[commit: ghc] ghc-7.4: Disable the timer signal while blocked in select() (#5991) (6aee474)

[Paolo Capriotti]

Repository : ssh://darcs.haskell.org//srv/darcs/ghc

On branch  : ghc-7.4

http://hackage.haskell.org/trac/ghc/changeset/6aee474574e0aff10602a6fd17d37826b04a996d

>---------------------------------------------------------------

commit 6aee474574e0aff10602a6fd17d37826b04a996d
Author: Simon Marlow <marlowsd at gmail.com>
Date:   Wed Apr 11 10:12:14 2012 +0100

    Disable the timer signal while blocked in select() (#5991)
    
    The threaded RTS had a fix for this a long time ago (#1623) but this
    patch applies a similar fix to the non-threaded RTS.
    
    MERGED from commit dd24d6bc37879c6b32a3d5ac4ee765e59e13501c

>---------------------------------------------------------------

 rts/posix/Select.c |   15 ++++++++++++---
 1 files changed, 12 insertions(+), 3 deletions(-)

diff --git a/rts/posix/Select.c b/rts/posix/Select.c
index a3f2ae3..0b3f750 100644
--- a/rts/posix/Select.c
+++ b/rts/posix/Select.c
@@ -217,10 +217,19 @@ awaitEvent(rtsBool wait)
           ptv = NULL;
       }
 
-      /* Check for any interesting events */
+      while (1) { // repeat the select on EINTR
       
-      while ((numFound = select(maxfd+1, &rfd, &wfd, NULL, ptv)) < 0) {
-	  if (errno != EINTR) {
+          // Disable the timer signal while blocked in
+          // select(), to conserve power. (#1623, #5991)
+          if (wait) stopTimer();
+
+          numFound = select(maxfd+1, &rfd, &wfd, NULL, ptv);
+
+          if (wait) startTimer();
+
+          if (numFound >= 0) break;
+
+          if (errno != EINTR) {
 	    /* Handle bad file descriptors by unblocking all the
 	       waiting threads. Why? Because a thread might have been
 	       a bit naughty and closed a file descriptor while another