From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=91.218.175.60 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1794292617; b=44MRl9r9lr2hwTuQnRWZhjCnSQwKFZtuo4U1DLSpUy+h0ZpbJN9lX3MwP/g0OnlwK2/L Dx+PsxnVacFy3OehA6SxV4AvlAVla49nTZwQt4RLgSnRWrgpir0zcWyGKyPl5wW8+n9k1 KyDP02Wu+cNkcUe45bDylfFvsnqE8NnGVheWCQ8qw4SsweUDibxF6gFWhLcQJz0kLJaoK WGsQ9QVRNvbMGCTGBZ7y56/S6rUeHqEVQVuz6Ajb2OGjM6miCAGPoVfHM3Hx8CGuvPdbU +F1SvEHrjeUWgjTcB4ga0PdaQ0N40cOESXrRY46sD0XsC7PY6fZ9C9JNwK5Yz/yrDhA== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794292617; 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:From:In-Reply-To:Content-Type: Content-Transfer-Encoding; bh=xI/Mw+wKpfQ51uGssBou6KQdHiosm5ZcBFVWJhhdHVI=; b=YNATTDtKEoxlYHN7Hl2uCcurH+kq5s/c5Ji8yHgyuRF9WGq4g5T3r0LUiU905vorA1O3 EkcSFOgWS4AnZkkypF/q6WRJQTEcQxcQ2Qa3xkksn3twOZopy+gcWfcZLySWts3FgHV/D 5wybupJYSRt/DBPw5acQbFE8y2x41PbejE9tA/ZU+LKQsCR+eQOKVC/QK9jmIKQXCL5b9 JyanYA13TCQG8PGURCPmYQnIDAOqaHSzyFBFOYK7+H1/TFrryC1aWTbmL1seygJxRNb7F hieJhk6FCJo9hWNWomle/uu0rCOvdypPxKtXzk+tigBKbkLXFbWdY/J8gN1Rzs/puqw== 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=QC5AJa20; arc=none smtp.remote-ip=91.218.175.60 Received: from mta0.migadu.com (out-60.mta0.migadu.com [91.218.175.60]) (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 AF46B606A31C for ; Tue, 10 Nov 2026 06:36:55 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.2 smtp.subspace.kernel.org AF46B606A31C 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=QC5AJa20 X-Envelope-To: linux-kernel@vger.kernel.org DKIM-Signature: a=rsa-sha256; bh=4ldduMkRN9py7oBtMZAvrIPqG9pOjDa0Ze0haB4M5iI=; c=simple/simple; d=linux.dev; h=from:to:subject:date:message-id:mime-version:content-type; s=key1; t=1794292612; v=1; x=1794897412; b=QC5AJa20qTBqMHA6N/5j4zajfrAS+T+P6qUzg3wdvV3PY2DvqAV9Zdsm7NrLaTqwYQlc2ldF 0JhGfsbEIN/Fw7zMA31SDxblcbv62sGdQYEK3wEjuGfjU+OZ3mw9G995UsbGaajIqXl7y4Mf4OH KKkcKMLpO/bGvCByUgF2Bu8U= X-Envelope-To: linux-kernel@vger.kernel.org Received: by smtp.migadu.com with ESMTPS id 88cdc0a77461dabf; Tue, 10 Nov 2026 06:36:52 +0000 X-Mizu-Trace-ID: 88cdc0a77461dabf X-Migadu-Flow: FLOW_OUT Message-ID: Date: Tue, 10 Nov 2026 14:36:47 +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 4/4] cpuset: generalize the validate_partition() interface To: 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> <20261107120100.3587595-5-ridong.chen@linux.dev> From: Ridong Chen In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 11/9/2026 10:52 PM, Waiman Long wrote: > On 11/7/26 7:01 AM, Ridong Chen wrote: >> From: Chen Ridong >> >> Refactor validate_partition() to take the parent partition, the new >> partition root state, the new effective exclusive CPUs and the CPUs to >> be deleted, instead of a trial cpuset. A NULL parent stands for a >> remote partition, whose CPUs come from top_cpuset. This makes the >> interface flexible enough to handle both local and remote partition >> validation. >> >> The no CPU left for tasks check now uses the given parent instead of >> parent_cs(cs), and top_cpuset for a remote partition, as that is where >> its CPUs are taken from. The cgroup parent of a remote partition does >> not give it any CPU. >> >> The housekeeping conflict check is folded into validate_partition(). It >> is skipped when the parent is not a valid partition root, as @cs can't >> be a valid local partition in that case. >> >> Use the new interface for local partition enablement in >> update_parent_effective_cpumask() and in partition_cpus_change(), >> replacing the open-coded checks there. The order of the checks is now >> the same for both paths: empty CPUs, housekeeping conflict, then no CPU >> left for tasks. >> >> Signed-off-by: Chen Ridong >> Signed-off-by: Ridong Chen >> --- >>   kernel/cgroup/cpuset.c | 119 ++++++++++++++++++++--------------------- >>   1 file changed, 59 insertions(+), 60 deletions(-) >> >> diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c >> index fc9de6e16ff5..0ec20412b3ce 100644 >> --- a/kernel/cgroup/cpuset.c >> +++ b/kernel/cgroup/cpuset.c >> @@ -1414,6 +1414,48 @@ static bool prstate_housekeeping_conflict(int new_prs, >> int parent_prs, >>       return res; >>   } >> +/** >> + * validate_partition - Validate a cpuset partition configuration >> + * @cs: The cpuset to validate >> + * @parent: Parent partition of @cs, NULL for remote partition >> + * @new_prs: The proposed new partition root state >> + * @new_excpus: The new effective exclusive CPUs mask to validate >> + * @del: exclusive CPUs to be deleted from @cs, can be NULL >> + * >> + * A remote partition gets its CPUs from top_cpuset, so top_cpuset is used >> + * as the parent when @parent is NULL. >> + * >> + * The housekeeping check is skipped if @parent is not a valid partition >> + * root as @cs can't be a valid local partition in that case. >> + * >> + * Return: PRS error code (0 if valid, non-zero error code if invalid) >> + */ >> +static enum prs_errcode validate_partition(struct cpuset *cs, >> +                       struct cpuset *parent, int new_prs, >> +                       struct cpumask *new_excpus, >> +                       struct cpumask *del) >> +{ >> +    int parent_prs; >> + >> +    if (new_prs == PRS_MEMBER) >> +        return PERR_NONE; >> + >> +    if (cpumask_empty(new_excpus)) >> +        return PERR_INVCPUS; >> + >> +    if (!parent) >> +        parent = &top_cpuset; >> +    parent_prs = parent->partition_root_state; >> +    if (parent_prs > 0 && >> +        prstate_housekeeping_conflict(new_prs, parent_prs, new_excpus, del)) >> +        return PERR_HKEEPING; >> + >> +    if (tasks_nocpu_error(parent, cs, new_excpus)) >> +        return PERR_NOCPUS; >> + >> +    return PERR_NONE; >> +} >> + >>   /* >>    * cpuset_update_sd_hk_unlock - Rebuild sched domains, update HK & unlock >>    * >> @@ -1934,18 +1976,10 @@ static int update_parent_effective_cpumask(struct >> cpuset *cs, int cmd, >>       if ((cmd == partcmd_enable) || (cmd == partcmd_enablei)) { >>           new_prs = (cmd == partcmd_enable) ? PRS_ROOT : PRS_ISOLATED; >> -        /* >> -         * Enabling partition root is not allowed if its >> -         * effective_xcpus is empty. >> -         */ >> -        if (cpumask_empty(tmp->delmask)) >> -            return PERR_INVCPUS; >> - >> -        if (prstate_housekeeping_conflict(new_prs, parent_prs, tmp->delmask, >> NULL)) >> -            return PERR_HKEEPING; >> - >> -        if (nocpu) >> -            return PERR_NOCPUS; >> +        part_error = validate_partition(cs, parent, new_prs, >> +                        tmp->delmask, NULL); >> +        if (part_error) >> +            return part_error; >>           /* >>            * This function will only be called when all the preliminary >> @@ -2424,32 +2458,6 @@ static int parse_cpuset_cpulist(const char *buf, struct >> cpumask *out_mask) >>       return 0; >>   } >> -/** >> - * validate_partition - Validate a cpuset partition configuration >> - * @cs: The cpuset to validate >> - * @trialcs: The trial cpuset containing proposed configuration changes >> - * >> - * If any validation check fails, the appropriate error code is set in the >> - * cpuset's prs_err field. >> - * >> - * Return: PRS error code (0 if valid, non-zero error code if invalid) >> - */ >> -static enum prs_errcode validate_partition(struct cpuset *cs, struct cpuset >> *trialcs) >> -{ >> -    struct cpuset *parent = parent_cs(cs); >> - >> -    if (cs_is_member(trialcs)) >> -        return PERR_NONE; >> - >> -    if (cpumask_empty(trialcs->effective_xcpus)) >> -        return PERR_INVCPUS; >> - >> -    if (tasks_nocpu_error(parent, cs, trialcs->effective_xcpus)) >> -        return PERR_NOCPUS; >> - >> -    return PERR_NONE; >> -} >> - >>   /** >>    * partition_cpus_change - Handle partition state changes due to CPU mask >> updates >>    * @cs: The target cpuset being modified >> @@ -2463,33 +2471,24 @@ static void partition_cpus_change(struct cpuset *cs, >> struct cpuset *trialcs, >>                     struct tmpmasks *tmp) >>   { >>       enum prs_errcode prs_err; >> -    int parent_prs = is_remote_partition(cs) >> -               ? PRS_ROOT : parent_cs(cs)->partition_root_state; >> +    struct cpuset *parent = is_remote_partition(cs) ? NULL : parent_cs(cs); >>       if (cs_is_member(cs)) >>           return; >> -    prs_err = validate_partition(cs, trialcs); >> -    if (!prs_err && (parent_prs > 0) && >> -        !cpumask_empty(trialcs->effective_xcpus)) { >> -        int prs = cs->partition_root_state; >> - >> -        /* >> -         * Check for housekeeping conflict by passing the whole >> -         * effective_xcpus as well as those CPUs that are to be >> -         * removed from cs as delmask. >> -         */ >> -        if (prs > 0) >> -            cpumask_andnot(tmp->delmask, cs->effective_xcpus, >> -                       trialcs->effective_xcpus); >> -        else >> -            cpumask_clear(tmp->delmask); >> - >> -        if (prstate_housekeeping_conflict(prs, parent_prs, >> -                          trialcs->effective_xcpus, tmp->delmask)) >> -            prs_err = PERR_HKEEPING; >> -    } >> +    /* >> +     * Check for housekeeping conflict by passing the whole >> +     * effective_xcpus as well as those CPUs that are to be >> +     * removed from cs as delmask. >> +     */ >> +    if (is_partition_valid(cs)) >> +        cpumask_andnot(tmp->delmask, cs->effective_xcpus, >> +                   trialcs->effective_xcpus); >> +    else >> +        cpumask_clear(tmp->delmask); >> +    prs_err = validate_partition(cs, parent, trialcs->partition_root_state, >> +                     trialcs->effective_xcpus, tmp->delmask); >>       if (prs_err) { >>           WRITE_ONCE(cs->prs_err, prs_err); >>           trialcs->prs_err = prs_err; > > Again, this code change looks good to me. Similar to previous patch, it includes > both code restructuring and bug fixes. > Hi Longman, Thanks for the review. Yes, besides the restructuring, it fixes a false PERR_NOCPUS error for remote partitions. The no CPU left for tasks check in partition_cpus_change() is done against the cgroup parent, but the CPUs of a remote partition come from top_cpuset, not from its parent. It can be reproduced on a 4-CPU system: cd /sys/fs/cgroup echo +cpuset > cgroup.subtree_control mkdir P echo 2-3 > P/cpuset.cpus echo 2-3 > P/cpuset.cpus.exclusive echo +cpuset > P/cgroup.subtree_control mkdir P/C echo 2-3 > P/C/cpuset.cpus echo 2 > P/C/cpuset.cpus.exclusive echo root > P/C/cpuset.cpus.partition sleep 1000 & echo $! > P/cgroup.procs echo 2-3 > P/C/cpuset.cpus.exclusive cat P/C/cpuset.cpus.partition root invalid (Parent is not a partition root) The effective_cpus of P is 3, a subset of the new exclusive CPUs 2-3 of C, and P has a task, so the expansion is rejected. However, P is not a partition root and does not give any CPU to C, and top_cpuset still has CPUs 0-1 for the task. Enabling C directly with exclusive CPUs 2-3 succeeds, as remote_partition_enable() checks top_cpuset instead. With this patch, the expansion succeeds too: cat P/C/cpuset.cpus.partition root The issue has been there since remote partitions were introduced. I reproduced it on commit 181c8e091aae as well, so I'd like to describe it in the commit message and add Fixes: 181c8e091aae ("cgroup/cpuset: Introduce remote partition") in the next version. Does that look OK to you? Please let me know if you are referring to something else. -- Best regards Ridong