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Message-ID: <20210611082838.160855222@infradead.org>
Date: Fri, 11 Jun 2021 10:28:11 +0200
From: Peter Zijlstra <peterz@...radead.org>
To: Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...hat.com>,
Peter Zijlstra <peterz@...radead.org>,
Juri Lelli <juri.lelli@...hat.com>,
Vincent Guittot <vincent.guittot@...aro.org>,
Dietmar Eggemann <dietmar.eggemann@....com>,
Steven Rostedt <rostedt@...dmis.org>,
Ben Segall <bsegall@...gle.com>, Mel Gorman <mgorman@...e.de>,
Daniel Bristot de Oliveira <bristot@...hat.com>
Cc: Borislav Petkov <bp@...en8.de>, x86@...nel.org,
"H. Peter Anvin" <hpa@...or.com>, Jens Axboe <axboe@...nel.dk>,
Alasdair Kergon <agk@...hat.com>,
Mike Snitzer <snitzer@...hat.com>,
"David S. Miller" <davem@...emloft.net>,
Jakub Kicinski <kuba@...nel.org>,
Felipe Balbi <balbi@...nel.org>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Alexander Viro <viro@...iv.linux.org.uk>,
Tejun Heo <tj@...nel.org>, Zefan Li <lizefan.x@...edance.com>,
Johannes Weiner <hannes@...xchg.org>,
Jason Wessel <jason.wessel@...driver.com>,
Daniel Thompson <daniel.thompson@...aro.org>,
Douglas Anderson <dianders@...omium.org>,
Arnaldo Carvalho de Melo <acme@...nel.org>,
Mark Rutland <mark.rutland@....com>,
Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
Jiri Olsa <jolsa@...hat.com>,
Namhyung Kim <namhyung@...nel.org>,
"Rafael J. Wysocki" <rjw@...ysocki.net>,
Pavel Machek <pavel@....cz>, Will Deacon <will@...nel.org>,
Waiman Long <longman@...hat.com>,
Boqun Feng <boqun.feng@...il.com>,
Oleg Nesterov <oleg@...hat.com>,
Davidlohr Bueso <dave@...olabs.net>,
"Paul E. McKenney" <paulmck@...nel.org>,
Josh Triplett <josh@...htriplett.org>,
Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
Lai Jiangshan <jiangshanlai@...il.com>,
Joel Fernandes <joel@...lfernandes.org>,
John Stultz <john.stultz@...aro.org>,
Stephen Boyd <sboyd@...nel.org>,
Andrew Morton <akpm@...ux-foundation.org>,
Paolo Bonzini <pbonzini@...hat.com>,
Stephen Rothwell <sfr@...b.auug.org.au>,
linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org,
Davidlohr Bueso <dbueso@...e.de>
Subject: [PATCH v2 1/7] sched: Unbreak wakeups
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(); ,-----> | (observes !COND)
| /
if (COND) ---------' | COND = 1;
break; `- if (t->state != RUNNING)
wake_up_process(t); // not done
schedule(); // forever waiting
}
t->state = TASK_RUNNING;
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Reviewed-by: Davidlohr Bueso <dbueso@...e.de>
Acked-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Acked-by: Will Deacon <will@...nel.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(-)
--- a/drivers/net/ethernet/qualcomm/qca_spi.c
+++ b/drivers/net/ethernet/qualcomm/qca_spi.c
@@ -653,8 +653,7 @@ qcaspi_intr_handler(int irq, void *data)
struct qcaspi *qca = data;
qca->intr_req++;
- if (qca->spi_thread &&
- qca->spi_thread->state != TASK_RUNNING)
+ if (qca->spi_thread)
wake_up_process(qca->spi_thread);
return IRQ_HANDLED;
@@ -777,8 +776,7 @@ qcaspi_netdev_xmit(struct sk_buff *skb,
netif_trans_update(dev);
- if (qca->spi_thread &&
- qca->spi_thread->state != TASK_RUNNING)
+ if (qca->spi_thread)
wake_up_process(qca->spi_thread);
return NETDEV_TX_OK;
--- a/drivers/usb/gadget/udc/max3420_udc.c
+++ b/drivers/usb/gadget/udc/max3420_udc.c
@@ -509,8 +509,7 @@ static irqreturn_t max3420_vbus_handler(
? USB_STATE_POWERED : USB_STATE_NOTATTACHED);
spin_unlock_irqrestore(&udc->lock, flags);
- if (udc->thread_task &&
- udc->thread_task->state != TASK_RUNNING)
+ if (udc->thread_task)
wake_up_process(udc->thread_task);
return IRQ_HANDLED;
@@ -529,8 +528,7 @@ static irqreturn_t max3420_irq_handler(i
}
spin_unlock_irqrestore(&udc->lock, flags);
- if (udc->thread_task &&
- udc->thread_task->state != TASK_RUNNING)
+ if (udc->thread_task)
wake_up_process(udc->thread_task);
return IRQ_HANDLED;
@@ -1093,8 +1091,7 @@ static int max3420_wakeup(struct usb_gad
spin_unlock_irqrestore(&udc->lock, flags);
- if (udc->thread_task &&
- udc->thread_task->state != TASK_RUNNING)
+ if (udc->thread_task)
wake_up_process(udc->thread_task);
return ret;
}
@@ -1117,8 +1114,7 @@ static int max3420_udc_start(struct usb_
udc->todo |= UDC_START;
spin_unlock_irqrestore(&udc->lock, flags);
- if (udc->thread_task &&
- udc->thread_task->state != TASK_RUNNING)
+ if (udc->thread_task)
wake_up_process(udc->thread_task);
return 0;
@@ -1137,8 +1133,7 @@ static int max3420_udc_stop(struct usb_g
udc->todo |= UDC_START;
spin_unlock_irqrestore(&udc->lock, flags);
- if (udc->thread_task &&
- udc->thread_task->state != TASK_RUNNING)
+ if (udc->thread_task)
wake_up_process(udc->thread_task);
return 0;
--- a/drivers/usb/host/max3421-hcd.c
+++ b/drivers/usb/host/max3421-hcd.c
@@ -1169,8 +1169,7 @@ max3421_irq_handler(int irq, void *dev_i
struct spi_device *spi = to_spi_device(hcd->self.controller);
struct max3421_hcd *max3421_hcd = hcd_to_max3421(hcd);
- if (max3421_hcd->spi_thread &&
- max3421_hcd->spi_thread->state != TASK_RUNNING)
+ if (max3421_hcd->spi_thread)
wake_up_process(max3421_hcd->spi_thread);
if (!test_and_set_bit(ENABLE_IRQ, &max3421_hcd->todo))
disable_irq_nosync(spi->irq);
--- a/kernel/softirq.c
+++ b/kernel/softirq.c
@@ -76,7 +76,7 @@ static void wakeup_softirqd(void)
/* Interrupts are disabled: no need to stop preemption */
struct task_struct *tsk = __this_cpu_read(ksoftirqd);
- if (tsk && tsk->state != TASK_RUNNING)
+ if (tsk)
wake_up_process(tsk);
}
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