*: remove THREAD_ON macros, add nullity check

The way thread.c is written, a caller who wishes to be able to cancel a
thread or avoid scheduling it twice must keep a reference to the thread.
Typically this is done with a long lived pointer whose value is checked
for null in order to know if the thread is currently scheduled.  The
check-and-schedule idiom is so common that several wrapper macros in
thread.h existed solely to provide it.

This patch removes those macros and adds a new parameter to all
thread_add_* functions which is a pointer to the struct thread * to
store the result of a scheduling call. If the value passed is non-null,
the thread will only be scheduled if the value is null. This helps with
consistency.

A Coccinelle spatch has been used to transform code of the form:

  if (t == NULL)
    t = thread_add_* (...)

to the form

  thread_add_* (..., &t)

The THREAD_ON macros have also been transformed to the underlying
thread.c calls.

Signed-off-by: Quentin Young <qlyoung@cumulusnetworks.com>

1 files changed, 3 insertions, 2 deletions

diff --git a/lib/agentx.c b/lib/agentx.c
index 11d5c9385d..f7b124f25b 100644
--- a/lib/agentx.c
+++ b/lib/agentx.c
@@ -86,7 +86,8 @@ agentx_events_update(void)
   snmp_select_info (&maxfd, &fds, &timeout, &block);
 
   if (!block)
-    timeout_thr = thread_add_timer_tv (agentx_tm, agentx_timeout, NULL, &timeout);
+    timeout_thr = thread_add_timer_tv(agentx_tm, agentx_timeout, NULL,
+                                      &timeout, NULL);
 
   ln = listhead (events);
   thr = ln ? listgetdata (ln) : NULL;
@@ -114,7 +115,7 @@ agentx_events_update(void)
       else if (FD_ISSET (fd, &fds))
         {
           struct listnode *newln;
-          thr = thread_add_read (agentx_tm, agentx_read, NULL, fd);
+          thr = thread_add_read(agentx_tm, agentx_read, NULL, fd, NULL);
           newln = listnode_add_before (events, ln, thr);
           thr->arg = newln;
         }