[ViewVC] Diff of: cvs/libev/ev

Comparing libev/ev_linuxaio.c (file contents):
Revision 1.32 by root, Tue Jun 25 18:07:44 2019 UTC vs.
Revision 1.39 by root, Mon Jul 1 20:34:31 2019 UTC

  * not only is this totally undocumented, not even the source code
  * can tell you what the future semantics of compat_features and
  * incompat_features are, or what header_length actually is for.
  */
 #define AIO_RING_MAGIC                  0xa10a10a1
-#define AIO_RING_INCOMPAT_FEATURES      0
+#define EV_AIO_RING_INCOMPAT_FEATURES   0
 struct aio_ring
 {
   unsigned id;    /* kernel internal index number */
   unsigned nr;    /* number of io_events */
   unsigned head;  /* Written to by userland or by kernel. */
   ANIOCBP iocb = linuxaio_iocbps [fd];
   if (iocb->io.aio_reqprio < 0)
     {
       /* we handed this fd over to epoll, so undo this first */
-      /* we do it manually because the optimisations on epoll_modfy won't do us any good */
+      /* we do it manually because the optimisations on epoll_modify won't do us any good */
       epoll_ctl (backend_fd, EPOLL_CTL_DEL, fd, 0);
       anfds [fd].emask = 0;
       iocb->io.aio_reqprio = 0;
     }
   if (iocb->io.aio_buf)
-    /* io_cancel always returns some error on relevant kernels, but works */
+    {
+      for (;;)
+        {
+          /* on all relevant kernels, io_cancel fails with EINPROGRESS on "success" */
-    evsys_io_cancel (linuxaio_ctx, &iocb->io, (struct io_event *)0);
+          if (expect_false (evsys_io_cancel (linuxaio_ctx, &iocb->io, (struct io_event *)0) == 09)
+            break;
+          if (expect_true (errno == EINPROGRESS))
+            break;
+          /* the EINPROGRESS test is for nicer error message. clumsy. */
+          assert (("libev: linuxaio unexpected io_cancel failed", errno != EINPROGRESS && errno != EINTR));
+       }
+    }
   if (nev)
     {
       iocb->io.aio_buf =
           (nev & EV_READ ? POLLIN : 0)
 linuxaio_epoll_cb (EV_P_ struct ev_io *w, int revents)
 {
   epoll_poll (EV_A_ 0);
 }
-static void
+inline_speed
+void
 linuxaio_fd_rearm (EV_P_ int fd)
 {
   anfds [fd].events = 0;
   linuxaio_iocbps [fd]->io.aio_buf = 0;
   fd_change (EV_A_ fd, EV_ANFD_REIFY);
         fd,
         (res & (POLLOUT | POLLERR | POLLHUP) ? EV_WRITE : 0)
         | (res & (POLLIN | POLLERR | POLLHUP) ? EV_READ : 0)
       );
-      /* linux aio is oneshot: rearm fd. TODO: this does more work than needed */
+      /* linux aio is oneshot: rearm fd. TODO: this does more work than strictly needed */
       linuxaio_fd_rearm (EV_A_ fd);
       --nr;
       ++ev;
     }
   unsigned tail = *(volatile unsigned *)&ring->tail;
   if (head == tail)
     return 0;
-  /* bail out if the ring buffer doesn't match the expected layout */
-  if (expect_false (ring->magic != AIO_RING_MAGIC)
-                    || ring->incompat_features != AIO_RING_INCOMPAT_FEATURES
-                    || ring->header_length != sizeof (struct aio_ring)) /* TODO: or use it to find io_event[0]? */
-    return 0;
   /* make sure the events up to tail are visible */
   ECB_MEMORY_FENCE_ACQUIRE;
   /* parse all available events, but only once, to avoid starvation */
   if (tail > head) /* normal case around */
   *(volatile unsigned *)&ring->head = tail;
   return 1;
 }
+inline_size
+int
+linuxaio_ringbuf_valid (EV_P)
+{
+  struct aio_ring *ring = (struct aio_ring *)linuxaio_ctx;
+  return expect_true (ring->magic == AIO_RING_MAGIC)
+                      && ring->incompat_features == EV_AIO_RING_INCOMPAT_FEATURES
+                      && ring->header_length == sizeof (struct aio_ring); /* TODO: or use it to find io_event[0]? */
+}
 /* read at least one event from kernel, or timeout */
 inline_size
 void
 linuxaio_get_events (EV_P_ ev_tstamp timeout)
 {
   struct timespec ts;
-  struct io_event ioev[1];
+  struct io_event ioev[8]; /* 256 octet stack space */
-  int res;
+  int want = 1; /* how many events to request */
+  int ringbuf_valid = linuxaio_ringbuf_valid (EV_A);
+  if (expect_true (ringbuf_valid))
+    {
+      /* if the ring buffer has any events, we don't wait or call the kernel at all */
-  if (linuxaio_get_events_from_ring (EV_A))
+      if (linuxaio_get_events_from_ring (EV_A))
-    return;
+        return;
-  /* no events, so wait for at least one, then poll ring buffer again */
+      /* if the ring buffer is empty, and we don't have a timeout, then don't call the kernel */
-  /* this degrades to one event per loop iteration */
+      if (!timeout)
-  /* if the ring buffer changes layout, but so be it */
+        return;
+    }
+  else
+    /* no ringbuffer, request slightly larger batch */
+    want = sizeof (ioev) / sizeof (ioev [0]);
+  /* no events, so wait for some
+   * for fairness reasons, we do this in a loop, to fetch all events
+   */
+  for (;;)
+    {
+      int res;
-  EV_RELEASE_CB;
+      EV_RELEASE_CB;
-  ts.tv_sec  = (long)timeout;
+      ts.tv_sec  = (long)timeout;
-  ts.tv_nsec = (long)((timeout - ts.tv_sec) * 1e9);
+      ts.tv_nsec = (long)((timeout - ts.tv_sec) * 1e9);
-  res = evsys_io_getevents (linuxaio_ctx, 1, sizeof (ioev) / sizeof (ioev [0]), ioev, &ts);
+      res = evsys_io_getevents (linuxaio_ctx, 1, want, ioev, &ts);
-  EV_ACQUIRE_CB;
+      EV_ACQUIRE_CB;
-  if (res < 0)
+      if (res < 0)
-    if (errno == EINTR)
+        if (errno == EINTR)
-      /* ignored */;
+          /* ignored, retry */;
-    else
+        else
-      ev_syserr ("(libev) linuxaio io_getevents");
+          ev_syserr ("(libev) linuxaio io_getevents");
-  else if (res)
+      else if (res)
-    {
+        {
-      /* at least one event available, handle it and any remaining ones in the ring buffer */
+          /* at least one event available, handle them */
-      linuxaio_parse_events (EV_A_ ioev, res);
+          linuxaio_parse_events (EV_A_ ioev, res);
+          if (expect_true (ringbuf_valid))
+            {
+              /* if we have a ring buffer, handle any remaining events in it */
-      linuxaio_get_events_from_ring (EV_A);
+              linuxaio_get_events_from_ring (EV_A);
+              /* at this point, we should have handled all outstanding events */
+              break;
+            }
+          else if (res < want)
+            /* otherwise, if there were fewere events than we wanted, we assume there are no more */
+            break;
+        }
+      else
+        break; /* no events from the kernel, we are done */
+      timeout = 0; /* only wait in the first iteration */
     }
 }
 inline_size
 int
             /* it's easiest to handle this mess in another iteration */
             return;
           }
         else if (errno == EBADF)
           {
+            assert (("libev: event loop rejected bad fd", errno != EBADF));
             fd_kill (EV_A_ linuxaio_submits [submitted]->aio_fildes);
             res = 1; /* skip this iocb */
           }
+        else if (errno == EINTR) /* not seen in reality, not documented */
+          res = 0; /* silently ignore and retry */
         else
           ev_syserr ("(libev) linuxaio io_submit");
       submitted += res;
     }
 void
 linuxaio_destroy (EV_P)
 {
   epoll_destroy (EV_A);
   linuxaio_free_iocbp (EV_A);
-  evsys_io_destroy (linuxaio_ctx);
+  evsys_io_destroy (linuxaio_ctx); /* fails in child, aio context is destroyed */
 }
 inline_size
 void
 linuxaio_fork (EV_P)
   linuxaio_iteration = 0; /* we start over in the child */
   while (linuxaio_io_setup (EV_A) < 0)
     ev_syserr ("(libev) linuxaio io_setup");
+  /* forking epoll should also effectively unregister all fds from the backend */
   epoll_fork (EV_A);
   ev_io_stop  (EV_A_ &linuxaio_epoll_w);
   ev_io_set   (EV_A_ &linuxaio_epoll_w, backend_fd, EV_READ);
   ev_io_start (EV_A_ &linuxaio_epoll_w);

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Comparing libev/ev_linuxaio.c (file contents): Revision 1.32 by root, Tue Jun 25 18:07:44 2019 UTC vs. Revision 1.39 by root, Mon Jul 1 20:34:31 2019 UTC

Diff Legend

Comparing libev/ev_linuxaio.c (file contents):
Revision 1.32 by root, Tue Jun 25 18:07:44 2019 UTC vs.
Revision 1.39 by root, Mon Jul 1 20:34:31 2019 UTC