[Xen-changelog] [xen master] libxl: event handling: ao_inprogress does waits while reports outstanding

[patchbot@xxxxxxx]

commit f1335f0d7b2402e94e0c6e8a905dc309edaafcfb
Author:     Ian Jackson <ian.jackson@xxxxxxxxxxxxx>
AuthorDate: Mon Feb 9 15:20:32 2015 +0000
Commit:     Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>
CommitDate: Mon Feb 9 17:41:32 2015 +0000

    libxl: event handling: ao_inprogress does waits while reports outstanding
    
    libxl__ao_inprogress needs to check (like
    libxl__ao_complete_check_progress_reports) that there are no
    oustanding progress callbacks.
    
    Otherwise it might happen that we would destroy the ao while another
    thread has an outstanding callback its egc report queue.  The other
    thread would then, in its egc_run_callbacks, touch the destroyed ao.
    
    Instead, when this happens in libxl__ao_inprogress, simply run round
    the event loop again.  The thread which eventually makes the callback
    will spot our poller in the ao, and notify the poller, waking us up.
    
    This fixes an assertion failure race seen with libvirt:
      libvirtd: libxl_event.c:1792: libxl__ao_complete_check_progress_reports: 
Assertion `ao->in_initiator' failed.
    or (after "Add an assert to egc_run_callbacks")
      libvirtd: libxl_event.c:1338: egc_run_callbacks: Assertion 
`aop->ao->magic == 0xA0FACE00ul' failed.
    
    Signed-off-by: Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>
    CC: Ian Campbell <ian.campbell@xxxxxxxxxx>
    CC: Wei Liu <wei.liu2@xxxxxxxxxx>
    CC: Jim Fehlig <jfehlig@xxxxxxxx>
    Acked-by: Wei Liu <wei.liu2@xxxxxxxxxx>
---
 tools/libxl/libxl_event.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/tools/libxl/libxl_event.c b/tools/libxl/libxl_event.c
index 89ca6d2..595da2b 100644
--- a/tools/libxl/libxl_event.c
+++ b/tools/libxl/libxl_event.c
@@ -1878,7 +1878,7 @@ int libxl__ao_inprogress(libxl__ao *ao,
         for (;;) {
             assert(ao->magic == LIBXL__AO_MAGIC);
 
-            if (ao->complete) {
+            if (!ao_work_outstanding(ao)) {
                 rc = ao->rc;
                 ao->notified = 1;
                 break;
--
generated by git-patchbot for /home/xen/git/xen.git#master

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