From: Tao Zhou <tao.zhou@linux.dev>
To: Peter Zijlstra <peterz@infradead.org>
Cc: mingo@redhat.com, tglx@linutronix.de, juri.lelli@redhat.com,
vincent.guittot@linaro.org, dietmar.eggemann@arm.com,
rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de,
bristot@redhat.com, linux-kernel@vger.kernel.org,
linux-mm@kvack.org, linux-api@vger.kernel.org, x86@kernel.org,
pjt@google.com, posk@google.com, avagin@google.com,
jannh@google.com, tdelisle@uwaterloo.ca, mark.rutland@arm.com,
posk@posk.io, Tao Zhou <tao.zhou@linux.dev>
Subject: Re: [RFC][PATCH v2 5/5] sched: User Mode Concurency Groups
Date: Fri, 28 Jan 2022 02:47:08 +0800 [thread overview]
Message-ID: <YfLorAvvQJO5uhL5@geo.homenetwork> (raw)
In-Reply-To: <YfKPQJ+Nr4Qokgim@hirez.programming.kicks-ass.net>
On Thu, Jan 27, 2022 at 01:25:36PM +0100, Peter Zijlstra wrote:
> On Mon, Jan 24, 2022 at 10:46:17PM +0800, Tao Zhou wrote:
>
> > > +/* Called from syscall exit path and exceptions that can schedule */
> > > +void umcg_sys_exit(struct pt_regs *regs)
> > > +{
> > > + struct task_struct *tsk = current;
> > > + long syscall = syscall_get_nr(tsk, regs);
> > > +
> > > + if (syscall == __NR_umcg_wait ||
> > > + syscall == __NR_umcg_ctl)
> > > + return;
> > > +
> > > + if (tsk->umcg_server) {
> > > + /*
> > > + * Didn't block, we done.
> > > + */
> > > + umcg_unpin_pages();
> > > + return;
> > > + }
> > > +
> > > + umcg_unblock_and_wait();
> >
> > umcg_unblock_and_wait() -> umcg_enqueue_and_wake() ->
> > umcg_wake_server() -> umcg_wake_task(tsk->umcg_server, ...)
> >
> > tsk->umcg_server is NULL here and umcg_wake_task() use it to update
> > state in umcg_update_state(NULL, ...), that means tsk->umcg_clock
> > will happen something i do not know.
>
> I think umcg_unblock_and_wait() will repin, at which point we should
> have tsk->umcg_server again.
That's right, I miss that.
> > There are two places to call umcg_unblock_and_wait(). One is in
> > umcg_register() where the server is set. Another one is in
> > umcg_sys_exit() where the server is not set. May use a bool to
> > indicate if the server is set.
>
> I'm not sure what you're on about, but I absolutely hate redundant
> state, that only leads to problems.
But, it's my noise though.
next prev parent reply other threads:[~2022-01-27 18:47 UTC|newest]
Thread overview: 47+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-01-20 15:55 [RFC][PATCH v2 0/5] sched: User Managed Concurrency Groups Peter Zijlstra
2022-01-20 15:55 ` [RFC][PATCH v2 1/5] mm: Avoid unmapping pinned pages Peter Zijlstra
2022-01-20 18:03 ` Nadav Amit
2022-01-21 7:59 ` Peter Zijlstra
2022-01-20 18:25 ` David Hildenbrand
2022-01-21 7:51 ` Peter Zijlstra
2022-01-21 8:22 ` David Hildenbrand
2022-01-21 8:59 ` Peter Zijlstra
2022-01-21 9:04 ` David Hildenbrand
2022-01-21 11:40 ` Peter Zijlstra
2022-01-21 12:04 ` David Hildenbrand
2022-01-20 15:55 ` [RFC][PATCH v2 2/5] entry,x86: Create common IRQ operations for exceptions Peter Zijlstra
2022-01-21 16:34 ` Mark Rutland
2022-01-20 15:55 ` [RFC][PATCH v2 3/5] sched/umcg: add WF_CURRENT_CPU and externise ttwu Peter Zijlstra
2022-01-20 15:55 ` [RFC][PATCH v2 4/5] x86/uaccess: Implement unsafe_try_cmpxchg_user() Peter Zijlstra
2022-01-27 2:17 ` Sean Christopherson
2022-01-27 6:36 ` Sean Christopherson
2022-01-27 9:56 ` Peter Zijlstra
2022-01-27 23:33 ` Sean Christopherson
2022-01-28 0:17 ` Nick Desaulniers
2022-01-28 16:29 ` Sean Christopherson
2022-01-27 9:55 ` Peter Zijlstra
2022-01-20 15:55 ` [RFC][PATCH v2 5/5] sched: User Mode Concurency Groups Peter Zijlstra
2022-01-21 11:47 ` Peter Zijlstra
2022-01-21 15:18 ` Peter Zijlstra
2022-01-24 14:29 ` Peter Zijlstra
2022-01-24 16:44 ` Peter Zijlstra
2022-01-24 17:06 ` Peter Oskolkov
2022-01-25 14:59 ` Peter Zijlstra
2022-01-24 13:59 ` Peter Zijlstra
2022-01-21 12:26 ` Peter Zijlstra
2022-01-21 16:57 ` Mark Rutland
2022-01-24 9:48 ` Peter Zijlstra
2022-01-24 10:03 ` Peter Zijlstra
2022-01-24 10:07 ` Peter Zijlstra
2022-01-24 10:27 ` Mark Rutland
2022-01-24 14:46 ` Tao Zhou
2022-01-27 12:19 ` Peter Zijlstra
2022-01-27 18:33 ` Tao Zhou
2022-01-27 12:25 ` Peter Zijlstra
2022-01-27 18:47 ` Tao Zhou [this message]
2022-01-27 12:26 ` Peter Zijlstra
2022-01-27 18:31 ` Tao Zhou
2022-01-20 17:28 ` [RFC][PATCH v2 0/5] sched: User Managed Concurrency Groups Peter Oskolkov
2022-01-21 8:01 ` Peter Zijlstra
2022-01-21 18:01 ` Steven Rostedt
2022-01-24 8:20 ` Peter Zijlstra
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