Re: [PATCH] pci-hyperv: do not sleep in compose_msi_msg

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On Mon, Jul 31, 2017 at 04:48:29PM -0700, Stephen Hemminger wrote:
> The setup of MSI with Hyper-V host was sleeping with locks held.
> This error is reported when doing SR-IOV hotplug with kernel built with lockdep.
> 
>     BUG: sleeping function called from invalid context at kernel/sched/completion.c:93
>     in_atomic(): 1, irqs_disabled(): 1, pid: 1405, name: ip
>     3 locks held by ip/1405:
>    #0:  (rtnl_mutex){+.+.+.}, at: [<ffffffff976b10bb>] rtnetlink_rcv+0x1b/0x40
>    #1:  (&desc->request_mutex){+.+...}, at: [<ffffffff970ddd33>] __setup_irq+0xb3/0x720
>    #2:  (&irq_desc_lock_class){-.-...}, at: [<ffffffff970ddd65>] __setup_irq+0xe5/0x720
>    irq event stamp: 3476
>    hardirqs last  enabled at (3475): [<ffffffff971b3005>] get_page_from_freelist+0x225/0xc90
>    hardirqs last disabled at (3476): [<ffffffff978024e7>] _raw_spin_lock_irqsave+0x27/0x90
>    softirqs last  enabled at (2446): [<ffffffffc05ef0b0>] ixgbevf_configure+0x380/0x7c0 [ixgbevf]
>    softirqs last disabled at (2444): [<ffffffffc05ef08d>] ixgbevf_configure+0x35d/0x7c0 [ixgbevf]
> 
> The workaround is to poll for host response instead of blocking on
> completion.
> 
> Signed-off-by: Stephen Hemminger <sthemmin@xxxxxxxxxxxxx>

Applied to pci/host-hv for v4.14, thanks!

> ---
>  drivers/pci/host/pci-hyperv.c | 8 +++++++-
>  1 file changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/pci/host/pci-hyperv.c b/drivers/pci/host/pci-hyperv.c
> index 415dcc69a502..334c9a7b8991 100644
> --- a/drivers/pci/host/pci-hyperv.c
> +++ b/drivers/pci/host/pci-hyperv.c
> @@ -50,6 +50,7 @@
>  #include <linux/kernel.h>
>  #include <linux/module.h>
>  #include <linux/pci.h>
> +#include <linux/delay.h>
>  #include <linux/semaphore.h>
>  #include <linux/irqdomain.h>
>  #include <asm/irqdomain.h>
> @@ -1159,7 +1160,12 @@ static void hv_compose_msi_msg(struct irq_data *data, struct msi_msg *msg)
>  		goto free_int_desc;
>  	}
>  
> -	wait_for_completion(&comp.comp_pkt.host_event);
> +	/*
> +	 * Since this function is called with IRQ locks held, can't
> +	 * do normal wait for completion; instead poll.
> +	 */
> +	while (!try_wait_for_completion(&comp.comp_pkt.host_event))
> +		udelay(100);
>  
>  	if (comp.comp_pkt.completion_status < 0) {
>  		dev_err(&hbus->hdev->device,
> -- 
> 2.11.0
> 



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