Re: [dpdk-dev] [PATCH V18 3/5] eal: add failure handler mechanism for hot plug

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

On 4/4/2018 10:58 AM, Zhang, Qi Z wrote:
>
>> -----Original Message-----
>> From: dev [mailto:dev-bounces@dpdk.org] On Behalf Of Jeff Guo
>> Sent: Wednesday, April 4, 2018 2:17 AM
>> 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 V18 3/5] 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>
>> ---
>> v16->v15:
>> add document and signal bus handler
>> ---
>>   doc/guides/rel_notes/release_18_05.rst    |   6 ++
>>   lib/librte_eal/common/include/rte_dev.h   |  19 +++++
>>   lib/librte_eal/linuxapp/eal/eal_dev.c     | 134
>> +++++++++++++++++++++++++++++-
>>   lib/librte_eal/linuxapp/igb_uio/igb_uio.c |   4 +
>>   lib/librte_eal/rte_eal_version.map        |   1 +
>>   5 files changed, 163 insertions(+), 1 deletion(-)
>>
>> diff --git a/doc/guides/rel_notes/release_18_05.rst
>> b/doc/guides/rel_notes/release_18_05.rst
>> index 37e00c4..3aacbf1 100644
>> --- a/doc/guides/rel_notes/release_18_05.rst
>> +++ b/doc/guides/rel_notes/release_18_05.rst
>> @@ -51,6 +51,12 @@ New Features
>>     * ``rte_dev_event_callback_register`` and
>> ``rte_dev_event_callback_unregister``
>>       are for the user's callbacks register and unregister.
>>
>> +* **Added hot plug failure handler.**
>> +
>> +  Added a failure handler machenism to handle hot plug removal.
>> +
>> +  * ``rte_dev_handle_hot_unplug`` for handle hot plug removel failure.
>> +
>>   API Changes
>>   -----------
>>
>> diff --git a/lib/librte_eal/common/include/rte_dev.h
>> b/lib/librte_eal/common/include/rte_dev.h
>> index 4c78938..7075e56 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 of each thread, when signal bus error invoke,
>> +the
>> + * handler would restore the environment by long jmp to each working
>> + * thread, 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
>> + *   - On success, zero.
>> + *   - On failure, a negative value.
>> + */
>> +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 9f2ee40..fabb37a 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>
>>
>> @@ -12,12 +15,17 @@
>>   #include <rte_dev.h>
>>   #include <rte_malloc.h>
>>   #include <rte_interrupts.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
>>
>> @@ -29,6 +37,22 @@ 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)
>>   {
>> @@ -135,16 +159,114 @@ dev_uev_receive(int fd, struct rte_dev_event
>> *uevent)
>>   	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_uev_process(__rte_unused void *param)  {
>>   	struct rte_dev_event uevent;
>> +	struct rte_bus *bus;
>> +	struct rte_device *dev;
>> +	const char *busname;
>> +	int ret = 0;
>>
>>   	if (dev_uev_receive(intr_handle.fd, &uevent))
>>   		return;
>>
>> -	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;
>> +
>> +	/* 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);
>> +
>> +	if (sigsetjmp(RTE_PER_LCORE(unplug_longjmp_env), 1)) {
>> +		/*
>> +		 * wait on condition variable
>> +		 * before failure recovery be finish.
>> +		 */
>> +		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);
>> +	}
>> +
>> +	return 0;
> Should we return the value of sigsetjmp, so application can know "rewind" happened and can do some clean up?
good idea. please check next version.
>>   }
>>
>>   int __rte_experimental
>> @@ -169,6 +291,12 @@ 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;
>> @@ -192,5 +320,9 @@ 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/linuxapp/igb_uio/igb_uio.c
>> b/lib/librte_eal/linuxapp/igb_uio/igb_uio.c
>> index 4cae4dd..293c310 100644
>> --- a/lib/librte_eal/linuxapp/igb_uio/igb_uio.c
>> +++ b/lib/librte_eal/linuxapp/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/rte_eal_version.map
>> b/lib/librte_eal/rte_eal_version.map
>> index d23f491..d37dd29 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_callback_register;
>>           rte_dev_event_callback_unregister;
>> +	rte_dev_handle_hot_unplug;
>>
>>   } DPDK_18.05;
>> --
>> 2.7.4