Provided by: libfabric-dev_1.6.2-3ubuntu0.1_amd64 bug

NAME

       fi_poll - Polling and wait set operations

       fi_poll_open / fi_close : Open/close a polling set

       fi_poll_add / fi_poll_del : Add/remove a completion queue or counter to/from a poll set.

       fi_poll : Poll for progress and events across multiple completion queues and counters.

       fi_wait_open / fi_close : Open/close a wait set

       fi_wait : Waits for one or more wait objects in a set to be signaled.

       fi_trywait : Indicate when it is safe to block on wait objects using native OS calls.

       fi_control : Control wait set operation or attributes.

SYNOPSIS

              #include <rdma/fi_domain.h>

              int fi_poll_open(struct fid_domain *domain, struct fi_poll_attr *attr,
                  struct fid_poll **pollset);

              int fi_close(struct fid *pollset);

              int fi_poll_add(struct fid_poll *pollset, struct fid *event_fid,
                  uint64_t flags);

              int fi_poll_del(struct fid_poll *pollset, struct fid *event_fid,
                  uint64_t flags);

              int fi_poll(struct fid_poll *pollset, void **context, int count);

              int fi_wait_open(struct fid_fabric *fabric, struct fi_wait_attr *attr,
                  struct fid_wait **waitset);

              int fi_close(struct fid *waitset);

              int fi_wait(struct fid_wait *waitset, int timeout);

              int fi_trywait(struct fid_fabric *fabric, struct fid **fids, size_t count);

              int fi_control(struct fid *waitset, int command, void *arg);

ARGUMENTS

       fabric : Fabric provider

       domain : Resource domain

       pollset : Event poll set

       waitset : Wait object set

       attr : Poll or wait set attributes

       context : On success, an array of user context values associated with completion queues or
       counters.

       fids : An array of fabric descriptors, each one associated with a native wait object.

       count : Number of entries in context or fids array.

       timeout : Time to wait for a signal, in milliseconds.

       command : Command of control operation to perform on the wait set.

       arg : Optional control argument.

DESCRIPTION

   fi_poll_open
       fi_poll_open creates a new polling set.  A  poll  set  enables  an  optimized  method  for
       progressing  asynchronous  operations  across  multiple completion queues and counters and
       checking for their completions.

       A poll set is defined with the following attributes.

              struct fi_poll_attr {
                  uint64_t             flags;     /* operation flags */
              };

       flags : Flags that set the default operation of the poll set.  The use of  this  field  is
       reserved and must be set to 0 by the caller.

   fi_close
       The  fi_close  call  releases all resources associated with a poll set.  The poll set must
       not be associated with any other resources prior to being closed, otherwise the call  will
       return -FI_EBUSY.

   fi_poll_add
       Associates a completion queue or counter with a poll set.

   fi_poll_del
       Removes a completion queue or counter from a poll set.

   fi_poll
       Progresses  all  completion  queues and counters associated with a poll set and checks for
       events.  If events might have occurred, contexts associated  with  the  completion  queues
       and/or counters are returned.  Completion queues will return their context if they are not
       empty.  The context associated with a counter will be returned if  the  counter's  success
       value or error value have changed since the last time fi_poll, fi_cntr_set, or fi_cntr_add
       were called.  The number of contexts  is  limited  to  the  size  of  the  context  array,
       indicated by the count parameter.

       Note that fi_poll only indicates that events might be available.  In some cases, providers
       may consume such events internally, to drive progress, for example.  This  can  result  in
       fi_poll  returning false positives.  Applications should drive their progress based on the
       results of reading events from a completion queue or reading counter values.  The  fi_poll
       function will always return all completion queues and counters that do have new events.

   fi_wait_open
       fi_wait_open  allocates a new wait set.  A wait set enables an optimized method of waiting
       for events across multiple completion queues and counters.  Where  possible,  a  wait  set
       uses a single underlying wait object that is signaled when a specified condition occurs on
       an associated completion queue or counter.

       The properties and behavior of a wait set are defined by struct fi_wait_attr.

              struct fi_wait_attr {
                  enum fi_wait_obj     wait_obj;  /* requested wait object */
                  uint64_t             flags;     /* operation flags */
              };

       wait_obj : Wait sets are associated with specific  wait  object(s).   Wait  objects  allow
       applications  to  block  until  the  wait  object is signaled, indicating that an event is
       available to be read.  The following values may be used to specify the type of wait object
       associated with a wait set: FI_WAIT_UNSPEC, FI_WAIT_FD, and FI_WAIT_MUTEX_COND.

       • FI_WAIT_UNSPEC  :  Specifies  that  the user will only wait on the wait set using fabric
         interface calls, such as fi_wait.  In this case, the underlying provider may select  the
         most  appropriate  or  highest  performing  wait object available, including custom wait
         mechanisms.  Applications that select FI_WAIT_UNSPEC are not guaranteed to retrieve  the
         underlying wait object.

       • FI_WAIT_FD  :  Indicates  that  the  wait  set should use file descriptor(s) as its wait
         mechanism.  It may not always be possible for a wait  set  to  be  implemented  using  a
         single  underlying file descriptor, but all wait objects will be file descriptors.  File
         descriptor wait objects must be usable in the POSIX  select(2),  poll(2),  and  epoll(7)
         routines (if available).  However, a provider may signal an FD wait object by marking it
         as readable or with an error.

       • FI_WAIT_MUTEX_COND : Specifies that the wait set should use a  pthread  mutex  and  cond
         variable as a wait object.

       • FI_WAIT_CRITSEC_COND  :  Windows  specific.  Specifies that the EQ should use a critical
         section and condition variable as a wait object.

       flags : Flags that set the default operation of the wait set.  The use of  this  field  is
       reserved and must be set to 0 by the caller.

   fi_close
       The  fi_close  call  releases all resources associated with a wait set.  The wait set must
       not be bound to any other opened resources prior to being closed, otherwise the call  will
       return -FI_EBUSY.

   fi_wait
       Waits on a wait set until one or more of its underlying wait objects is signaled.

   fi_trywait
       The fi_trywait call was introduced in libfabric version 1.3.  The behavior of using native
       wait objects without the use of fi_trywait is provider specific and should  be  considered
       non-deterministic.

       The  fi_trywait()  call is used in conjunction with native operating system calls to block
       on wait objects, such as file descriptors.   The  application  must  call  fi_trywait  and
       obtain a return value of FI_SUCCESS prior to blocking on a native wait object.  Failure to
       do so may result in the wait object not being signaled, and the application not  observing
       the  desired  events.   The  following  pseudo-code  demonstrates the use of fi_trywait in
       conjunction with the OS select(2) call.

              fi_control(&cq->fid, FI_GETWAIT, (void *) &fd);
              FD_ZERO(&fds);
              FD_SET(fd, &fds);

              while (1) {
                  if (fi_trywait(&cq, 1) == FI_SUCCESS)
                      select(fd + 1, &fds, NULL, &fds, &timeout);

                  do {
                      ret = fi_cq_read(cq, &comp, 1);
                  } while (ret > 0);
              }

       fi_trywait() will return FI_SUCCESS  if  it  is  safe  to  block  on  the  wait  object(s)
       corresponding to the fabric descriptor(s), or -FI_EAGAIN if there are events queued on the
       fabric descriptor or if blocking could hang the application.

       The call takes an array of fabric descriptors.  For each wait object that will  be  passed
       to  the native wait routine, the corresponding fabric descriptor should first be passed to
       fi_trywait.  All fabric descriptors passed into a single fi_trywait call must make use  of
       the same underlying wait object type.

       The  following  types  of  fabric descriptors may be passed into fi_trywait: event queues,
       completion queues, counters, and wait sets.  Applications that wish  to  use  native  wait
       calls should select specific wait objects when allocating such resources.  For example, by
       setting the item's creation attribute wait_obj value to FI_WAIT_FD.

       In the case the wait object to check belongs to a wait set, only the wait set itself needs
       to be passed into fi_trywait.  The fabric resources associated with the wait set do not.

       On  receiving a return value of -FI_EAGAIN from fi_trywait, an application should read all
       queued completions and events, and call  fi_trywait  again  before  attempting  to  block.
       Applications  can make use of a fabric poll set to identify completion queues and counters
       that may require processing.

   fi_control
       The fi_control call is used to access provider or implementation specific details  of  the
       wait set.  Access to the wait set should be serialized across all calls when fi_control is
       invoked, as it may redirect the implementation of  wait  set  operations.   The  following
       control commands are usable with a wait set.

       FI_GETWAIT  (void **) : This command allows the user to retrieve the low-level wait object
       associated with the wait set.  The format of the wait set is  specified  during  wait  set
       creation,  through  the  wait  set  attributes.  The fi_control arg parameter should be an
       address where a pointer to the returned wait object will be written.  This  should  be  an
       'int  *'  for  FI_WAIT_FD,  or 'struct fi_mutex_cond' for FI_WAIT_MUTEX_COND.  Support for
       FI_GETWAIT is provider specific and may fail if not  supported  or  if  the  wait  set  is
       implemented using more than one wait object.

RETURN VALUES

       Returns  FI_SUCCESS  on success.  On error, a negative value corresponding to fabric errno
       is returned.

       Fabric errno values are defined in rdma/fi_errno.h.

       fi_poll : On success, if events are available, returns the number of  entries  written  to
       the context array.

NOTES

SEE ALSO

       fi_getinfo(3), fi_domain(3), fi_cntr(3), fi_eq(3)

AUTHORS

       OpenFabrics.