From: Will Deacon <will@kernel.org>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>,
Juri Lelli <juri.lelli@redhat.com>,
Vincent Guittot <vincent.guittot@linaro.org>,
Dietmar Eggemann <dietmar.eggemann@arm.com>,
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x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>,
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Mike Snitzer <snitzer@redhat.com>,
dm-devel@redhat.com, "David S. Miller" <davem@davemloft.net>,
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Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
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Davidlohr Bueso <dave@stgolabs.net>,
"Paul E. McKenney" <paulmck@kernel.org>,
Josh Triplett <josh@joshtriplett.org>,
Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
Lai Jiangshan <jiangshanlai@gmail.com>,
Joel Fernandes <joel@joelfernandes.org>,
John Stultz <john.stultz@linaro.org>,
Stephen Boyd <sboyd@kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
Paolo Bonzini <pbonzini@redhat.com>,
linux-kernel@vger.kernel.org, linux-block@vger.kernel.org,
netdev@vger.kernel.org, linux-usb@vger.kernel.org,
linux-fsdevel@vger.kernel.org, cgroups@vger.kernel.org,
kgdb-bugreport@lists.sourceforge.net,
linux-perf-users@vger.kernel.org, linux-pm@vger.kernel.org,
rcu@vger.kernel.org, linux-mm@kvack.org, kvm@vger.kernel.org
Subject: Re: [PATCH 1/6] sched: Unbreak wakeups
Date: Wed, 2 Jun 2021 15:47:55 +0100 [thread overview]
Message-ID: <20210602144755.GA31179@willie-the-truck> (raw)
In-Reply-To: <20210602133040.271625424@infradead.org>
On Wed, Jun 02, 2021 at 03:12:26PM +0200, Peter Zijlstra wrote:
> Remove broken task->state references and let wake_up_process() DTRT.
>
> The anti-pattern in these patches breaks the ordering of ->state vs
> COND as described in the comment near set_current_state() and can lead
> to missed wakeups:
>
> (OoO load, observes RUNNING)<-.
> for (;;) { |
> t->state = UNINTERRUPTIBLE; |
> smp_mb(); ,-----> ,' (OoO load, observed !COND)
> | |
> | | COND = 1;
> | `- if (t->state != RUNNING)
> | wake_up_process(t); // not done
> if (COND) ---------'
> break;
> schedule(); // forever waiting
> }
> t->state = TASK_RUNNING;
>
> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
> ---
> drivers/net/ethernet/qualcomm/qca_spi.c | 6 ++----
> drivers/usb/gadget/udc/max3420_udc.c | 15 +++++----------
> drivers/usb/host/max3421-hcd.c | 3 +--
> kernel/softirq.c | 2 +-
> 4 files changed, 9 insertions(+), 17 deletions(-)
Acked-by: Will Deacon <will@kernel.org>
I couldn't spot any others.
Will
next prev parent reply other threads:[~2021-06-02 14:48 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-02 13:12 [PATCH 0/6] sched: Cleanup task_struct::state Peter Zijlstra
2021-06-02 13:12 ` [PATCH 1/6] sched: Unbreak wakeups Peter Zijlstra
2021-06-02 13:58 ` Greg Kroah-Hartman
2021-06-02 14:47 ` Will Deacon [this message]
2021-06-02 19:43 ` Davidlohr Bueso
2021-06-02 13:12 ` [PATCH 2/6] sched: Introduce task_is_running() Peter Zijlstra
2021-06-02 14:59 ` Will Deacon
2021-06-02 16:46 ` Peter Zijlstra
2021-06-02 23:15 ` Davidlohr Bueso
2021-06-02 13:12 ` [PATCH 3/6] sched,perf,kvm: Fix preemption condition Peter Zijlstra
2021-06-02 13:59 ` Mathieu Desnoyers
2021-06-02 14:10 ` Peter Zijlstra
2021-06-02 14:30 ` Mark Rutland
2021-06-02 14:15 ` Mathieu Desnoyers
2021-06-02 14:23 ` Peter Zijlstra
2021-06-02 13:12 ` [PATCH 4/6] sched: Add get_current_state() Peter Zijlstra
2021-06-02 14:01 ` Mathieu Desnoyers
2021-06-02 14:12 ` Peter Zijlstra
2021-06-02 15:02 ` Will Deacon
2021-06-02 13:12 ` [PATCH 5/6] sched,timer: Use __set_current_state() Peter Zijlstra
2021-06-02 15:06 ` Will Deacon
2021-06-02 19:54 ` Davidlohr Bueso
2021-06-03 6:39 ` Peter Zijlstra
2021-06-18 20:42 ` Thomas Gleixner
2021-06-02 13:12 ` [PATCH 6/6] sched: Change task_struct::state Peter Zijlstra
2021-06-02 14:06 ` Mathieu Desnoyers
2021-06-02 14:20 ` Peter Zijlstra
2021-06-02 15:10 ` Will Deacon
2021-06-07 10:45 ` Daniel Thompson
2021-06-07 11:10 ` Peter Zijlstra
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