[dpdk-dev] [PATCH v6 6/7] eal: add failure handle mechanism for hotplug

[Andrew Rybchenko]

CC Shreyansh

On 09.07.2018 09:01, Jeff Guo wrote:
> This patch introduces a failure handle mechanism to handle device
> hotplug removal event.
>
> First it can register sigbus handler when enable device event monitor. Once
> sigbus error be captured, it will check the failure address and accordingly
> remap the invalid memory for the corresponding device. Besed on this
> mechanism, it could guaranty the application not crash when the device be
> hotplug out.
>
> Signed-off-by: Jeff Guo <jia.guo at intel.com>
> Acked-by: Shaopeng He <shaopeng.he at intel.com>
> ---
> v6->v5:
> refine some doc and coding style
> ---
>   lib/librte_eal/linuxapp/eal/eal_dev.c | 114 +++++++++++++++++++++++++++++++++-
>   1 file changed, 113 insertions(+), 1 deletion(-)
>
> diff --git a/lib/librte_eal/linuxapp/eal/eal_dev.c b/lib/librte_eal/linuxapp/eal/eal_dev.c
> index 1cf6aeb..cb30729 100644
> --- a/lib/librte_eal/linuxapp/eal/eal_dev.c
> +++ b/lib/librte_eal/linuxapp/eal/eal_dev.c
> @@ -4,6 +4,8 @@
>   
>   #include <string.h>
>   #include <unistd.h>
> +#include <fcntl.h>
> +#include <signal.h>
>   #include <sys/socket.h>
>   #include <linux/netlink.h>
>   
> @@ -14,15 +16,31 @@
>   #include <rte_malloc.h>
>   #include <rte_interrupts.h>
>   #include <rte_alarm.h>
> +#include <rte_bus.h>
> +#include <rte_eal.h>
> +#include <rte_spinlock.h>
> +#include <rte_errno.h>
>   
>   #include "eal_private.h"
>   
>   static struct rte_intr_handle intr_handle = {.fd = -1 };
>   static bool monitor_started;
>   
> +extern struct rte_bus_list rte_bus_list;
> +

Shreyansh, shouldn't it be done in rte_bus.h?

>   #define EAL_UEV_MSG_LEN 4096
>   #define EAL_UEV_MSG_ELEM_LEN 128
>   
> +/*
> + * spinlock for device failure process, protect the bus and the device
> + * to avoid race condition.
> + */
> +static rte_spinlock_t dev_failure_lock = RTE_SPINLOCK_INITIALIZER;

Unfortunately it is still not very helpful. I don't understand circumstance
when the race condition could happen.

> +
> +static struct sigaction sigbus_action_old;
> +
> +static int sigbus_need_recover;
> +
>   static void dev_uev_handler(__rte_unused void *param);
>   
>   /* identify the system layer which reports this event. */
> @@ -33,6 +51,49 @@ enum eal_dev_event_subsystem {
>   	EAL_DEV_EVENT_SUBSYSTEM_MAX
>   };
>   
> +static void
> +sigbus_action_recover(void)
> +{
> +	if (sigbus_need_recover) {
> +		sigaction(SIGBUS, &sigbus_action_old, NULL);
> +		sigbus_need_recover = 0;
> +	}
> +}
> +
> +static void sigbus_handler(int signum, siginfo_t *info,
> +				void *ctx __rte_unused)
> +{
> +	int ret;
> +
> +	RTE_LOG(INFO, EAL, "Thread[%d] catch SIGBUS, fault address:%p\n",
> +		(int)pthread_self(), info->si_addr);
> +
> +	rte_spinlock_lock(&dev_failure_lock);
> +	ret = rte_bus_sigbus_handler(info->si_addr);
> +	rte_spinlock_unlock(&dev_failure_lock);
> +	if (ret == -1) {
> +		rte_exit(EXIT_FAILURE,
> +			 "Failed to handle SIGBUS for hotplug, "
> +			 "(rte_errno: %s)!", strerror(rte_errno));
> +	} else if (ret == 1) {
> +		if (sigbus_action_old.sa_handler)
> +			(*(sigbus_action_old.sa_handler))(signum);
> +		else
> +			rte_exit(EXIT_FAILURE,
> +				 "Failed to handle generic SIGBUS!");
> +	}
> +
> +	RTE_LOG(INFO, EAL, "Success to handle SIGBUS for hotplug!\n");
> +}
> +
> +static int cmp_dev_name(const struct rte_device *dev,
> +	const void *_name)
> +{
> +	const char *name = _name;
> +
> +	return strcmp(dev->name, name);
> +}
> +
>   static int
>   dev_uev_socket_fd_create(void)
>   {
> @@ -147,6 +208,9 @@ dev_uev_handler(__rte_unused void *param)
>   	struct rte_dev_event uevent;
>   	int ret;
>   	char buf[EAL_UEV_MSG_LEN];
> +	struct rte_bus *bus;
> +	struct rte_device *dev;
> +	const char *busname = "";
>   
>   	memset(&uevent, 0, sizeof(struct rte_dev_event));
>   	memset(buf, 0, EAL_UEV_MSG_LEN);
> @@ -171,13 +235,50 @@ dev_uev_handler(__rte_unused void *param)
>   	RTE_LOG(DEBUG, EAL, "receive uevent(name:%s, type:%d, subsystem:%d)\n",
>   		uevent.devname, uevent.type, uevent.subsystem);
>   
> -	if (uevent.devname)
> +	switch (uevent.subsystem) {
> +	case EAL_DEV_EVENT_SUBSYSTEM_PCI:
> +	case EAL_DEV_EVENT_SUBSYSTEM_UIO:
> +		busname = "pci";
> +		break;
> +	default:
> +		break;
> +	}
> +
> +	if (uevent.devname) {
> +		if (uevent.type == RTE_DEV_EVENT_REMOVE) {
> +			rte_spinlock_lock(&dev_failure_lock);
> +			bus = rte_bus_find_by_name(busname);

I see no point find bus by empty name. I would suggest to initialize
busname to NULL and simply would not even try to find bus with
such name. Just check above and generate appropriate log.

> +			if (bus == NULL) {
> +				RTE_LOG(ERR, EAL, "Cannot find bus (%s)\n",
> +					busname);
> +				return;
> +			}
> +
> +			dev = bus->find_device(NULL, cmp_dev_name,
> +					       uevent.devname);
> +			if (dev == NULL) {
> +				RTE_LOG(ERR, EAL, "Cannot find device (%s) on "
> +					"bus (%s)\n", uevent.devname, busname);
> +				return;
> +			}
> +
> +			ret = bus->hotplug_failure_handler(dev);
> +			rte_spinlock_unlock(&dev_failure_lock);
> +			if (ret) {
> +				RTE_LOG(ERR, EAL, "Can not handle hotplug for "
> +					"device (%s)\n", dev->name);
> +				return;
> +			}
> +		}
>   		dev_callback_process(uevent.devname, uevent.type);
> +	}
>   }
>   
>   int __rte_experimental
>   rte_dev_event_monitor_start(void)
>   {
> +	sigset_t mask;
> +	struct sigaction action;
>   	int ret;
>   
>   	if (monitor_started)
> @@ -197,6 +298,14 @@ rte_dev_event_monitor_start(void)
>   		return -1;
>   	}
>   
> +	/* register sigbus handler */
> +	sigemptyset(&mask);
> +	sigaddset(&mask, SIGBUS);
> +	action.sa_flags = SA_SIGINFO;
> +	action.sa_mask = mask;
> +	action.sa_sigaction = sigbus_handler;
> +	sigbus_need_recover = !sigaction(SIGBUS, &action, &sigbus_action_old);
> +
>   	monitor_started = true;
>   
>   	return 0;
> @@ -217,8 +326,11 @@ rte_dev_event_monitor_stop(void)
>   		return ret;
>   	}
>   
> +	sigbus_action_recover();
> +
>   	close(intr_handle.fd);
>   	intr_handle.fd = -1;
>   	monitor_started = false;
> +
>   	return 0;
>   }