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

["Guo, Jia" <jia.guo@intel.com>]

On 4/6/2018 10:24 PM, Zhang, Qi Z wrote:
> One more comment
>
>> -----Original Message-----
>> From: dev [mailto:dev-bounces@dpdk.org] On Behalf Of Zhang, Qi Z
>> Sent: Friday, April 6, 2018 10:04 PM
>> To: Guo, Jia <jia.guo@intel.com>; 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: Re: [dpdk-dev] [PATCH V19 2/4] eal: add failure handler mechanism
>> for hot plug
>>
>> 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,
> The description is a little bit misleading , based on current implementation.
> it does not a function that let user "register a handler", actually It let user to
> "set a recover point" when some exception (like sigbus) happen due to hot unplug.
> Maybe the function name could be changed also,
> for example: rte_dev_set_recover_point.
make sense , will check the better way demonstrate that.
>> 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