[v6,6/7] eal: add failure handle mechanism for hotplug

  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@intel.com>
Acked-by: Shaopeng He <shaopeng.he@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(-)
  

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@intel.com>
> Acked-by: Shaopeng He <shaopeng.he@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;
>   }