Re: [PATCH v11 6/7] eal: add failure handle mechanism for hot-unplug

["Ananyev, Konstantin" <konstantin.ananyev@intel.com>]

Hi Jeff,

> 
> The mechanism can initially register the sigbus handler after the device
> event monitor is enabled. When a sigbus event is captured, it will check
> the failure address and accordingly handle the memory failure of the
> corresponding device by invoke the hot-unplug handler. It could prevent
> the application from crashing when a device is hot-unplugged.
> 
> By this patch, users could call below new added APIs to enable/disable
> the device hotplug handle mechanism. Note that it just implement the
> hot-unplug handler in these functions, the other handler of hotplug, such
> as handler for hotplug binding, could be add in the future if need:
>   - rte_dev_hotplug_handle_enable
>   - rte_dev_hotplug_handle_disable
> 
> Signed-off-by: Jeff Guo <jia.guo@intel.com>
> Acked-by: Shaopeng He <shaopeng.he@intel.com>
> ---
> v11->v10:
> change some words and change the invoked func name.
> add experimental tag
> ---
>  doc/guides/rel_notes/release_18_08.rst  |   5 +
>  lib/librte_eal/bsdapp/eal/eal_dev.c     |  14 +++
>  lib/librte_eal/common/eal_private.h     |  26 +++++
>  lib/librte_eal/common/include/rte_dev.h |  26 +++++
>  lib/librte_eal/linuxapp/eal/eal_dev.c   | 162 +++++++++++++++++++++++++++++++-
>  lib/librte_eal/rte_eal_version.map      |   2 +
>  6 files changed, 234 insertions(+), 1 deletion(-)
> 
> diff --git a/doc/guides/rel_notes/release_18_08.rst b/doc/guides/rel_notes/release_18_08.rst
> index 321fa84..fe0e60f 100644
> --- a/doc/guides/rel_notes/release_18_08.rst
> +++ b/doc/guides/rel_notes/release_18_08.rst
> @@ -117,6 +117,11 @@ New Features
> 
>    Added support for chained mbufs (input and output).
> 
> +* **Added hot-unplug handle mechanism.**
> +
> +  ``rte_dev_hotplug_handle_enable`` and ``rte_dev_hotplug_handle_disable`` are
> +  for enabling or disabling hotplug handle mechanism.
> +
> 
>  API Changes
>  -----------
> diff --git a/lib/librte_eal/bsdapp/eal/eal_dev.c b/lib/librte_eal/bsdapp/eal/eal_dev.c
> index 1c6c51b..255d611 100644
> --- a/lib/librte_eal/bsdapp/eal/eal_dev.c
> +++ b/lib/librte_eal/bsdapp/eal/eal_dev.c
> @@ -19,3 +19,17 @@ rte_dev_event_monitor_stop(void)
>  	RTE_LOG(ERR, EAL, "Device event is not supported for FreeBSD\n");
>  	return -1;
>  }
> +
> +int __rte_experimental
> +rte_dev_hotplug_handle_enable(void)
> +{
> +	RTE_LOG(ERR, EAL, "Device event is not supported for FreeBSD\n");
> +	return -1;
> +}
> +
> +int __rte_experimental
> +rte_dev_hotplug_handle_disable(void)
> +{
> +	RTE_LOG(ERR, EAL, "Device event is not supported for FreeBSD\n");
> +	return -1;
> +}
> diff --git a/lib/librte_eal/common/eal_private.h b/lib/librte_eal/common/eal_private.h
> index a2d1528..637f20d 100644
> --- a/lib/librte_eal/common/eal_private.h
> +++ b/lib/librte_eal/common/eal_private.h
> @@ -317,4 +317,30 @@ rte_devargs_layers_parse(struct rte_devargs *devargs,
>   */
>  int rte_bus_sigbus_handler(const void *failure_addr);
> 
> +/**
> + * @warning
> + * @b EXPERIMENTAL: this API may change without prior notice
> + *
> + * Register the sigbus handler.
> + *
> + * @return
> + *   - On success, zero.
> + *   - On failure, a negative value.
> + */
> +int
> +rte_dev_sigbus_handler_register(void);
> +
> +/**
> + * @warning
> + * @b EXPERIMENTAL: this API may change without prior notice
> + *
> + * Unregister the sigbus handler.
> + *
> + * @return
> + *   - On success, zero.
> + *   - On failure, a negative value.
> + */
> +int
> +rte_dev_sigbus_handler_unregister(void);
> +
>  #endif /* _EAL_PRIVATE_H_ */
> diff --git a/lib/librte_eal/common/include/rte_dev.h b/lib/librte_eal/common/include/rte_dev.h
> index b80a805..ff580a0 100644
> --- a/lib/librte_eal/common/include/rte_dev.h
> +++ b/lib/librte_eal/common/include/rte_dev.h
> @@ -460,4 +460,30 @@ rte_dev_event_monitor_start(void);
>  int __rte_experimental
>  rte_dev_event_monitor_stop(void);
> 
> +/**
> + * @warning
> + * @b EXPERIMENTAL: this API may change without prior notice
> + *
> + * Enable hotplug handling for devices.
> + *
> + * @return
> + *   - On success, zero.
> + *   - On failure, a negative value.
> + */
> +int __rte_experimental
> +rte_dev_hotplug_handle_enable(void);
> +
> +/**
> + * @warning
> + * @b EXPERIMENTAL: this API may change without prior notice
> + *
> + * Disable hotplug handling for devices.
> + *
> + * @return
> + *   - On success, zero.
> + *   - On failure, a negative value.
> + */
> +int __rte_experimental
> +rte_dev_hotplug_handle_disable(void);
> +
>  #endif /* _RTE_DEV_H_ */
> diff --git a/lib/librte_eal/linuxapp/eal/eal_dev.c b/lib/librte_eal/linuxapp/eal/eal_dev.c
> index 1cf6aeb..14b18d8 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 +16,32 @@
>  #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;
> +static bool hotplug_handle;
> 
>  #define EAL_UEV_MSG_LEN 4096
>  #define EAL_UEV_MSG_ELEM_LEN 128
> 
> +/*
> + * 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;
> +
> +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 +52,49 @@ 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(&failure_handle_lock);
> +	ret = rte_bus_sigbus_handler(info->si_addr);
> +	rte_spinlock_unlock(&failure_handle_lock);
> +	if (ret == -1) {
> +		rte_exit(EXIT_FAILURE,
> +			 "Failed to handle SIGBUS for hot-unplug, "
> +			 "(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 hot-unplug!\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 +209,9 @@ 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);
> @@ -171,8 +236,43 @@ 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 && hotplug_handle) {
> +			rte_spinlock_lock(&failure_handle_lock);
> +			bus = rte_bus_find_by_name(busname);
> +			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->hot_unplug_handler(dev);
> +			rte_spinlock_unlock(&failure_handle_lock);
> +			if (ret) {
> +				RTE_LOG(ERR, EAL, "Can not handle hot-unplug "
> +					"for device (%s)\n", dev->name);
> +				return;
> +			}
> +		}
>  		dev_callback_process(uevent.devname, uevent.type);
> +	}
>  }
> 
>  int __rte_experimental
> @@ -220,5 +320,65 @@ rte_dev_event_monitor_stop(void)
>  	close(intr_handle.fd);
>  	intr_handle.fd = -1;
>  	monitor_started = false;
> +
>  	return 0;
>  }
> +
> +int __rte_experimental
> +rte_dev_sigbus_handler_register(void)
> +{
> +	sigset_t mask;
> +	struct sigaction action;
> +
> +	rte_errno = 0;
> +

Shouldn't you call sigaction only if sigbus_need_recover == 0?

> +	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);
> +
> +	return rte_errno;
> +}
> +
> +int __rte_experimental
> +rte_dev_sigbus_handler_unregister(void)
> +{
> +	rte_errno = 0;
> +	sigbus_need_recover = 1;

Hmm, why to set sugbus_need_recover to 1 here?
If user called rte_dev_sigbus_handler_register() before, and it was successful, it already would be 1.
In other cases, you probably don't have to do anything.
Konstantin

> +
> +	sigbus_action_recover();
> +
> +	return rte_errno;
> +}
> +
> +int __rte_experimental
> +rte_dev_hotplug_handle_enable(void)
> +{
> +	int ret = 0;
> +
> +	ret = rte_dev_sigbus_handler_register();
> +	if (ret < 0)
> +		RTE_LOG(ERR, EAL, "fail to register sigbus handler for "
> +			"devices.\n");
> +
> +	hotplug_handle = true;
> +
> +	return ret;
> +}
> +
> +int __rte_experimental
> +rte_dev_hotplug_handle_disable(void)
> +{
> +	int ret = 0;
> +
> +	ret = rte_dev_sigbus_handler_unregister();
> +	if (ret < 0)
> +		RTE_LOG(ERR, EAL, "fail to unregister sigbus handler for "
> +			"devices.\n");
> +
> +	hotplug_handle = false;
> +
> +	return ret;
> +}
> diff --git a/lib/librte_eal/rte_eal_version.map b/lib/librte_eal/rte_eal_version.map
> index 73282bb..a3255aa 100644
> --- a/lib/librte_eal/rte_eal_version.map
> +++ b/lib/librte_eal/rte_eal_version.map
> @@ -281,6 +281,8 @@ EXPERIMENTAL {
>  	rte_dev_event_callback_unregister;
>  	rte_dev_event_monitor_start;
>  	rte_dev_event_monitor_stop;
> +	rte_dev_hotplug_handle_enable;
> +	rte_dev_hotplug_handle_disable;
>  	rte_dev_iterator_init;
>  	rte_dev_iterator_next;
>  	rte_devargs_add;
> --
> 2.7.4