| lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
|
Open Source and information security mailing list archives
| ||
|
Message-ID: <aNJlk7wcAsPF_j-z@2a01cb069018a810e4ede1071806178f.ipv6.abo.wanadoo.fr>
Date: Tue, 23 Sep 2025 11:17:07 +0200
From: Frederic Weisbecker <frederic@...nel.org>
To: Waiman Long <llong@...hat.com>
Cc: LKML <linux-kernel@...r.kernel.org>,
Gabriele Monaco <gmonaco@...hat.com>,
Johannes Weiner <hannes@...xchg.org>,
Marco Crivellari <marco.crivellari@...e.com>,
Michal Hocko <mhocko@...e.com>,
Michal Koutný <mkoutny@...e.com>,
Peter Zijlstra <peterz@...radead.org>, Tejun Heo <tj@...nel.org>,
Thomas Gleixner <tglx@...utronix.de>, cgroups@...r.kernel.org
Subject: Re: [PATCH 26/33] cgroup/cpuset: Fail if isolated and nohz_full
don't leave any housekeeping
Le Tue, Sep 02, 2025 at 11:44:00AM -0400, Waiman Long a écrit :
>
> On 8/29/25 11:48 AM, Frederic Weisbecker wrote:
> > From: Gabriele Monaco <gmonaco@...hat.com>
> >
> > Currently the user can set up isolated cpus via cpuset and nohz_full in
> > such a way that leaves no housekeeping CPU (i.e. no CPU that is neither
> > domain isolated nor nohz full). This can be a problem for other
> > subsystems (e.g. the timer wheel imgration).
> >
> > Prevent this configuration by blocking any assignation that would cause
> > the union of domain isolated cpus and nohz_full to covers all CPUs.
> >
> > Acked-by: Frederic Weisbecker <frederic@...nel.org>
> > Signed-off-by: Gabriele Monaco <gmonaco@...hat.com>
> > Signed-off-by: Frederic Weisbecker <frederic@...nel.org>
> > ---
> > kernel/cgroup/cpuset.c | 57 ++++++++++++++++++++++++++++++++++++++++++
> > 1 file changed, 57 insertions(+)
> >
> > diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
> > index df1dfacf5f9d..8260dd699fd8 100644
> > --- a/kernel/cgroup/cpuset.c
> > +++ b/kernel/cgroup/cpuset.c
> > @@ -1275,6 +1275,19 @@ static void isolated_cpus_update(int old_prs, int new_prs, struct cpumask *xcpus
> > cpumask_andnot(isolated_cpus, isolated_cpus, xcpus);
> > }
> > +/*
> > + * isolated_cpus_should_update - Returns if the isolated_cpus mask needs update
> > + * @prs: new or old partition_root_state
> > + * @parent: parent cpuset
> > + * Return: true if isolated_cpus needs modification, false otherwise
> > + */
> > +static bool isolated_cpus_should_update(int prs, struct cpuset *parent)
> > +{
> > + if (!parent)
> > + parent = &top_cpuset;
> > + return prs != parent->partition_root_state;
> > +}
> > +
> > /*
> > * partition_xcpus_add - Add new exclusive CPUs to partition
> > * @new_prs: new partition_root_state
> > @@ -1339,6 +1352,36 @@ static bool partition_xcpus_del(int old_prs, struct cpuset *parent,
> > return isolcpus_updated;
> > }
> > +/*
> > + * isolcpus_nohz_conflict - check for isolated & nohz_full conflicts
> > + * @new_cpus: cpu mask for cpus that are going to be isolated
> > + * Return: true if there is conflict, false otherwise
> > + *
> > + * If nohz_full is enabled and we have isolated CPUs, their combination must
> > + * still leave housekeeping CPUs.
> > + */
> > +static bool isolcpus_nohz_conflict(struct cpumask *new_cpus)
> > +{
> > + cpumask_var_t full_hk_cpus;
> > + int res = false;
> > +
> > + if (!housekeeping_enabled(HK_TYPE_KERNEL_NOISE))
> > + return false;
> > +
> > + if (!alloc_cpumask_var(&full_hk_cpus, GFP_KERNEL))
> > + return true;
> > +
> > + cpumask_and(full_hk_cpus, housekeeping_cpumask(HK_TYPE_KERNEL_NOISE),
> > + housekeeping_cpumask(HK_TYPE_DOMAIN));
> > + cpumask_andnot(full_hk_cpus, full_hk_cpus, isolated_cpus);
> > + cpumask_and(full_hk_cpus, full_hk_cpus, cpu_online_mask);
> > + if (!cpumask_weight_andnot(full_hk_cpus, new_cpus))
> > + res = true;
> > +
> > + free_cpumask_var(full_hk_cpus);
> > + return res;
> > +}
> > +
> > static void update_housekeeping_cpumask(bool isolcpus_updated)
> > {
> > int ret;
> > @@ -1453,6 +1496,9 @@ static int remote_partition_enable(struct cpuset *cs, int new_prs,
> > if (!cpumask_intersects(tmp->new_cpus, cpu_active_mask) ||
> > cpumask_subset(top_cpuset.effective_cpus, tmp->new_cpus))
> > return PERR_INVCPUS;
> > + if (isolated_cpus_should_update(new_prs, NULL) &&
> > + isolcpus_nohz_conflict(tmp->new_cpus))
> > + return PERR_HKEEPING;
> > spin_lock_irq(&callback_lock);
> > isolcpus_updated = partition_xcpus_add(new_prs, NULL, tmp->new_cpus);
> > @@ -1552,6 +1598,9 @@ static void remote_cpus_update(struct cpuset *cs, struct cpumask *xcpus,
> > else if (cpumask_intersects(tmp->addmask, subpartitions_cpus) ||
> > cpumask_subset(top_cpuset.effective_cpus, tmp->addmask))
> > cs->prs_err = PERR_NOCPUS;
> > + else if (isolated_cpus_should_update(prs, NULL) &&
> > + isolcpus_nohz_conflict(tmp->addmask))
> > + cs->prs_err = PERR_HKEEPING;
> > if (cs->prs_err)
> > goto invalidate;
> > }
> > @@ -1904,6 +1953,12 @@ static int update_parent_effective_cpumask(struct cpuset *cs, int cmd,
> > return err;
> > }
> > + if (deleting && isolated_cpus_should_update(new_prs, parent) &&
> > + isolcpus_nohz_conflict(tmp->delmask)) {
> > + cs->prs_err = PERR_HKEEPING;
> > + return PERR_HKEEPING;
> > + }
> > +
> > /*
> > * Change the parent's effective_cpus & effective_xcpus (top cpuset
> > * only).
> > @@ -2924,6 +2979,8 @@ static int update_prstate(struct cpuset *cs, int new_prs)
> > * Need to update isolated_cpus.
> > */
> > isolcpus_updated = true;
> > + if (isolcpus_nohz_conflict(cs->effective_xcpus))
> > + err = PERR_HKEEPING;
> > } else {
> > /*
> > * Switching back to member is always allowed even if it
>
> In both remote_cpus_update() and update_parent_effective_cpumask(), some new
> CPUs can be added to the isolation list while other CPUs can be removed from
> it. So isolcpus_nohz_conflict() should include both set in its analysis to
> avoid false positive. Essentally, if the CPUs removed from the isolated_cpus
> intersect with the nohz_full housekeeping mask, there is no conflict.
I assume this was fixed in latest Gabriele posting?
Thanks.
>
> Cheers,
> Longman
>
--
Frederic Weisbecker
SUSE Labs
Powered by blists - more mailing lists