From: Ian Jackson Date: Mon, 9 Feb 2015 15:20:32 +0000 (+0000) Subject: libxl: event handling: ao_inprogress does waits while reports outstanding X-Git-Url: http://xenbits.xensource.com/gitweb?a=commitdiff_plain;h=a5a730a4e6445d2762c1640189eddd306d8a0ae3;p=xen.git 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 CC: Ian Campbell CC: Wei Liu CC: Jim Fehlig Acked-by: Wei Liu (cherry picked from commit f1335f0d7b2402e94e0c6e8a905dc309edaafcfb) (cherry picked from commit dfed6d96fd6af00c9970e2a1c600d6bb991d137e) (cherry picked from commit 32f82fa8d9f6ea0eddfd6ab38c0b867b54f99f14) --- diff --git a/tools/libxl/libxl_event.c b/tools/libxl/libxl_event.c index 63ba4d2bd3..81bb4885a2 100644 --- a/tools/libxl/libxl_event.c +++ b/tools/libxl/libxl_event.c @@ -1679,7 +1679,7 @@ 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;