One more comment
> -----Original Message-----
> From: dev [mailto:dev-boun...@dpdk.org] On Behalf Of Zhang, Qi Z
> Sent: Friday, April 6, 2018 10:04 PM
> To: Guo, Jia <jia....@intel.com>; step...@networkplumber.org; Richardson,
> Bruce <bruce.richard...@intel.com>; Yigit, Ferruh <ferruh.yi...@intel.com>;
> Ananyev, Konstantin <konstantin.anan...@intel.com>;
> gaetan.ri...@6wind.com; Wu, Jingjing <jingjing...@intel.com>;
> tho...@monjalon.net; mo...@mellanox.com; Van Haaren, Harry
> <harry.van.haa...@intel.com>; Tan, Jianfeng <jianfeng....@intel.com>
> Cc: jblu...@infradead.org; shreyansh.j...@nxp.com; dev@dpdk.org; Guo, Jia
> <jia....@intel.com>; Zhang, Helin <helin.zh...@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-boun...@dpdk.org] On Behalf Of Jeff Guo
> > Sent: Friday, April 6, 2018 6:57 PM
> > To: step...@networkplumber.org; Richardson, Bruce
> > <bruce.richard...@intel.com>; Yigit, Ferruh <ferruh.yi...@intel.com>;
> > Ananyev, Konstantin <konstantin.anan...@intel.com>;
> > gaetan.ri...@6wind.com; Wu, Jingjing <jingjing...@intel.com>;
> > tho...@monjalon.net; mo...@mellanox.com; Van Haaren, Harry
> > <harry.van.haa...@intel.com>; Tan, Jianfeng <jianfeng....@intel.com>
> > Cc: jblu...@infradead.org; shreyansh.j...@nxp.com; dev@dpdk.org; Guo,
> > Jia <jia....@intel.com>; Zhang, Helin <helin.zh...@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.
> 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....@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
