multi: add curl_multi_wakeup()

This commit adds curl_multi_wakeup() which was previously in the TODO
list under the curl_multi_unblock name.

On some platforms and with some configurations this feature might not be
available or can fail, in these cases a new error code
(CURLM_WAKEUP_FAILURE) is returned from curl_multi_wakeup().

Fixes #4418
Closes #4608

tests/data/Makefile.inc

@@ -179,7 +179,7 @@ test1525 test1526 test1527 test1528 test1529 test1530 test1531 test1532 \
 test1533 test1534 test1535 test1536 test1537 test1538 \
 test1540 test1541 \
 test1550 test1551 test1552 test1553 test1554 test1555 test1556 test1557 \
-test1558 test1559 test1560 test1561 test1562 test1563 \
+test1558 test1559 test1560 test1561 test1562 test1563 test1564 test1565 \
 \
 test1590 test1591 test1592 test1593 test1594 test1595 test1596 \
 \

tests/data/test1135

@@ -92,6 +92,7 @@ CURL_EXTERN CURLMcode curl_multi_remove_handle(CURLM *multi_handle,
 CURL_EXTERN CURLMcode curl_multi_fdset(CURLM *multi_handle,
 CURL_EXTERN CURLMcode curl_multi_wait(CURLM *multi_handle,
 CURL_EXTERN CURLMcode curl_multi_poll(CURLM *multi_handle,
+CURL_EXTERN CURLMcode curl_multi_wakeup(CURLM *multi_handle);
 CURL_EXTERN CURLMcode curl_multi_perform(CURLM *multi_handle,
 CURL_EXTERN CURLMcode curl_multi_cleanup(CURLM *multi_handle);
 CURL_EXTERN CURLMsg *curl_multi_info_read(CURLM *multi_handle,

tests/data/test1538

@@ -139,7 +139,8 @@ m5: Invalid socket argument
 m6: Unknown option
 m7: The easy handle is already added to a multi handle
 m8: API function called from within callback
-m9: Unknown error
+m9: Wakeup is unavailable or failed
+m10: Unknown error
 s0: No error
 s1: Unknown share option
 s2: Share currently in use

tests/data/test1564

@@ -0,0 +1,31 @@
+<testcase>
+<info>
+<keywords>
+multi
+wakeup
+</keywords>
+</info>
+
+# Server-side
+<reply>
+</reply>
+
+# Client-side
+<client>
+<server>
+none
+</server>
+<tool>
+lib1564
+</tool>
+<name>
+wakeup before poll with no easy handles
+</name>
+<command>
+</command>
+</client>
+
+# Verify data after the test has been "shot"
+<verify>
+</verify>
+</testcase>

tests/data/test1565

@@ -0,0 +1,41 @@
+<testcase>
+<info>
+<keywords>
+HTTP
+HTTP GET
+multi
+multi-threaded
+wakeup
+</keywords>
+</info>
+
+# Server-side
+<reply>
+<data nocheck="yes">
+HTTP/1.1 200 OK
+Content-Length: 3
+
+OK
+</data>
+</reply>
+
+# Client-side
+<client>
+<server>
+http
+</server>
+<tool>
+lib1565
+</tool>
+<name>
+wakeup from another thread
+</name>
+<command>
+http://%HOSTIP:%HTTPPORT/1
+</command>
+</client>
+
+# Verify data after the test has been "shot"
+<verify>
+</verify>
+</testcase>