Retry poll(2) if we are intterupted.

This commit adds logic to retry our poll call when waiting for the
connection to complete, in the event that we are interrupted by a
signal.

Additionally we do some simple bookkeeping to keep track of the overall
timeout specified by the user.

Fixes #1206

net.c

@@ -41,6 +41,7 @@
 #include <stdio.h>
 #include <limits.h>
 #include <stdlib.h>
+#include <time.h>
 
 #include "net.h"
 #include "sds.h"
@@ -271,37 +272,54 @@ static int redisContextTimeoutMsec(redisContext *c, long *result)
     return REDIS_OK;
 }
 
+static long redisPollMillis(void) {
+#ifndef _MSC_VER
+    struct timespec now;
+    clock_gettime(CLOCK_MONOTONIC, &now);
+    return (now.tv_sec * 1000) + now.tv_nsec / 1000000;
+#else
+    FILETIME ft;
+    GetSystemTimeAsFileTime(&ft);
+    return (((long long)ft.dwHighDateTime << 32) | ft.dwLowDateTime) / 10;
+#endif
+}
+
 static int redisContextWaitReady(redisContext *c, long msec) {
-    struct pollfd   wfd[1];
-
-    wfd[0].fd     = c->fd;
-    wfd[0].events = POLLOUT;
-
-    if (errno == EINPROGRESS) {
+    struct pollfd wfd;
+    long end;
     int res;
 
-        if ((res = poll(wfd, 1, msec)) == -1) {
-            __redisSetErrorFromErrno(c, REDIS_ERR_IO, "poll(2)");
-            redisNetClose(c);
-            return REDIS_ERR;
-        } else if (res == 0) {
-            errno = ETIMEDOUT;
+    if (errno != EINPROGRESS) {
         __redisSetErrorFromErrno(c,REDIS_ERR_IO,NULL);
         redisNetClose(c);
         return REDIS_ERR;
     }
 
+    wfd.fd = c->fd;
+    wfd.events = POLLOUT;
+    end = msec >= 0 ? redisPollMillis() + msec : 0;
+
+    while ((res = poll(&wfd, 1, msec)) <= 0) {
+        if (res < 0 && errno != EINTR) {
+            __redisSetErrorFromErrno(c, REDIS_ERR_IO, "poll(2)");
+            redisNetClose(c);
+            return REDIS_ERR;
+        } else if (res == 0 || (msec >= 0 && redisPollMillis() >= end)) {
+            errno = ETIMEDOUT;
+            __redisSetErrorFromErrno(c, REDIS_ERR_IO, NULL);
+            redisNetClose(c);
+            return REDIS_ERR;
+        } else {
+            /* res < 0 && errno == EINTR, try again */
+        }
+    }
+
     if (redisCheckConnectDone(c, &res) != REDIS_OK || res == 0) {
         redisCheckSocketError(c);
         return REDIS_ERR;
     }
 
     return REDIS_OK;
-    }
-
-    __redisSetErrorFromErrno(c,REDIS_ERR_IO,NULL);
-    redisNetClose(c);
-    return REDIS_ERR;
 }
 
 int redisCheckConnectDone(redisContext *c, int *completed) {