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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?

  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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