Re: [dpdk-dev] [PATCH V19 2/4] eal: add failure handler mechanism for hot plug

["Zhang, Qi Z" <qi.z.zhang@intel.com>]

Hi Jeff:

> -----Original Message-----
> From: dev [mailto:dev-bounces@dpdk.org] On Behalf Of Jeff Guo
> Sent: Friday, April 6, 2018 6:57 PM
> To: stephen@networkplumber.org; Richardson, Bruce
> <bruce.richardson@intel.com>; Yigit, Ferruh <ferruh.yigit@intel.com>;
> Ananyev, Konstantin <konstantin.ananyev@intel.com>;
> gaetan.rivet@6wind.com; Wu, Jingjing <jingjing.wu@intel.com>;
> thomas@monjalon.net; motih@mellanox.com; Van Haaren, Harry
> <harry.van.haaren@intel.com>; Tan, Jianfeng <jianfeng.tan@intel.com>
> Cc: jblunck@infradead.org; shreyansh.jain@nxp.com; dev@dpdk.org; Guo, Jia
> <jia.guo@intel.com>; Zhang, Helin <helin.zhang@intel.com>
> Subject: [dpdk-dev] [PATCH V19 2/4] eal: add failure handler mechanism for
> hot plug
> 
> This patch introduces an API (rte_dev_handle_hot_unplug) to handle device
> hot unplug event. When device be hot plug out, the device resource become
> invalid, if this resource is still be unexpected read/write, system will crash. The
> api let user register the hot unplug handler, when hot plug failure occur, the
> working thread will be block until the uevent mechanism successful recovery
> the memory and guaranty the application keep running smoothly.
> 
> Signed-off-by: Jeff Guo <jia.guo@intel.com>
> ---
> v19->18:
> add note for limitation of multiple hotplug
> ---
>  doc/guides/rel_notes/release_18_05.rst  |   6 ++
>  kernel/linux/igb_uio/igb_uio.c          |   4 +
>  lib/librte_eal/common/include/rte_dev.h |  19 +++++
>  lib/librte_eal/linuxapp/eal/eal_dev.c   | 140
> +++++++++++++++++++++++++++++++-
>  lib/librte_eal/rte_eal_version.map      |   1 +
>  5 files changed, 169 insertions(+), 1 deletion(-)
> 
> diff --git a/doc/guides/rel_notes/release_18_05.rst
> b/doc/guides/rel_notes/release_18_05.rst
> index cb9e050..2707e73 100644
> --- a/doc/guides/rel_notes/release_18_05.rst
> +++ b/doc/guides/rel_notes/release_18_05.rst
> @@ -70,6 +70,12 @@ New Features
> 
>    Linux uevent is supported as backend of this device event notification
> framework.
> 
> +* **Added hot plug failure handler.**
> +
> +  Added a failure handler machenism to handle hot unplug device.
> +
> +  * ``rte_dev_handle_hot_unplug`` for handle hot unplug device failure.
> +
>  API Changes
>  -----------
> 
> diff --git a/kernel/linux/igb_uio/igb_uio.c b/kernel/linux/igb_uio/igb_uio.c
> index 4cae4dd..293c310 100644
> --- a/kernel/linux/igb_uio/igb_uio.c
> +++ b/kernel/linux/igb_uio/igb_uio.c
> @@ -344,6 +344,10 @@ igbuio_pci_release(struct uio_info *info, struct inode
> *inode)
>  	struct rte_uio_pci_dev *udev = info->priv;
>  	struct pci_dev *dev = udev->pdev;
> 
> +	/* check if device has been remove before release */
> +	if ((&dev->dev.kobj)->state_remove_uevent_sent == 1)
> +		return -1;
> +
>  	mutex_lock(&udev->lock);
>  	if (--udev->refcnt > 0) {
>  		mutex_unlock(&udev->lock);
> diff --git a/lib/librte_eal/common/include/rte_dev.h
> b/lib/librte_eal/common/include/rte_dev.h
> index a5203e7..17c446d 100644
> --- a/lib/librte_eal/common/include/rte_dev.h
> +++ b/lib/librte_eal/common/include/rte_dev.h
> @@ -361,4 +361,23 @@ 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
> + *
> + * It can be used to register the device signal bus handler, and save
> +the
> + * current environment for each thread, when signal bus error invoke,
> +the
> + * handler would restore the environment by long jmp to each working
> + * thread previous locate, then block the thread to waiting until the
> +memory
> + * recovery and remapping be finished, that would guaranty the system
> +not
> + * crash when the device be hot unplug.
> + *
> + * @param none
> + * @return
> + *   - From a successful direct invocation, zero.
> + *   - From a call of siglongjmp(), non_zero.
> + */
> +int __rte_experimental
> +rte_dev_handle_hot_unplug(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 9478a39..84b7efc 100644
> --- a/lib/librte_eal/linuxapp/eal/eal_dev.c
> +++ b/lib/librte_eal/linuxapp/eal/eal_dev.c
> @@ -4,6 +4,9 @@
> 
>  #include <string.h>
>  #include <unistd.h>
> +#include <signal.h>
> +#include <setjmp.h>
> +#include <pthread.h>
>  #include <sys/socket.h>
>  #include <linux/netlink.h>
> 
> @@ -13,12 +16,17 @@
>  #include <rte_malloc.h>
>  #include <rte_interrupts.h>
>  #include <rte_alarm.h>
> +#include <rte_bus.h>
> +#include <rte_per_lcore.h>
> 
>  #include "eal_private.h"
> 
>  static struct rte_intr_handle intr_handle = {.fd = -1 };  static bool
> monitor_started;
> 
> +pthread_mutex_t failure_recovery_lock;
> +pthread_cond_t failure_recovery_cond;
> +
>  #define EAL_UEV_MSG_LEN 4096
>  #define EAL_UEV_MSG_ELEM_LEN 128
> 
> @@ -32,6 +40,22 @@ enum eal_dev_event_subsystem {
>  	EAL_DEV_EVENT_SUBSYSTEM_MAX
>  };
> 
> +static RTE_DEFINE_PER_LCORE(sigjmp_buf, unplug_longjmp_env);
> +
> +static void sigbus_handler(int signum __rte_unused) {
> +	RTE_LOG(DEBUG, EAL, "receive SIGBUS error!\n");
> +	siglongjmp(RTE_PER_LCORE(unplug_longjmp_env), 1); }
> +
> +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)
>  {
> @@ -132,6 +156,31 @@ dev_uev_parse(const char *buf, struct rte_dev_event
> *event, int length)
>  	return 0;
>  }
> 
> +static int
> +dev_uev_remove_handler(struct rte_device *dev) {
> +	struct rte_bus *bus = rte_bus_find_by_device_name(dev->name);
> +	int ret;
> +
> +	if (!dev)
> +		return -1;
> +
> +	if (bus->handle_hot_unplug) {
> +		/**
> +		 * call bus ops to handle hot unplug.
> +		 */
> +		ret = bus->handle_hot_unplug(dev);
> +		if (ret) {
> +			RTE_LOG(ERR, EAL,
> +				"It cannot handle hot unplug for device (%s) "
> +				"on the bus.\n ",
> +				dev->name);
> +			return ret;
> +		}
> +	}
> +	return 0;
> +}
> +
>  static void
>  dev_delayed_unregister(void *param)
>  {
> @@ -146,6 +195,9 @@ 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);
> @@ -170,11 +222,87 @@ 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) {
> +			bus = rte_bus_find_by_name(busname);
> +			if (bus == NULL) {
> +				RTE_LOG(ERR, EAL, "Cannot find bus (%s)\n",
> +					uevent.devname);
> +				return;
> +			}
> +			dev = bus->find_device(NULL, cmp_dev_name,
> +					       uevent.devname);
> +			if (dev == NULL) {
> +				RTE_LOG(ERR, EAL,
> +					"Cannot find unplugged device (%s)\n",
> +					uevent.devname);
> +				return;
> +			}
> +			ret = dev_uev_remove_handler(dev);
> +			if (ret) {
> +				RTE_LOG(ERR, EAL, "Driver cannot remap the "
> +					"device (%s)\n",
> +					dev->name);
> +				return;
> +			}
> +			/* wake up all the threads */
> +			pthread_cond_broadcast(&failure_recovery_cond);
> +		}
>  		dev_callback_process(uevent.devname, uevent.type);
> +	}
>  }
> 
>  int __rte_experimental
> +rte_dev_handle_hot_unplug(void)
> +{
> +	struct sigaction act;
> +	sigset_t mask;
> +	int ret = 0;
> +
> +	/* set signal handlers */
> +	memset(&act, 0x00, sizeof(struct sigaction));
> +	act.sa_handler = sigbus_handler;
> +	sigemptyset(&act.sa_mask);
> +	act.sa_flags = SA_RESTART;
> +	sigaction(SIGBUS, &act, NULL);
> +	sigemptyset(&mask);
> +	sigaddset(&mask, SIGBUS);
> +	pthread_sigmask(SIG_UNBLOCK, &mask, NULL);
> +
> +	ret = sigsetjmp(RTE_PER_LCORE(unplug_longjmp_env), 1);
> +	if (ret) {
> +		/*
> +		 * Waitting for condition variable before failure recovery
> +		 * finish. Now the limitation is only handle one device
> +		 * hot plug, for multiple devices hotplug, need check if
> +		 * the device belong to this working thread, then directly
> +		 * call memory remaping, unrelated thread just keep going
> +		 * their work by no interrupt from hotplug.
> +		 * TODO: multiple device hotplug
> +		 */
> +		pthread_mutex_lock(&failure_recovery_lock);
> +		RTE_LOG(DEBUG, EAL, "begin waiting for the failure handler.\n");
> +		pthread_cond_wait(&failure_recovery_cond,
> +					&failure_recovery_lock);
> +		RTE_LOG(DEBUG, EAL,
> +		       "come back from waiting for failure handler.\n");
> +		pthread_mutex_unlock(&failure_recovery_lock);

I think we should not assume phread_cond_wait always happen before pthread_cond_broadcast,
It is possible Sigbus just happen before remap in udev remove handler while pthread_cond_wait happens
after pthread_cond_broadcast, then we will wait forever.

I think we need a flag to sync
For example:

pthread_mutex_lock(&failure_recovery_lock);
if ( udev_remove_handle == 0 )
	pthread_cond_wait(&failure_recovery_cond, & failure_recovery_lock);
pthread_remove_handle = 0;
pthread_mutex_unlock(&failure_recovery_lock);

while at remove handler:
pthread_mutex_lock(&failure_recovery_lock);
pthread_remove_handle = 1;
pthread_cond_signel(&failure_recovery_cond);
pthread_mutex_unlock(&failure_recovery_lock);


Regards
Qi

> +	}
> +
> +	return ret;
> +}
> +
> +
> +int __rte_experimental
>  rte_dev_event_monitor_start(void)
>  {
>  	int ret;
> @@ -196,6 +324,12 @@ rte_dev_event_monitor_start(void)
>  		return -1;
>  	}
> 
> +	/* initialize mutex and condition variable
> +	 * to control failure recovery.
> +	 */
> +	pthread_mutex_init(&failure_recovery_lock, NULL);
> +	pthread_cond_init(&failure_recovery_cond, NULL);
> +
>  	monitor_started = true;
> 
>  	return 0;
> @@ -219,5 +353,9 @@ rte_dev_event_monitor_stop(void)
>  	close(intr_handle.fd);
>  	intr_handle.fd = -1;
>  	monitor_started = false;
> +
> +	pthread_cond_destroy(&failure_recovery_cond);
> +	pthread_mutex_destroy(&failure_recovery_lock);
> +
>  	return 0;
>  }
> diff --git a/lib/librte_eal/rte_eal_version.map
> b/lib/librte_eal/rte_eal_version.map
> index fc5c62a..873ef38 100644
> --- a/lib/librte_eal/rte_eal_version.map
> +++ b/lib/librte_eal/rte_eal_version.map
> @@ -262,5 +262,6 @@ EXPERIMENTAL {
>  	rte_dev_event_monitor_stop;
>  	rte_dev_event_callback_register;
>  	rte_dev_event_callback_unregister;
> +	rte_dev_handle_hot_unplug;
> 
>  } DPDK_18.02;
> --
> 2.7.4