Quoting Seth Arnold (seth.arn...@canonical.com): > On Thu, Apr 11, 2013 at 11:43:31AM -0500, Serge Hallyn wrote: > > 1. in container_free, set c->privlock to NULL before calling > > sem_destroy, to prevent a window where another thread could call > > sem_wait(c->privlock) while c->privlock is not NULL but is already > > destroyed. > > > > 2. in container_get, check for numthreads < 0 before calling lxclock. > > Once numthreads is 0, it never goes back up. > > > > Following is a comment added to lxccontainer.c: > > > > /* > > * Consider the following case: > > freer | racing get()er > > ================================================================== > > lxc_container_put() | lxc_container_get() > > \ lxclock(c->privlock) | c->numthreads < 1? (no) > > \ c->numthreads = 0 | \ lxclock(c->privlock) -> waits > > \ lxcunlock() | \ > > \ lxc_container_free() | \ lxclock() returns > > | \ c->numthreads < 1 -> return 0 > > \ \ (free stuff) | > > \ \ sem_destroy(privlock) | > > > > * When the get()er checks numthreads the first time, one of the following > > * is true: > > * 1. freer has set numthreads = 0. get() returns 0 > > * 2. freer is between lxclock and setting numthreads to 0. get()er will > > * sem_wait on privlock, get lxclock after freer() drops it, then see > > * numthreads is 0 and exit without touching lxclock again.. > > * 3. freer has not yet locked privlock. If get()er runs first, then > > put()er > > * will see --numthreads = 1 and not call lxc_container_free(). > > */ > > > > Signed-off-by: Serge Hallyn <serge.hal...@ubuntu.com> > > Acked-by: Seth Arnold <seth.arn...@canonical.com>
Thanks Seth! (For the list, Seth pointed out the original problems) -serge ------------------------------------------------------------------------------ Precog is a next-generation analytics platform capable of advanced analytics on semi-structured data. The platform includes APIs for building apps and a phenomenal toolset for data science. Developers can use our toolset for easy data analysis & visualization. Get a free account! http://www2.precog.com/precogplatform/slashdotnewsletter _______________________________________________ Lxc-devel mailing list Lxc-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/lxc-devel
