poll: Document reentrancy restriction on before()

[secnet.git] / secnet.h

diff --git a/secnet.h b/secnet.h
index 40ad1d3e31fd4d50c5a5ce208043ff88c5a4d18b..72e3e7cdf79c982b50333351ef588a41a8252777 100644 (file)
--- a/secnet.h
+++ b/secnet.h
@@ -198,7 +198,14 @@ int32_t calculate_max_start_pad(void);
 
 /* If nfds_io is insufficient for your needs, set it to the required
    number and return ERANGE. timeout is in milliseconds; if it is too
-   high then lower it. It starts at -1 (==infinite) */
+   high then lower it. It starts at -1 (==infinite). */
+/* Note that beforepoll_fn may NOT do anything which might change the
+   fds or timeouts wanted by other registered poll loop loopers.
+   Callers should make sure of this by not making any calls into other
+   modules from the beforepoll_fn; the easiest way to ensure this is
+   for beforepoll_fn to only retreive information and not take any
+   action.
+ */
 typedef int beforepoll_fn(void *st, struct pollfd *fds, int *nfds_io,
                          int *timeout_io);
 typedef void afterpoll_fn(void *st, struct pollfd *fds, int nfds);