[Xen-changelog] [xen staging] libxl: event: Move poller pipe emptying to the end of afterpoll

[patchbot@xxxxxxx]

commit 0b70b2ff8f5a61196d090cc70040a20178327347
Author:     Ian Jackson <ian.jackson@xxxxxxxxxxxxx>
AuthorDate: Fri Jan 10 13:19:36 2020 +0000
Commit:     Ian Jackson <ian.jackson@xxxxxxxxxxxxx>
CommitDate: Mon Jan 27 16:03:18 2020 +0000

    libxl: event: Move poller pipe emptying to the end of afterpoll
    
    This seems neater.  It doesn't have any significant effect because:
    
    The poller fd wouldn't be emptied by time_occurs.  It would only be
    woken by time_occurs as a result of an ao completing, or by
    libxl__egc_ao_cleanup_1_baton.  But ...1_baton won't be called in
    between (for one thing, this would violate the rule of not still
    having the active caller when ...1_baton is called).
    
    While discussing this patch, I noticed that there is a possibility (in
    libxl in general) that poller_put might be called on a woken poller.
    It would probably be sensible at some point to make poller_get empty
    the pipe, at least if the pipe_nonempty flag is set.
    
    Signed-off-by: Ian Jackson <ian.jackson@xxxxxxxxxxxxx>
    Tested-by: George Dunlap <george.dunlap@xxxxxxxxxx>
    Reviewed-by: George Dunlap <george.dunlap@xxxxxxxxxx>
    ---
    v3: Completely revised commit message; now we think this is just
        cleanup.
---
 tools/libxl/libxl_event.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/tools/libxl/libxl_event.c b/tools/libxl/libxl_event.c
index 5f6a607d80..7c5387e94f 100644
--- a/tools/libxl/libxl_event.c
+++ b/tools/libxl/libxl_event.c
@@ -1453,12 +1453,6 @@ static void afterpoll_internal(libxl__egc *egc, 
libxl__poller *poller,
         fd_occurs(egc, efd, revents);
     }
 
-    if (afterpoll_check_fd(poller,fds,nfds, poller->wakeup_pipe[0],POLLIN)) {
-        poller->pipe_nonempty = 0;
-        int e = libxl__self_pipe_eatall(poller->wakeup_pipe[0]);
-        if (e) LIBXL__EVENT_DISASTER(gc, "read wakeup", e, 0);
-    }
-
     for (;;) {
         libxl__ev_time *etime = LIBXL_TAILQ_FIRST(&CTX->etimes);
         if (!etime)
@@ -1473,6 +1467,12 @@ static void afterpoll_internal(libxl__egc *egc, 
libxl__poller *poller,
 
         time_occurs(egc, etime, ERROR_TIMEDOUT);
     }
+
+    if (afterpoll_check_fd(poller,fds,nfds, poller->wakeup_pipe[0],POLLIN)) {
+        poller->pipe_nonempty = 0;
+        int e = libxl__self_pipe_eatall(poller->wakeup_pipe[0]);
+        if (e) LIBXL__EVENT_DISASTER(gc, "read wakeup", e, 0);
+    }
 }
 
 void libxl_osevent_afterpoll(libxl_ctx *ctx, int nfds, const struct pollfd 
*fds,
--
generated by git-patchbot for /home/xen/git/xen.git#staging

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