Re: [dpdk-dev] [PATCH 2/3] vfio: fix to add handler lock for hot-unplug

[Matan Azrad <matan@mellanox.com>]

Hi Jeff

Can you detail more in the commit log that we can understand the synchronization problematic scenario. And how does this commit fix it? 


> -----Original Message-----
> From: Jeff Guo <jia.guo@intel.com>
> Sent: Tuesday, November 6, 2018 8:07 AM
> To: konstantin.ananyev@intel.com; anatoly.burakov@intel.com; Thomas
> Monjalon <thomas@monjalon.net>; bernard.iremonger@intel.com;
> jingjing.wu@intel.com; wenzhuo.lu@intel.com
> Cc: ferruh.yigit@intel.com; dev@dpdk.org; jia.guo@intel.com;
> helin.zhang@intel.com; Matan Azrad <matan@mellanox.com>;
> shaopeng.he@intel.com
> Subject: [PATCH 2/3] vfio: fix to add handler lock for hot-unplug
> 
> This patch add hot-unplug handler lock and unlock in device request handler
> when process bus and device resource, in order to avoid the synchronization
> issue when device be hot-unplugged.
> 
> Fixes: c115fd000c32 ("vfio: handle hotplug request notifier")
> Signed-off-by: Jeff Guo <jia.guo@intel.com>
> ---
>  drivers/bus/pci/linux/pci_vfio.c | 14 +++++++++++++-
>  1 file changed, 13 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/bus/pci/linux/pci_vfio.c b/drivers/bus/pci/linux/pci_vfio.c
> index 305cc06..d2c8410 100644
> --- a/drivers/bus/pci/linux/pci_vfio.c
> +++ b/drivers/bus/pci/linux/pci_vfio.c
> @@ -19,6 +19,7 @@
>  #include <rte_vfio.h>
>  #include <rte_eal.h>
>  #include <rte_bus.h>
> +#include <rte_spinlock.h>
> 
>  #include "eal_filesystem.h"
> 
> @@ -35,6 +36,14 @@
>   * This file is only compiled if CONFIG_RTE_EAL_VFIO is set to "y".
>   */
> 
> +/*
> + * spinlock for device hot-unplug failure handling. If it try to access
> +bus or
> + * device, such as handle sigbus on bus or handle memory failure for
> +device
> + * just need to use this lock. It could protect the bus and the device
> +to avoid
> + * race condition.
> + */
> +static rte_spinlock_t failure_handle_lock = RTE_SPINLOCK_INITIALIZER;
> +
>  #ifdef VFIO_PRESENT
> 
>  #ifndef PAGE_SIZE
> @@ -289,11 +298,12 @@ pci_vfio_req_handler(void *param)
>  	int ret;
>  	struct rte_device *device = (struct rte_device *)param;
> 
> +	rte_spinlock_lock(&failure_handle_lock);
>  	bus = rte_bus_find_by_device(device);
>  	if (bus == NULL) {
>  		RTE_LOG(ERR, EAL, "Cannot find bus for device (%s)\n",
>  			device->name);
> -		return;
> +		goto handle_end;
>  	}
> 
>  	/*
> @@ -306,6 +316,8 @@ pci_vfio_req_handler(void *param)
>  		RTE_LOG(ERR, EAL,
>  			"Can not handle hot-unplug for device (%s)\n",
>  			device->name);
> +handle_end:
> +	rte_spinlock_unlock(&failure_handle_lock);
>  }
> 
>  /* enable notifier (only enable req now) */
> --
> 2.7.4