* >>>    * partition_xcpus_add - Add new exclusive CPUs to partition >>>    * @new_prs: new partition_root_state >>> @@ -1325,9 +1286,7 @@ static void partition_xcpus_add(int new_prs, struct cpuset *parent, >>>       if (parent == &top_cpuset) >>>           cpumask_or(subpartitions_cpus, subpartitions_cpus, xcpus); >>> -    if (new_prs != parent->partition_root_state) >>> -        isolated_cpus_update(parent->partition_root_state, new_prs, >>> -                     xcpus); >>> +    isolated_cpus_update(new_prs, xcpus); >>>       cpumask_andnot(parent->effective_cpus, parent->effective_cpus, xcpus); >>>   } >>> @@ -1355,9 +1314,8 @@ static void partition_xcpus_del(int old_prs, struct cpuset *parent, >>>       if (parent == &top_cpuset) >>>           cpumask_andnot(subpartitions_cpus, subpartitions_cpus, xcpus); >>> -    if (old_prs != parent->partition_root_state) >>> -        isolated_cpus_update(old_prs, parent->partition_root_state, >>> -                     xcpus); >>> +    /* CPUs given back, including those of descendants, take parent's state */ >>> +    isolated_cpus_update(parent->partition_root_state, xcpus); >>>       cpumask_or(parent->effective_cpus, parent->effective_cpus, xcpus); >>>       cpumask_and(parent->effective_cpus, parent->effective_cpus, cpu_active_mask); >>> @@ -1612,6 +1570,7 @@ static void compute_partition_effective_cpumask(struct cpuset *cs, >>>       struct cgroup_subsys_state *css; >>>       struct cpuset *child; >>>       bool populated = partition_is_populated(cs, NULL); >>> +    static cpumask_t xcpus;        /* Protected by cpuset_mutex */ >>>       /* >>>        * Check child partition roots to see if they should be invalidated >>> @@ -1640,14 +1599,15 @@ static void compute_partition_effective_cpumask(struct cpuset *cs, >>>               int parent_prs = cs->partition_root_state; >>>               /* >>> -             * Invalidate child partition and update isolated_cpus >>> -             * if necessary. >>> +             * Invalidate child partition. Its CPUs still owned by >>> +             * cs take the isolation state of cs. effective_xcpus >>> +             * of cs may not be updated yet, so recompute it. >>>                */ >>>               spin_lock_irq(&callback_lock); >>>               WRITE_ONCE(child->prs_err, PERR_NOCPUS); >>> -            if ((old_prs == PRS_ISOLATED) && (parent_prs == PRS_ROOT)) >>> -                isolated_cpus_update(PRS_ISOLATED, PRS_ROOT, >>> -                             child->effective_xcpus); >>> +            compute_excpus(cs, &xcpus); >>> +            cpumask_and(&xcpus, &xcpus, child->effective_xcpus); >>> +            isolated_cpus_update(parent_prs, &xcpus); >>>               child->partition_root_state = -old_prs; >>>               spin_unlock_irq(&callback_lock); >>>               notify_partition_change(child, old_prs); >>> @@ -2080,22 +2040,8 @@ static int update_parent_effective_cpumask(struct cpuset *cs, int cmd, >>>            * >>>            * A partition error happens when parent has tasks and all >>>            * its effective CPUs will have to be distributed out. >>> -         * >>> -         * For an isolated partition with a shrunk root partition parent >>> -         * we may need to return some or all of its isolated CPUs. >>>            */ >>>           nocpu |= cpumask_empty(tmp->delmask); >>> -        if ((parent_prs == PRS_ROOT) && (old_prs == PRS_ISOLATED)) { >>> -            cpumask_clear(tmp->addmask); >>> -            if (nocpu) >>> -                cpumask_copy(tmp->addmask, cs->effective_xcpus); >>> -            else if (!cpumask_subset(cs->effective_xcpus, parent- >effective_xcpus)) >>> -                cpumask_andnot(tmp->addmask, cs->effective_xcpus, >>> -                                 parent->effective_xcpus); >>> -            if (!cpumask_empty(tmp->addmask)) >>> -                isolated_cpus_release(cs, tmp->addmask); >>> -            /* Expansion of parent's effective_xcpus is handled below */ >>> -        } >>>           if (nocpu) { >>>               part_error = PERR_NOCPUS; >>>               if (is_partition_valid(cs)) >>> @@ -2341,18 +2287,12 @@ static void update_cpumasks_hier(struct cpuset *cs, struct tmpmasks *tmp, >>>                   /* >>>                    * When parent is not a valid partition root, >>>                    * child partition roots become invalid too. >>> -                 * >>> -                 * For a to be invalidated isolated partition, >>> -                 * call return_isolated_cpus() to remove the >>> -                 * relevant CPUs from isolated_cpus. >>> +                 * The isolation state of their CPUs has been >>> +                 * settled when the parent gave them back. >>>                    */ >>>                   if (is_partition_valid(cp)) >>>                       new_prs = -old_prs; >>> -                if (old_prs == PRS_ISOLATED) { >>> -                    cpumask_copy(tmp->delmask, cp->effective_xcpus); >>> -                    isolated_cpus_release(cp, tmp->delmask); >>> -                } >>>                   WRITE_ONCE(cp->prs_err, >>>                          is_partition_invalid(parent) >>>                          ? PERR_INVPARENT : PERR_NOTPART); >>> @@ -3108,7 +3048,7 @@ static int update_prstate(struct cpuset *cs, int new_prs) >>>       if (!is_partition_valid(cs)) >>>           reset_partition_data(cs); >>>       else if (isolcpus_updated) >>> -        isolated_cpus_update(old_prs, new_prs, cs->effective_xcpus); >>> +        isolated_cpus_update(new_prs, cs->effective_xcpus); >>>       spin_unlock_irq(&callback_lock); >>>       /* Force update if partition is disabled & update effective_xcpus */ >> >> The code change looks good to me. However this is not just a code restructuring, it also includes a bug fix. I wonder if we should clarify that and maybe add a Fixes tag. >> > Hi Longman, > > Thanks for the review. You are right, it also fixes the isolated CPU > leak reported by Guopeng [1]. When a root partition with an isolated > child partition is invalidated, partition_xcpus_del() gives the CPUs > back to the parent without updating isolated_cpus as both are root > partitions, so the CPUs of the isolated child are left in > isolated_cpus. > > I'd like to describe it in the commit message and add the following > tags in the next version: > > Fixes: 11e5f407b64a ("cgroup/cpuset: Keep track of CPUs in isolated partitions") > Reported-by: Guopeng Zhang > Closes: https://lore.kernel.org/all/20261105130344.664336-4-guopeng.zhang@linux.dev/ > > Does that look OK to you? > > [1] https://lore.kernel.org/all/20261105130344.664336-4-guopeng.zhang@linux.dev/ > Hi Ridong, Since I've dropped my patch, I haven't added the reproducer to the selftests separately. If it's convenient, could you also include it in test_cpuset_prs.sh in v4? Thanks， Guopeng