diff mbox

PCI: Mediatek: clear irq status after irq dispathed to avoid reentry

Message ID 1513738334-26213-1-git-send-email-honghui.zhang@mediatek.com (mailing list archive)
State New, archived
Delegated to: Bjorn Helgaas
Headers show

Commit Message

Honghui Zhang Dec. 20, 2017, 2:52 a.m. UTC 
From: Honghui Zhang <honghui.zhang@mediatek.com>

There maybe a same irq reentry scenario after irq received in current
irq handle flow:
	EP device		PCIe host driver	EP driver
1. issue an irq
			2. received irq
			3. clear irq status
			4. dispatch irq
						5. clear irq source
The irq status was not successfully cleared at step 2 since the irq
source was not cleared yet. So the PCIe host driver may receive the
same irq after step 5. Then there's an irq reentry occurred.
Even worse, if the reentry irq was not an irq that EP driver expected,
it may not handle the irq. Then we may run into the dead loop from
step 2 to step 4.
Clear the irq status after irq have been dispatched to avoid the irq
reentry.

Signed-off-by: Honghui Zhang <honghui.zhang@mediatek.com>
---
 drivers/pci/host/pcie-mediatek.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

Comments

Ryder Lee Dec. 20, 2017, 3:08 a.m. UTC | #1 
On Wed, 2017-12-20 at 10:52 +0800, honghui.zhang@mediatek.com wrote:
> From: Honghui Zhang <honghui.zhang@mediatek.com>
> 
> There maybe a same irq reentry scenario after irq received in current
> irq handle flow:
> 	EP device		PCIe host driver	EP driver
> 1. issue an irq
> 			2. received irq
> 			3. clear irq status
> 			4. dispatch irq
> 						5. clear irq source
> The irq status was not successfully cleared at step 2 since the irq
> source was not cleared yet. So the PCIe host driver may receive the
> same irq after step 5. Then there's an irq reentry occurred.
> Even worse, if the reentry irq was not an irq that EP driver expected,
> it may not handle the irq. Then we may run into the dead loop from
> step 2 to step 4.
> Clear the irq status after irq have been dispatched to avoid the irq
> reentry.
> 
> Signed-off-by: Honghui Zhang <honghui.zhang@mediatek.com>
> ---
>  drivers/pci/host/pcie-mediatek.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/pci/host/pcie-mediatek.c b/drivers/pci/host/pcie-mediatek.c
> index db93efd..3248771 100644
> --- a/drivers/pci/host/pcie-mediatek.c
> +++ b/drivers/pci/host/pcie-mediatek.c
> @@ -605,11 +605,11 @@ static irqreturn_t mtk_pcie_intr_handler(int irq, void *data)
>  
>  	while ((status = readl(port->base + PCIE_INT_STATUS)) & INTX_MASK) {
>  		for_each_set_bit_from(bit, &status, PCI_NUM_INTX + INTX_SHIFT) {
> -			/* Clear the INTx */
> -			writel(1 << bit, port->base + PCIE_INT_STATUS);
>  			virq = irq_find_mapping(port->irq_domain,
>  						bit - INTX_SHIFT);
>  			generic_handle_irq(virq);
> +			/* Clear the INTx */
> +			writel(1 << bit, port->base + PCIE_INT_STATUS);
>  		}
>  	}
>  
> @@ -619,10 +619,10 @@ static irqreturn_t mtk_pcie_intr_handler(int irq, void *data)
>  
>  			while ((imsi_status = readl(port->base + PCIE_IMSI_STATUS))) {
>  				for_each_set_bit(bit, &imsi_status, MTK_MSI_IRQS_NUM) {
> -					/* Clear the MSI */
> -					writel(1 << bit, port->base + PCIE_IMSI_STATUS);
>  					virq = irq_find_mapping(port->msi_domain, bit);
>  					generic_handle_irq(virq);
> +					/* Clear the MSI */
> +					writel(1 << bit, port->base + PCIE_IMSI_STATUS);
>  				}
>  			}
>  			/* Clear MSI interrupt status */

Acked-by: Ryder Lee <ryder.lee@mediatek.com>

Thanks.
Bjorn Helgaas Dec. 21, 2017, 12:52 a.m. UTC | #2 
[+cc Lorenzo, please cc him on all drivers/{host,dwc,endpoint} material]

Please run "git log --oneline drivers/pci/host/pcie-mediatek.c" and
make yours match.  Same capitalization, same sentence structure, etc.,
e.g.,

  PCI: mediatek: Clear IRQ status ...

s/dispathed/dispatched/

s/irq/IRQ/ in the summary and all the English text below.

On Wed, Dec 20, 2017 at 10:52:14AM +0800, honghui.zhang@mediatek.com wrote:
> From: Honghui Zhang <honghui.zhang@mediatek.com>
> 
> There maybe a same irq reentry scenario after irq received in current
> irq handle flow:
> 	EP device		PCIe host driver	EP driver
> 1. issue an irq
> 			2. received irq
> 			3. clear irq status
> 			4. dispatch irq
> 						5. clear irq source
> The irq status was not successfully cleared at step 2 since the irq
> source was not cleared yet. So the PCIe host driver may receive the
> same irq after step 5. Then there's an irq reentry occurred.
> Even worse, if the reentry irq was not an irq that EP driver expected,
> it may not handle the irq. Then we may run into the dead loop from

By "dead loop" I assume you mean "infinite loop"?  I don't think it's
a deadlock since nothing is waiting.

> step 2 to step 4.
> Clear the irq status after irq have been dispatched to avoid the irq
> reentry.
> 
> Signed-off-by: Honghui Zhang <honghui.zhang@mediatek.com>
> ---
>  drivers/pci/host/pcie-mediatek.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/pci/host/pcie-mediatek.c b/drivers/pci/host/pcie-mediatek.c
> index db93efd..3248771 100644
> --- a/drivers/pci/host/pcie-mediatek.c
> +++ b/drivers/pci/host/pcie-mediatek.c
> @@ -605,11 +605,11 @@ static irqreturn_t mtk_pcie_intr_handler(int irq, void *data)
>  
>  	while ((status = readl(port->base + PCIE_INT_STATUS)) & INTX_MASK) {
>  		for_each_set_bit_from(bit, &status, PCI_NUM_INTX + INTX_SHIFT) {
> -			/* Clear the INTx */
> -			writel(1 << bit, port->base + PCIE_INT_STATUS);
>  			virq = irq_find_mapping(port->irq_domain,
>  						bit - INTX_SHIFT);
>  			generic_handle_irq(virq);
> +			/* Clear the INTx */
> +			writel(1 << bit, port->base + PCIE_INT_STATUS);
>  		}
>  	}
>  
> @@ -619,10 +619,10 @@ static irqreturn_t mtk_pcie_intr_handler(int irq, void *data)
>  
>  			while ((imsi_status = readl(port->base + PCIE_IMSI_STATUS))) {
>  				for_each_set_bit(bit, &imsi_status, MTK_MSI_IRQS_NUM) {
> -					/* Clear the MSI */
> -					writel(1 << bit, port->base + PCIE_IMSI_STATUS);
>  					virq = irq_find_mapping(port->msi_domain, bit);
>  					generic_handle_irq(virq);
> +					/* Clear the MSI */
> +					writel(1 << bit, port->base + PCIE_IMSI_STATUS);
>  				}
>  			}
>  			/* Clear MSI interrupt status */
> -- 
> 2.6.4
> 
> 
> _______________________________________________
> linux-arm-kernel mailing list
> linux-arm-kernel@lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
Honghui Zhang Dec. 21, 2017, 1:37 a.m. UTC | #3 
On Wed, 2017-12-20 at 18:52 -0600, Bjorn Helgaas wrote:
> [+cc Lorenzo, please cc him on all drivers/{host,dwc,endpoint} material]
> 
> Please run "git log --oneline drivers/pci/host/pcie-mediatek.c" and
> make yours match.  Same capitalization, same sentence structure, etc.,
> e.g.,
> 
>   PCI: mediatek: Clear IRQ status ...
> 
> s/dispathed/dispatched/
> 
> s/irq/IRQ/ in the summary and all the English text below.

Thanks for your review and sorry for the mismatch, I will fix that in
next version.

> 
> On Wed, Dec 20, 2017 at 10:52:14AM +0800, honghui.zhang@mediatek.com wrote:
> > From: Honghui Zhang <honghui.zhang@mediatek.com>
> > 
> > There maybe a same irq reentry scenario after irq received in current
> > irq handle flow:
> > 	EP device		PCIe host driver	EP driver
> > 1. issue an irq
> > 			2. received irq
> > 			3. clear irq status
> > 			4. dispatch irq
> > 						5. clear irq source
> > The irq status was not successfully cleared at step 2 since the irq
> > source was not cleared yet. So the PCIe host driver may receive the
> > same irq after step 5. Then there's an irq reentry occurred.
> > Even worse, if the reentry irq was not an irq that EP driver expected,
> > it may not handle the irq. Then we may run into the dead loop from
> 
> By "dead loop" I assume you mean "infinite loop"?  I don't think it's
> a deadlock since nothing is waiting.
> 
Yes, it should be "infinite loop", I will update the commit message in
next version.

thanks.
> > step 2 to step 4.
> > Clear the irq status after irq have been dispatched to avoid the irq
> > reentry.
> > 
> > Signed-off-by: Honghui Zhang <honghui.zhang@mediatek.com>
> > ---
> >  drivers/pci/host/pcie-mediatek.c | 8 ++++----
> >  1 file changed, 4 insertions(+), 4 deletions(-)
> > 
> > diff --git a/drivers/pci/host/pcie-mediatek.c b/drivers/pci/host/pcie-mediatek.c
> > index db93efd..3248771 100644
> > --- a/drivers/pci/host/pcie-mediatek.c
> > +++ b/drivers/pci/host/pcie-mediatek.c
> > @@ -605,11 +605,11 @@ static irqreturn_t mtk_pcie_intr_handler(int irq, void *data)
> >  
> >  	while ((status = readl(port->base + PCIE_INT_STATUS)) & INTX_MASK) {
> >  		for_each_set_bit_from(bit, &status, PCI_NUM_INTX + INTX_SHIFT) {
> > -			/* Clear the INTx */
> > -			writel(1 << bit, port->base + PCIE_INT_STATUS);
> >  			virq = irq_find_mapping(port->irq_domain,
> >  						bit - INTX_SHIFT);
> >  			generic_handle_irq(virq);
> > +			/* Clear the INTx */
> > +			writel(1 << bit, port->base + PCIE_INT_STATUS);
> >  		}
> >  	}
> >  
> > @@ -619,10 +619,10 @@ static irqreturn_t mtk_pcie_intr_handler(int irq, void *data)
> >  
> >  			while ((imsi_status = readl(port->base + PCIE_IMSI_STATUS))) {
> >  				for_each_set_bit(bit, &imsi_status, MTK_MSI_IRQS_NUM) {
> > -					/* Clear the MSI */
> > -					writel(1 << bit, port->base + PCIE_IMSI_STATUS);
> >  					virq = irq_find_mapping(port->msi_domain, bit);
> >  					generic_handle_irq(virq);
> > +					/* Clear the MSI */
> > +					writel(1 << bit, port->base + PCIE_IMSI_STATUS);
> >  				}
> >  			}
> >  			/* Clear MSI interrupt status */
> > -- 
> > 2.6.4
> > 
> > 
> > _______________________________________________
> > linux-arm-kernel mailing list
> > linux-arm-kernel@lists.infradead.org
> > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
diff mbox

Patch

diff --git a/drivers/pci/host/pcie-mediatek.c b/drivers/pci/host/pcie-mediatek.c
index db93efd..3248771 100644
--- a/drivers/pci/host/pcie-mediatek.c
+++ b/drivers/pci/host/pcie-mediatek.c
@@ -605,11 +605,11 @@  static irqreturn_t mtk_pcie_intr_handler(int irq, void *data)
 
 	while ((status = readl(port->base + PCIE_INT_STATUS)) & INTX_MASK) {
 		for_each_set_bit_from(bit, &status, PCI_NUM_INTX + INTX_SHIFT) {
-			/* Clear the INTx */
-			writel(1 << bit, port->base + PCIE_INT_STATUS);
 			virq = irq_find_mapping(port->irq_domain,
 						bit - INTX_SHIFT);
 			generic_handle_irq(virq);
+			/* Clear the INTx */
+			writel(1 << bit, port->base + PCIE_INT_STATUS);
 		}
 	}
 
@@ -619,10 +619,10 @@  static irqreturn_t mtk_pcie_intr_handler(int irq, void *data)
 
 			while ((imsi_status = readl(port->base + PCIE_IMSI_STATUS))) {
 				for_each_set_bit(bit, &imsi_status, MTK_MSI_IRQS_NUM) {
-					/* Clear the MSI */
-					writel(1 << bit, port->base + PCIE_IMSI_STATUS);
 					virq = irq_find_mapping(port->msi_domain, bit);
 					generic_handle_irq(virq);
+					/* Clear the MSI */
+					writel(1 << bit, port->base + PCIE_IMSI_STATUS);
 				}
 			}
 			/* Clear MSI interrupt status */