Am 21.11.2017 um 03:23 hat Jeff Cody geschrieben: > The previous patch fixed a race condition, in which there were > coroutines being executing doubly, or after coroutine deletion. > > We can detect common scenarios when this happens, and print an error > message and abort before we corrupt memory / data, or segfault. > > This patch will abort if an attempt to enter a coroutine is made while > it is currently pending execution, either in a specific AioContext bh, > or pending execution via a timer. It will also abort if a coroutine > is scheduled, before a prior scheduled run has occured. > > We cannot rely on the existing co->caller check for recursive re-entry > to catch this, as the coroutine may run and exit with > COROUTINE_TERMINATE before the scheduled coroutine executes. > > (This is the scenario that was occuring and fixed in the previous > patch). > > Signed-off-by: Jeff Cody <jc...@redhat.com> > --- > include/qemu/coroutine_int.h | 6 ++++++ > util/async.c | 11 +++++++++++ > util/qemu-coroutine-sleep.c | 11 +++++++++++ > util/qemu-coroutine.c | 11 +++++++++++ > 4 files changed, 39 insertions(+) > > diff --git a/include/qemu/coroutine_int.h b/include/qemu/coroutine_int.h > index cb98892..56e4c48 100644 > --- a/include/qemu/coroutine_int.h > +++ b/include/qemu/coroutine_int.h > @@ -53,6 +53,12 @@ struct Coroutine { > > /* Only used when the coroutine has yielded. */ > AioContext *ctx; > + > + /* Used to catch and abort on illegal co-routine entry. > + * Will contain the name of the function that had first > + * scheduled the coroutine. */ > + const char *scheduled;
Not sure if it makes any difference in practice, but I just want to mention that the new field is right after a cacheline boundary and the only field that is used in qemu_aio_coroutine_enter() and accesses this second cacheline. I'm not paying much attention to this kind of thing in most contexts, but entering a coroutine is a hot path that we want to be fast, so maybe it's worth having a second look. Kevin