X-Git-Url: http://mj.ucw.cz/gitweb/?a=blobdiff_plain;ds=sidebyside;f=ucw%2Fmainloop.c;h=b2b07c5082476bedbdc023e094f49f6feb02a28b;hb=6efdc514c193f18c9ef840096750c37e78a01bf6;hp=7b5d504506d9c09ee54d07d661cdbf940c63f3af;hpb=afcc58361781c05d66fe37ea2bccd53edf8f7aa5;p=libucw.git

diff --git a/ucw/mainloop.c b/ucw/mainloop.c
index 7b5d5045..b2b07c50 100644
--- a/ucw/mainloop.c
+++ b/ucw/mainloop.c
@@ -1,7 +1,7 @@
 /*
  *	UCW Library -- Main Loop
  *
- *	(c) 2004--2010 Martin Mares <mj@ucw.cz>
+ *	(c) 2004--2012 Martin Mares <mj@ucw.cz>
  *
  *	This software may be freely distributed and used according to the terms
  *	of the GNU Lesser General Public License.
@@ -9,11 +9,13 @@
 
 #undef LOCAL_DEBUG
 
-#include "ucw/lib.h"
-#include "ucw/heap.h"
-#include "ucw/mainloop.h"
-#include "ucw/threads.h"
-#include "ucw/gary.h"
+#include <ucw/lib.h>
+#include <ucw/heap.h>
+#include <ucw/mainloop.h>
+#include <ucw/threads.h>
+#include <ucw/gary.h>
+#include <ucw/process.h>
+#include <ucw/time.h>
 
 #include <stdio.h>
 #include <string.h>
@@ -34,16 +36,51 @@
 #define THREAD_SIGMASK sigprocmask
 #endif
 
+#ifdef CONFIG_UCW_EPOLL
+#include <sys/epoll.h>
+#endif
+
 #define MAIN_TIMER_LESS(x,y) ((x)->expires < (y)->expires)
 #define MAIN_TIMER_SWAP(heap,a,b,t) (t=heap[a], heap[a]=heap[b], heap[b]=t, heap[a]->index=(a), heap[b]->index=(b))
 
+#define EPOLL_BUF_SIZE 256
+
+static void file_del_ctx(struct main_context *m, struct main_file *fi);
+static void signal_del_ctx(struct main_context *m, struct main_signal *ms);
+
 static void
-do_main_get_time(struct main_context *m)
+main_get_time_ctx(struct main_context *m)
+{
+  m->now = get_timestamp();
+}
+
+static struct main_context *
+main_current_nocheck(void)
+{
+  return ucwlib_thread_context()->main_context;
+}
+
+struct main_context *
+main_current(void)
+{
+  struct main_context *m = main_current_nocheck();
+  ASSERT(m);
+  return m;
+}
+
+static int
+main_is_current(struct main_context *m)
+{
+  return (m == main_current_nocheck());
+}
+
+static inline uns
+count_timers(struct main_context *m)
 {
-  struct timeval tv;
-  gettimeofday(&tv, NULL);
-  m->now_seconds = tv.tv_sec;
-  m->now = (timestamp_t)tv.tv_sec * 1000 + tv.tv_usec / 1000;
+  if (m->timer_table)
+    return GARY_SIZE(m->timer_table) - 1;
+  else
+    return 0;
 }
 
 struct main_context *
@@ -53,40 +90,107 @@ main_new(void)
 
   DBG("MAIN: New context");
   clist_init(&m->file_list);
+  clist_init(&m->file_active_list);
   clist_init(&m->hook_list);
   clist_init(&m->hook_done_list);
   clist_init(&m->process_list);
   clist_init(&m->signal_list);
+#ifdef CONFIG_UCW_EPOLL
+  m->epoll_fd = epoll_create(64);
+  if (m->epoll_fd < 0)
+    die("epoll_create() failed: %m");
+  m->epoll_events = xmalloc(EPOLL_BUF_SIZE * sizeof(struct epoll_event));
+  clist_init(&m->file_recalc_list);
+#else
   m->poll_table_obsolete = 1;
-  do_main_get_time(m);
+#endif
+  main_get_time_ctx(m);
   sigemptyset(&m->want_signals);
   m->sig_pipe_recv = m->sig_pipe_send = -1;
 
   return m;
 }
 
-void
-main_delete(struct main_context *m)
+static void
+main_prepare_delete(struct main_context *m)
 {
+  /*
+   *  If the context is current, deactivate it first. But beware,
+   *  we must not call functions that depend on the current context.
+   */
+  if (main_is_current(m))
+    main_switch_context(NULL);
+
+  // Close epoll descriptor early enough, it might be shared after fork!
+#ifdef CONFIG_UCW_EPOLL
+  xfree(m->epoll_events);
+  close(m->epoll_fd);
+  m->epoll_fd = -1;
+#else
+  GARY_FREE(m->poll_table);
+  GARY_FREE(m->poll_file_table);
+#endif
+
   if (m->sigchld_handler)
-    signal_del(m->sigchld_handler);
+    {
+      signal_del_ctx(m, m->sigchld_handler);
+      xfree(m->sigchld_handler);
+    }
   if (m->sig_pipe_file)
-    file_del(m->sig_pipe_file);
+    {
+      file_del_ctx(m, m->sig_pipe_file);
+      xfree(m->sig_pipe_file);
+     }
   if (m->sig_pipe_recv >= 0)
     {
       close(m->sig_pipe_recv);
       close(m->sig_pipe_send);
     }
+}
+
+static void
+main_do_delete(struct main_context *m)
+{
+  GARY_FREE(m->timer_table);
+  xfree(m);
+}
+
+void
+main_delete(struct main_context *m)
+{
+  if (!m)
+    return;
+
+  main_prepare_delete(m);
   ASSERT(clist_empty(&m->file_list));
+  ASSERT(clist_empty(&m->file_active_list));
+#ifdef CONFIG_UCW_EPOLL
+  ASSERT(clist_empty(&m->file_recalc_list));
+#endif
   ASSERT(clist_empty(&m->hook_list));
   ASSERT(clist_empty(&m->hook_done_list));
   ASSERT(clist_empty(&m->process_list));
   ASSERT(clist_empty(&m->signal_list));
-  if (m->timer_table)
-    GARY_FREE(m->timer_table);
-  xfree(m->poll_table);
-  xfree(m);
-  // FIXME: Some mechanism for cleaning up after fork()
+  ASSERT(!count_timers(m));
+  main_do_delete(m);
+}
+
+void
+main_destroy(struct main_context *m)
+{
+  if (!m)
+    return;
+  main_prepare_delete(m);
+
+  // Close all files
+  clist_insert_list_after(&m->file_active_list, m->file_list.head.prev);
+#ifdef CONFIG_UCW_EPOLL
+  clist_insert_list_after(&m->file_recalc_list, m->file_list.head.prev);
+#endif
+  CLIST_FOR_EACH(struct main_file *, f, m->file_list)
+    close(f->fd);
+
+  main_do_delete(m);
 }
 
 struct main_context *
@@ -109,15 +213,6 @@ main_switch_context(struct main_context *m)
   return m0;
 }
 
-struct main_context *
-main_current(void)
-{
-  struct ucwlib_context *c = ucwlib_thread_context();
-  struct main_context *m = c->main_context;
-  ASSERT(m);
-  return m;
-}
-
 void
 main_init(void)
 {
@@ -128,20 +223,19 @@ main_init(void)
 void
 main_cleanup(void)
 {
-  struct main_context *m = main_switch_context(NULL);
-  main_delete(m);
+  main_delete(main_current_nocheck());
 }
 
 void
-main_get_time(void)
+main_teardown(void)
 {
-  do_main_get_time(main_current());
+  main_destroy(main_current_nocheck());
 }
 
-static inline uns
-count_timers(struct main_context *m)
+void
+main_get_time(void)
 {
-  return GARY_SIZE(m->timer_table) - 1;
+  main_get_time_ctx(main_current());
 }
 
 void
@@ -206,16 +300,37 @@ timer_del(struct main_timer *tm)
   timer_add(tm, 0);
 }
 
+static uns
+file_want_events(struct main_file *fi)
+{
+  uns events = 0;
+  if (fi->read_handler)
+    events |= POLLIN;
+  if (fi->write_handler)
+    events |= POLLOUT;
+  return events;
+}
+
 void
 file_add(struct main_file *fi)
 {
   struct main_context *m = main_current();
 
   DBG("MAIN: Adding file %p (fd=%d)", fi, fi->fd);
-  ASSERT(!fi->n.next);
+  ASSERT(!file_is_active(fi));
   clist_add_tail(&m->file_list, &fi->n);
   m->file_cnt++;
+#ifdef CONFIG_UCW_EPOLL
+  struct epoll_event evt = {
+    .events = file_want_events(fi),
+    .data.ptr = fi,
+  };
+  if (epoll_ctl(m->epoll_fd, EPOLL_CTL_ADD, fi->fd, &evt) < 0)
+    die("epoll_ctl() failed: %m");
+  fi->last_want_events = evt.events;
+#else
   m->poll_table_obsolete = 1;
+#endif
   if (fcntl(fi->fd, F_SETFL, O_NONBLOCK) < 0)
     msg(L_ERROR, "Error setting fd %d to non-blocking mode: %m. Keep fingers crossed.", fi->fd);
 }
@@ -223,37 +338,38 @@ file_add(struct main_file *fi)
 void
 file_chg(struct main_file *fi)
 {
+#ifdef CONFIG_UCW_EPOLL
+  clist_remove(&fi->n);
+  clist_add_tail(&main_current()->file_recalc_list, &fi->n);
+#else
   struct pollfd *p = fi->pollfd;
   if (p)
-    {
-      p->events = 0;
-      if (fi->read_handler)
-	p->events |= POLLIN | POLLHUP | POLLERR;
-      if (fi->write_handler)
-	p->events |= POLLOUT | POLLERR;
-    }
+    p->events = file_want_events(fi);
+#endif
 }
 
-void
-file_del(struct main_file *fi)
+static void
+file_del_ctx(struct main_context *m, struct main_file *fi)
 {
-  struct main_context *m = main_current();
-
+  // XXX: Can be called on a non-current context
   DBG("MAIN: Deleting file %p (fd=%d)", fi, fi->fd);
-  ASSERT(fi->n.next);
-  clist_remove(&fi->n);
+
+  if (!file_is_active(fi))
+    return;
+  clist_unlink(&fi->n);
   m->file_cnt--;
+#ifdef CONFIG_UCW_EPOLL
+  if (m->epoll_fd >= 0 && epoll_ctl(m->epoll_fd, EPOLL_CTL_DEL, fi->fd, NULL) < 0)
+    die("epoll_ctl() failed: %m");
+#else
   m->poll_table_obsolete = 1;
-  fi->n.next = fi->n.prev = NULL;
+#endif
 }
 
 void
-file_close_all(void)
+file_del(struct main_file *fi)
 {
-  struct main_context *m = main_current();
-
-  CLIST_FOR_EACH(struct main_file *, f, m->file_list)
-    close(f->fd);
+  file_del_ctx(main_current(), fi);
 }
 
 void
@@ -262,7 +378,8 @@ hook_add(struct main_hook *ho)
   struct main_context *m = main_current();
 
   DBG("MAIN: Adding hook %p", ho);
-  ASSERT(!ho->n.next);
+  if (hook_is_active(ho))
+    clist_unlink(&ho->n);
   clist_add_tail(&m->hook_list, &ho->n);
 }
 
@@ -270,9 +387,8 @@ void
 hook_del(struct main_hook *ho)
 {
   DBG("MAIN: Deleting hook %p", ho);
-  ASSERT(ho->n.next);
-  clist_remove(&ho->n);
-  ho->n.next = ho->n.prev = NULL;
+  if (hook_is_active(ho))
+    clist_unlink(&ho->n);
 }
 
 static void
@@ -304,7 +420,7 @@ process_add(struct main_process *mp)
   struct main_context *m = main_current();
 
   DBG("MAIN: Adding process %p (pid=%d)", mp, mp->pid);
-  ASSERT(!mp->n.next);
+  ASSERT(!process_is_active(mp));
   ASSERT(mp->handler);
   clist_add_tail(&m->process_list, &mp->n);
   if (!m->sigchld_handler)
@@ -321,9 +437,8 @@ void
 process_del(struct main_process *mp)
 {
   DBG("MAIN: Deleting process %p (pid=%d)", mp, mp->pid);
-  ASSERT(mp->n.next);
-  clist_remove(&mp->n);
-  mp->n.next = NULL;
+  if (process_is_active(mp))
+    clist_unlink(&mp->n);
 }
 
 int
@@ -365,14 +480,21 @@ pipe_read_handler(struct main_file *mf UNUSED)
   ASSERT(n == sizeof(signum));
 
   DBG("MAIN: Sigpipe: received signal %d", signum);
-  struct main_signal *tmp;
-  CLIST_FOR_EACH_DELSAFE(struct main_signal *, sg, m->signal_list, tmp)
-    if (sg->signum == signum)
-      {
-	DBG("MAIN: Sigpipe: invoking handler %p", sg);
-	// FIXME: Can the handler disappear from here?
-	sg->handler(sg);
-      }
+  struct main_signal iter = { .signum = -1 };
+  struct main_signal *sg = clist_head(&m->signal_list);
+  while (sg)
+    {
+      if (sg->signum == signum)
+	{
+	  DBG("MAIN: Sigpipe: invoking handler %p", sg);
+	  clist_insert_after(&iter.n, &sg->n);
+	  sg->handler(sg);
+	  sg = clist_next(&m->signal_list, &iter.n);
+	  clist_remove(&iter.n);
+	}
+      else
+	sg = clist_next(&m->signal_list, &sg->n);
+    }
 
   return 1;
 }
@@ -422,8 +544,9 @@ signal_add(struct main_signal *ms)
 
   DBG("MAIN: Adding signal %p (sig=%d)", ms, ms->signum);
 
-  ASSERT(!ms->n.next);
-  clist_add_tail(&m->signal_list, &ms->n);
+  ASSERT(!signal_is_active(ms));
+  // Adding at the head of the list is better if we are in the middle of walking the list.
+  clist_add_head(&m->signal_list, &ms->n);
   if (m->sig_pipe_recv < 0)
     pipe_setup(m);
 
@@ -440,16 +563,15 @@ signal_add(struct main_signal *ms)
   sigaddset(&m->want_signals, ms->signum);
 }
 
-void
-signal_del(struct main_signal *ms)
+static void
+signal_del_ctx(struct main_context *m, struct main_signal *ms)
 {
-  struct main_context *m = main_current();
-
+  // XXX: Can be called on a non-current context
   DBG("MAIN: Deleting signal %p (sig=%d)", ms, ms->signum);
 
-  ASSERT(ms->n.next);
-  clist_remove(&ms->n);
-  ms->n.next = ms->n.prev = NULL;
+  if (!signal_is_active(ms))
+    return;
+  clist_unlink(&ms->n);
 
   int another = 0;
   CLIST_FOR_EACH(struct main_signal *, s, m->signal_list)
@@ -457,247 +579,312 @@ signal_del(struct main_signal *ms)
       another++;
   if (!another)
     {
-      sigset_t ss;
-      sigemptyset(&ss);
-      sigaddset(&ss, ms->signum);
-      THREAD_SIGMASK(SIG_BLOCK, &ss, NULL);
+      if (main_is_current(m))
+	{
+	  sigset_t ss;
+	  sigemptyset(&ss);
+	  sigaddset(&ss, ms->signum);
+	  THREAD_SIGMASK(SIG_BLOCK, &ss, NULL);
+	}
       sigdelset(&m->want_signals, ms->signum);
     }
 }
 
+void
+signal_del(struct main_signal *ms)
+{
+  signal_del_ctx(main_current(), ms);
+}
+
+#ifdef CONFIG_UCW_DEBUG
+
+void
+file_debug(struct main_file *fi)
+{
+  msg(L_DEBUG, "\t\t%p (fd %d, rh %p, wh %p, data %p)",
+    fi, fi->fd, fi->read_handler, fi->write_handler, fi->data);
+}
+
+void
+hook_debug(struct main_hook *ho)
+{
+  msg(L_DEBUG, "\t\t%p (func %p, data %p)", ho, ho->handler, ho->data);
+}
+
+void
+signal_debug(struct main_signal *sg)
+{
+  if (sg->signum < 0)
+    msg(L_DEBUG, "\t\t(placeholder)");
+  else
+    msg(L_DEBUG, "\t\t%p (sig %d, func %p, data %p)", sg, sg->signum, sg->handler, sg->data);
+}
+
+static void
+timer_debug_ctx(struct main_context *m, struct main_timer *tm)
+{
+  msg(L_DEBUG, "\t\t%p (expires %lld, data %p)", tm, (long long)(tm->expires - m->now), tm->data);
+}
+
+void
+timer_debug(struct main_timer *tm)
+{
+  timer_debug_ctx(main_current(), tm);
+}
+
+void
+process_debug(struct main_process *pr)
+{
+  msg(L_DEBUG, "\t\t%p (pid %d, func %p, data %p)", pr, pr->pid, pr->handler, pr->data);
+}
+
 void
 main_debug_context(struct main_context *m UNUSED)
 {
-#ifdef CONFIG_DEBUG
   msg(L_DEBUG, "### Main loop status on %lld", (long long) m->now);
   msg(L_DEBUG, "\tActive timers:");
   uns num_timers = count_timers(m);
   for (uns i = 1; i <= num_timers; i++)
-    {
-      struct main_timer *tm = m->timer_table[i];
-      msg(L_DEBUG, "\t\t%p (expires %lld, data %p)", tm, (long long)(tm->expires ? tm->expires - m->now : 999999), tm->data);
-    }
+    timer_debug(m->timer_table[i]);
   msg(L_DEBUG, "\tActive files:");
   CLIST_FOR_EACH(struct main_file *, fi, m->file_list)
-    msg(L_DEBUG, "\t\t%p (fd %d, rh %p, wh %p, data %p)",
-	fi, fi->fd, fi->read_handler, fi->write_handler, fi->data);
-    // FIXME: Can we display status of block_io requests somehow?
+    file_debug(fi);
+  CLIST_FOR_EACH(struct main_file *, fi, m->file_active_list)
+    file_debug(fi);
+#ifdef CONFIG_UCW_EPOLL
+  CLIST_FOR_EACH(struct main_file *, fi, m->file_recalc_list)
+    file_debug(fi);
+#endif
   msg(L_DEBUG, "\tActive hooks:");
   CLIST_FOR_EACH(struct main_hook *, ho, m->hook_done_list)
-    msg(L_DEBUG, "\t\t%p (func %p, data %p)", ho, ho->handler, ho->data);
+    hook_debug(ho);
   CLIST_FOR_EACH(struct main_hook *, ho, m->hook_list)
-    msg(L_DEBUG, "\t\t%p (func %p, data %p)", ho, ho->handler, ho->data);
+    hook_debug(ho);
   msg(L_DEBUG, "\tActive processes:");
   CLIST_FOR_EACH(struct main_process *, pr, m->process_list)
-    msg(L_DEBUG, "\t\t%p (pid %d, func %p, data %p)", pr, pr->pid, pr->handler, pr->data);
+    process_debug(pr);
   msg(L_DEBUG, "\tActive signal catchers:");
   CLIST_FOR_EACH(struct main_signal *, sg, m->signal_list)
-    msg(L_DEBUG, "\t\t%p (sig %d, func %p, data %p)", sg, sg->signum, sg->handler, sg->data);
+    signal_debug(sg);
+}
+
+#else
+
+// Stubs
+void file_debug(struct main_file *fi UNUSED) { }
+void hook_debug(struct main_hook *ho UNUSED) { }
+void signal_debug(struct main_signal *sg UNUSED) { }
+void timer_debug(struct main_timer *tm UNUSED) { }
+void process_debug(struct main_process *pr UNUSED) { }
+void main_debug_context(struct main_context *m UNUSED) { }
+
 #endif
+
+static void
+process_timers(struct main_context *m)
+{
+  struct main_timer *tm;
+  while (count_timers(m) && (tm = m->timer_table[1])->expires <= m->now)
+    {
+      DBG("MAIN: Timer %p expired at now-%lld", tm, (long long)(m->now - tm->expires));
+      tm->handler(tm);
+    }
 }
 
+static enum main_hook_return
+process_hooks(struct main_context *m)
+{
+  int hook_min = HOOK_RETRY;
+  int hook_max = HOOK_SHUTDOWN;
+  struct main_hook *ho;
+
+  while (ho = clist_remove_head(&m->hook_list))
+    {
+      clist_add_tail(&m->hook_done_list, &ho->n);
+      DBG("MAIN: Hook %p", ho);
+      int ret = ho->handler(ho);
+      hook_min = MIN(hook_min, ret);
+      hook_max = MAX(hook_max, ret);
+    }
+  clist_move(&m->hook_list, &m->hook_done_list);
+  if (hook_min == HOOK_SHUTDOWN ||
+    hook_min == HOOK_DONE && hook_max == HOOK_DONE ||
+    m->shutdown)
+    {
+      DBG("MAIN: Shut down by %s", m->shutdown ? "main_shut_down" : "a hook");
+      return HOOK_SHUTDOWN;
+    }
+  if (hook_max == HOOK_RETRY)
+    return HOOK_RETRY;
+  else
+    return HOOK_IDLE;
+}
+
+#ifdef CONFIG_UCW_EPOLL
+
 static void
-main_rebuild_poll_table(struct main_context *m)
+recalc_files(struct main_context *m)
 {
   struct main_file *fi;
-  if (m->poll_table_size < m->file_cnt)
+
+  while (fi = clist_remove_head(&m->file_recalc_list))
     {
-      if (m->poll_table)
-	xfree(m->poll_table);
-      else
-	m->poll_table_size = 1;
-      while (m->poll_table_size < m->file_cnt)
-	m->poll_table_size *= 2;
-      m->poll_table = xmalloc(sizeof(struct pollfd) * m->poll_table_size);
+      struct epoll_event evt = {
+	.events = file_want_events(fi),
+	.data.ptr = fi,
+      };
+      if (evt.events != fi->last_want_events)
+	{
+	  DBG("MAIN: Changing requested events for fd %d to %x", fi->fd, evt.events);
+	  fi->last_want_events = evt.events;
+	  if (epoll_ctl(main_current()->epoll_fd, EPOLL_CTL_MOD, fi->fd, &evt) < 0)
+	    die("epoll_ctl() failed: %m");
+	}
+      clist_add_tail(&m->file_list, &fi->n);
     }
+}
+
+#else
+
+static void
+rebuild_poll_table(struct main_context *m)
+{
+  GARY_INIT_OR_RESIZE(m->poll_table, m->file_cnt);
+  GARY_INIT_OR_RESIZE(m->poll_file_table, m->file_cnt);
+  DBG("MAIN: Rebuilding poll table: %d entries", m->file_cnt);
+
   struct pollfd *p = m->poll_table;
-  DBG("MAIN: Rebuilding poll table: %d of %d entries set", m->file_cnt, m->poll_table_size);
-  CLIST_WALK(fi, m->file_list)
+  struct main_file **pf = m->poll_file_table;
+  CLIST_FOR_EACH(struct main_file *, fi, m->file_list)
     {
       p->fd = fi->fd;
+      p->events = file_want_events(fi);
       fi->pollfd = p++;
-      file_chg(fi);
+      *pf++ = fi;
     }
   m->poll_table_obsolete = 0;
 }
 
+#endif
+
 void
 main_loop(void)
 {
   DBG("MAIN: Entering main_loop");
   struct main_context *m = main_current();
 
-  struct main_file *fi;
-  struct main_hook *ho;
-  struct main_timer *tm;
+  main_get_time_ctx(m);
+  m->shutdown = 0;
 
-  do_main_get_time(m);
   for (;;)
     {
       timestamp_t wake = m->now + 1000000000;
-      while (GARY_SIZE(m->timer_table) > 1 && (tm = m->timer_table[1])->expires <= m->now)
+      process_timers(m);
+      switch (process_hooks(m))
 	{
-	  DBG("MAIN: Timer %p expired at now-%lld", tm, (long long)(m->now - tm->expires));
-	  tm->handler(tm);
+	case HOOK_SHUTDOWN:
+	  return;
+	case HOOK_RETRY:
+	  wake = 0;
+	  break;
+	default: ;
 	}
-      int hook_min = HOOK_RETRY;
-      int hook_max = HOOK_SHUTDOWN;
-      while (ho = clist_remove_head(&m->hook_list))
+
+      int timeout = 0;
+      if (!m->single_step)
 	{
-	  clist_add_tail(&m->hook_done_list, &ho->n);
-	  DBG("MAIN: Hook %p", ho);
-	  int ret = ho->handler(ho);
-	  hook_min = MIN(hook_min, ret);
-	  hook_max = MAX(hook_max, ret);
+	  if (count_timers(m))
+	    wake = MIN(wake, m->timer_table[1]->expires);
+	  main_get_time_ctx(m);
+	  timeout = ((wake > m->now) ? wake - m->now : 0);
 	}
-      clist_move(&m->hook_list, &m->hook_done_list);
-      if (hook_min == HOOK_SHUTDOWN ||
-	  hook_min == HOOK_DONE && hook_max == HOOK_DONE ||
-	  m->shutdown)
-	{
-	  DBG("MAIN: Shut down by %s", m->shutdown ? "main_shutdown" : "a hook");
-	  return;
-	}
-      if (hook_max == HOOK_RETRY)
-	wake = 0;
+
+#ifdef CONFIG_UCW_EPOLL
+      recalc_files(m);
+      DBG("MAIN: Epoll for %d fds and timeout %d ms", m->file_cnt, timeout);
+      int n = epoll_wait(m->epoll_fd, m->epoll_events, EPOLL_BUF_SIZE, timeout);
+#else
       if (m->poll_table_obsolete)
-	main_rebuild_poll_table(m);
-      if (count_timers(m) && (tm = m->timer_table[1])->expires < wake)
-	wake = tm->expires;
-      do_main_get_time(m);
-      int timeout = ((wake > m->now) ? wake - m->now : 0);
+	rebuild_poll_table(m);
       DBG("MAIN: Poll for %d fds and timeout %d ms", m->file_cnt, timeout);
-      int p = poll(m->poll_table, m->file_cnt, timeout);
+      int n = poll(m->poll_table, m->file_cnt, timeout);
+#endif
+
+      DBG("\t-> %d events", n);
+      if (n < 0 && errno != EAGAIN && errno != EINTR)
+	die("(e)poll failed: %m");
       timestamp_t old_now = m->now;
-      do_main_get_time(m);
+      main_get_time_ctx(m);
       m->idle_time += m->now - old_now;
-      if (p > 0)
+
+      if (n <= 0)
 	{
-	  struct pollfd *p = m->poll_table;
-	  CLIST_WALK(fi, m->file_list)
-	    {
-	      if (p->revents & (POLLIN | POLLHUP | POLLERR))
-		{
-		  do
-		    DBG("MAIN: Read event on fd %d", p->fd);
-		  while (fi->read_handler && fi->read_handler(fi) && !m->poll_table_obsolete);
-		  if (m->poll_table_obsolete)	/* File entries have been inserted or deleted => better not risk continuing to nowhere */
-		    break;
-		}
-	      if (p->revents & (POLLOUT | POLLERR))
-		{
-		  do
-		    DBG("MAIN: Write event on fd %d", p->fd);
-		  while (fi->write_handler && fi->write_handler(fi) && !m->poll_table_obsolete);
-		  if (m->poll_table_obsolete)
-		    break;
-		}
-	      p++;
-	    }
+	  if (m->single_step)
+	    return;
+	  else
+	    continue;
 	}
-    }
-}
-
-#ifdef TEST
-
-static struct main_process mp;
-static struct main_block_io fin, fout;
-static struct main_hook hook;
-static struct main_timer tm;
-static struct main_signal sg;
 
-static byte rb[16];
+      // Relink all files with a pending event to file_active_list
+#ifdef CONFIG_UCW_EPOLL
+      for (int i=0; i<n; i++)
+	{
+	  struct epoll_event *e = &m->epoll_events[i];
+	  struct main_file *fi = e->data.ptr;
+	  clist_remove(&fi->n);
+	  clist_add_tail(&m->file_active_list, &fi->n);
+	  fi->events = e->events;
+	}
+#else
+      struct pollfd *p = m->poll_table;
+      struct main_file **pf = m->poll_file_table;
+      for (uns i=0; i < m->file_cnt; i++)
+	if (p[i].revents)
+	  {
+	    struct main_file *fi = pf[i];
+	    clist_remove(&fi->n);
+	    clist_add_tail(&m->file_active_list, &fi->n);
+	    fi->events = p[i].revents;
+	  }
+#endif
 
-static void dread(struct main_block_io *bio)
-{
-  if (bio->rpos < bio->rlen)
-    {
-      msg(L_INFO, "Read EOF");
-      block_io_del(bio);
-    }
-  else
-    {
-      msg(L_INFO, "Read done");
-      block_io_read(bio, rb, sizeof(rb));
+      /*
+       *  Process the buffered file events. This is pretty tricky, since
+       *  user callbacks can modify the file structure or even destroy it.
+       *  In such cases, we detect that the structure was relinked and stop
+       *  processing its events, leaving them for the next iteration of the
+       *  main loop.
+       */
+      struct main_file *fi;
+      while (fi = clist_head(&m->file_active_list))
+	{
+	  if (fi->read_handler && (fi->events & (POLLIN | POLLHUP)))
+	    {
+	      fi->events &= ~(POLLIN | POLLHUP);
+	      do
+		DBG("MAIN: Read event on fd %d", fi->fd);
+	      while (fi->read_handler && fi->read_handler(fi));
+	      continue;
+	    }
+	  if (fi->write_handler && (fi->events & (POLLOUT | POLLHUP | POLLERR)))
+	    {
+	      fi->events &= ~(POLLOUT | POLLHUP | POLLERR);
+	      do
+		DBG("MAIN: Write event on fd %d", fi->fd);
+	      while (fi->write_handler && fi->write_handler(fi));
+	      continue;
+	    }
+	  clist_remove(&fi->n);
+	  clist_add_tail(&m->file_list, &fi->n);
+	}
     }
 }
 
-static void derror(struct main_block_io *bio, int cause)
-{
-  msg(L_INFO, "Error: %m !!! (cause %d)", cause);
-  block_io_del(bio);
-}
-
-static void dwrite(struct main_block_io *bio UNUSED)
-{
-  msg(L_INFO, "Write done");
-}
-
-static int dhook(struct main_hook *ho UNUSED)
-{
-  msg(L_INFO, "Hook called");
-  return 0;
-}
-
-static void dtimer(struct main_timer *tm)
-{
-  msg(L_INFO, "Timer tick");
-  timer_add_rel(tm, 11000);
-  timer_add_rel(tm, 10000);
-}
-
-static void dentry(void)
-{
-  msg(L_INFO, "*** SUBPROCESS START ***");
-  sleep(2);
-  msg(L_INFO, "*** SUBPROCESS FINISH ***");
-  exit(0);
-}
-
-static void dexit(struct main_process *pr)
-{
-  msg(L_INFO, "Subprocess %d exited with status %x", pr->pid, pr->status);
-}
-
-static void dsignal(struct main_signal *sg UNUSED)
-{
-  msg(L_INFO, "SIGINT received (use Ctrl-\\ to really quit)");
-}
-
-int
-main(void)
+void
+main_step(void)
 {
-  log_init(NULL);
-  main_init();
-
-  fin.read_done = dread;
-  fin.error_handler = derror;
-  block_io_add(&fin, 0);
-  block_io_read(&fin, rb, sizeof(rb));
-
-  fout.write_done = dwrite;
-  fout.error_handler = derror;
-  block_io_add(&fout, 1);
-  block_io_write(&fout, "Hello, world!\n", 14);
-
-  hook.handler = dhook;
-  hook_add(&hook);
-
-  tm.handler = dtimer;
-  timer_add_rel(&tm,  1000);
-
-  sg.signum = SIGINT;
-  sg.handler = dsignal;
-  signal_add(&sg);
-
-  mp.handler = dexit;
-  if (!process_fork(&mp))
-    dentry();
-
-  main_debug();
-
+  struct main_context *m = main_current();
+  m->single_step = 1;
   main_loop();
-  msg(L_INFO, "Finished.");
+  m->single_step = 0;
 }
-
-#endif