[PATCH 1/6] sched: Unbreak wakeups
From: Peter Zijlstra <peterz@infradead.org>
Date: 2021-06-02 13:31:17
Also in:
cgroups, dm-devel, kvm, linux-block, linux-fsdevel, linux-mm, linux-perf-users, linux-pm, linux-usb, lkml, rcu
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(-)
--- 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); }