From: Jann Horn <jannh@google.com>
To: Andrei Vagin <avagin@gmail.com>
Cc: Peter Oskolkov <posk@google.com>,
Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@redhat.com>,
Thomas Gleixner <tglx@linutronix.de>,
kernel list <linux-kernel@vger.kernel.org>,
Linux API <linux-api@vger.kernel.org>,
Paul Turner <pjt@google.com>, Ben Segall <bsegall@google.com>,
Peter Oskolkov <posk@posk.io>,
Joel Fernandes <joel@joelfernandes.org>,
Andrew Morton <akpm@linux-foundation.org>,
Andrei Vagin <avagin@google.com>,
Jim Newsome <jnewsome@torproject.org>
Subject: Re: [RFC PATCH v0.1 4/9] sched/umcg: implement core UMCG API
Date: Fri, 21 May 2021 23:31:52 +0200 [thread overview]
Message-ID: <CAG48ez0=ndXMCM-hST1WLMpQu5X9w_93Df=EoBqdq+DhC_HwbQ@mail.gmail.com> (raw)
In-Reply-To: <YKgEn/TBsTyhk0m1@gmail.com>
On Fri, May 21, 2021 at 9:09 PM Andrei Vagin <avagin@gmail.com> wrote:
> On Thu, May 20, 2021 at 11:36:09AM -0700, Peter Oskolkov wrote:
> > @@ -67,7 +137,75 @@ SYSCALL_DEFINE4(umcg_register_task, u32, api_version, u32, flags, u32, group_id,
> > */
> > SYSCALL_DEFINE1(umcg_unregister_task, u32, flags)
> > {
> > - return -ENOSYS;
> > + struct umcg_task_data *utd;
> > + int ret = -EINVAL;
> > +
> > + rcu_read_lock();
> > + utd = rcu_dereference(current->umcg_task_data);
> > +
> > + if (!utd || flags)
> > + goto out;
> > +
> > + task_lock(current);
> > + rcu_assign_pointer(current->umcg_task_data, NULL);
> > + task_unlock(current);
> > +
> > + ret = 0;
> > +
> > +out:
> > + rcu_read_unlock();
> > + if (!ret && utd) {
> > + synchronize_rcu();
>
> synchronize_rcu is expensive. Do we really need to call it here? Can we
> use kfree_rcu?
>
> Where is task->umcg_task_data freed when a task is destroyed?
or executed - the umcg stuff includes a userspace pointer, so it
probably shouldn't normally be kept around across execve?
next prev parent reply other threads:[~2021-05-21 21:32 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-20 18:36 [RFC PATCH v0.1 0/9] UMCG early preview/RFC patchset Peter Oskolkov
2021-05-20 18:36 ` [RFC PATCH v0.1 1/9] sched/umcg: add UMCG syscall stubs and CONFIG_UMCG Peter Oskolkov
2021-05-20 18:36 ` [RFC PATCH v0.1 2/9] sched/umcg: add uapi/linux/umcg.h and sched/umcg.c Peter Oskolkov
2021-05-20 18:36 ` [RFC PATCH v0.1 3/9] sched: add WF_CURRENT_CPU and externise ttwu Peter Oskolkov
2021-05-20 18:36 ` [RFC PATCH v0.1 4/9] sched/umcg: implement core UMCG API Peter Oskolkov
2021-05-21 19:06 ` Andrei Vagin
2021-05-21 21:31 ` Jann Horn [this message]
2021-05-21 22:03 ` Peter Oskolkov
2021-05-21 19:32 ` Andy Lutomirski
2021-05-21 22:01 ` Peter Oskolkov
2021-05-21 21:33 ` Jann Horn
2021-06-09 13:01 ` Peter Zijlstra
2021-05-20 18:36 ` [RFC PATCH v0.1 5/9] lib/umcg: implement UMCG core API for userspace Peter Oskolkov
2021-05-20 18:36 ` [RFC PATCH v0.1 6/9] selftests/umcg: add UMCG core API selftest Peter Oskolkov
2021-05-20 18:36 ` [RFC PATCH v0.1 7/9] sched/umcg: add UMCG server/worker API (early RFC) Peter Oskolkov
2021-05-21 20:17 ` Andrei Vagin
2021-05-20 18:36 ` [RFC PATCH v0.1 8/9] lib/umcg: " Peter Oskolkov
2021-05-20 18:36 ` [RFC PATCH v0.1 9/9] selftests/umcg: add UMCG server/worker API selftest Peter Oskolkov
2021-05-20 21:17 ` [RFC PATCH v0.1 0/9] UMCG early preview/RFC patchset Jonathan Corbet
2021-05-20 21:38 ` Peter Oskolkov
2021-05-21 0:15 ` Randy Dunlap
2021-05-21 8:04 ` Peter Zijlstra
2021-05-21 15:08 ` Jonathan Corbet
2021-05-21 16:03 ` Peter Oskolkov
2021-05-21 19:17 ` Jonathan Corbet
2021-05-27 0:06 ` Peter Oskolkov
2021-05-27 15:41 ` Jonathan Corbet
[not found] ` <CAEWA0a72SvpcuN4ov=98T3uWtExPCr7BQePOgjkqD1ofWKEASw@mail.gmail.com>
2021-05-21 19:13 ` Peter Oskolkov
2021-05-21 23:08 ` Jann Horn
2021-06-09 12:54 ` Peter Zijlstra
2021-06-09 20:18 ` Peter Oskolkov
2021-06-10 18:02 ` Peter Zijlstra
2021-06-10 20:06 ` Peter Oskolkov
2021-07-07 17:45 ` Thierry Delisle
2021-07-08 21:44 ` Peter Oskolkov
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