curl_multi_wait: reduce timeout if the multi handle wants to

If the multi handle's pending timeout is less than what is passed into
this function, it will now opt to use the shorter time anyway since it
is a very good hint that the handle wants to process something in a
shorter time than what otherwise would happen.

curl_multi_wait.3 was updated accordingly to clarify

This is the reason for bug #1224

Bug: http://curl.haxx.se/bug/view.cgi?id=1224
Reported-by: Andrii Moiseiev

diff --git a/docs/libcurl/curl_multi_wait.3 b/docs/libcurl/curl_multi_wait.3
index b14760b..c266f25 100644 (file)
--- a/docs/libcurl/curl_multi_wait.3
+++ b/docs/libcurl/curl_multi_wait.3
@@ -5,7 +5,7 @@
 .\" *                            | (__| |_| |  _ <| |___
 .\" *                             \___|\___/|_| \_\_____|
 .\" *
-.\" * Copyright (C) 1998 - 2012, Daniel Stenberg, <daniel@haxx.se>, et al.
+.\" * Copyright (C) 1998 - 2013, Daniel Stenberg, <daniel@haxx.se>, et al.
 .\" *
 .\" * This software is licensed as described in the file COPYING, which
 .\" * you should have received as part of this distribution. The terms
@@ -36,6 +36,9 @@ CURLMcode curl_multi_wait(CURLM *multi_handle,
 This function polls on all file descriptors used by the curl easy handles
 contained in the given multi handle set.  It will block until activity is
 detected on at least one of the handles or \fItimeout_ms\fP has passed.
+Alternatively, if the multi handle has a pending internal timeout that has a
+shorter expiry time than \fItimeout_ms\fP, that shorter time will be used
+instead to make sure timeout accuracy is reasonably kept.
 
 The calling application may pass additional curl_waitfd structures which are
 similar to \fIpoll(2)\fP's pollfd structure to be waited on in the same call.

diff --git a/lib/multi.c b/lib/multi.c
index ef40383..e4b3369 100644 (file)
--- a/lib/multi.c
+++ b/lib/multi.c
@@ -76,6 +76,8 @@ static bool isHandleAtHead(struct SessionHandle *handle,
 static CURLMcode add_next_timeout(struct timeval now,
                                   struct Curl_multi *multi,
                                   struct SessionHandle *d);
+static CURLMcode multi_timeout(struct Curl_multi *multi,
+                               long *timeout_ms);
 
 #ifdef DEBUGBUILD
 static const char * const statename[]={
@@ -810,10 +812,17 @@ CURLMcode curl_multi_wait(CURLM *multi_handle,
   unsigned int nfds = 0;
   unsigned int curlfds;
   struct pollfd *ufds = NULL;
+  long timeout_internal;
 
   if(!GOOD_MULTI_HANDLE(multi))
     return CURLM_BAD_HANDLE;
 
+  /* If the internally desired timeout is actually shorter than requested from
+     the outside, then use the shorter time! */
+  (void)multi_timeout(multi, &timeout_internal);
+  if(timeout_internal < (long)timeout_ms)
+    timeout_ms = (int)timeout_internal;
+
   /* Count up how many fds we have from the multi handle */
   easy=multi->easy.next;
   while(easy != &multi->easy) {