From: Peter Zijlstra <peterz@infradead.org>
To: Boqun Feng <boqun.feng@gmail.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
"Paul E . McKenney" <paulmck@linux.vnet.ibm.com>,
linux-kernel@vger.kernel.org, Andrew Hunter <ahh@google.com>,
Maged Michael <maged.michael@gmail.com>,
gromer@google.com, Avi Kivity <avi@scylladb.com>,
Benjamin Herrenschmidt <benh@kernel.crashing.org>,
Paul Mackerras <paulus@samba.org>,
Michael Ellerman <mpe@ellerman.id.au>,
Dave Watson <davejwatson@fb.com>,
Alan Stern <stern@rowland.harvard.edu>,
Will Deacon <will.deacon@arm.com>,
Andy Lutomirski <luto@kernel.org>,
linux-arch@vger.kernel.org
Subject: Re: [RFC PATCH v3 1/2] membarrier: Provide register expedited private command
Date: Fri, 22 Sep 2017 10:24:41 +0200 [thread overview]
Message-ID: <20170922082441.rxavx645ewoizuu2@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20170922032206.GE10893@tardis>
On Fri, Sep 22, 2017 at 11:22:06AM +0800, Boqun Feng wrote:
> The idea is in membarrier_private_expedited(), we go through all ->curr
> on each CPU and
>
> 1) If it's a userspace task and its ->mm is matched, we send an ipi
>
> 2) If it's a kernel task, we skip
>
> (Because there will be a smp_mb() implied by mmdrop(), when it
> switchs to userspace task).
>
> 3) If it's a userspace task and its ->mm is not matched, we take
> the corresponding rq->lock and check rq->curr again, if its ->mm
> matched, we send an ipi, otherwise we do nothing.
>
> (Because if we observe rq->curr is not matched with rq->lock
> held, when a task having matched ->mm schedules in, the rq->lock
> pairing along with the smp_mb__after_spinlock() will guarantee
> it observes all memory ops before sys_membarrir()).
3) is an insta DoS.
next prev parent reply other threads:[~2017-09-22 8:25 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-09-19 22:13 [RFC PATCH v3 1/2] membarrier: Provide register expedited private command Mathieu Desnoyers
2017-09-19 22:13 ` [RFC PATCH 2/2] membarrier: selftest: Test private expedited cmd Mathieu Desnoyers
2017-09-22 3:22 ` [RFC PATCH v3 1/2] membarrier: Provide register expedited private command Boqun Feng
2017-09-22 3:30 ` Boqun Feng
2017-09-22 5:22 ` Mathieu Desnoyers
2017-09-22 8:24 ` Peter Zijlstra [this message]
2017-09-22 8:56 ` Boqun Feng
2017-09-22 8:59 ` Boqun Feng
2017-09-22 15:10 ` Mathieu Desnoyers
2017-09-24 13:30 ` Boqun Feng
2017-09-24 14:23 ` Mathieu Desnoyers
2017-09-25 12:10 ` Boqun Feng
2017-09-25 12:25 ` Peter Zijlstra
2017-09-25 12:42 ` Mathieu Desnoyers
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