Livepatch relies on stack checking of sleeping tasks to switch kthreads, so a busy kthread can block a livepatch transition indefinitely. We've seen this happen fairly often with busy vhost kthreads. Add a check to call klp_switch_current() from vhost_worker() when a livepatch is pending. In testing this allowed vhost kthreads to switch immediately when they had previously blocked livepatch transitions for long periods of time. Signed-off-by: Seth Forshee (DigitalOcean) <sforshee@xxxxxxxxxx> --- drivers/vhost/vhost.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c index cbe72bfd2f1f..d8624f1f2d64 100644 --- a/drivers/vhost/vhost.c +++ b/drivers/vhost/vhost.c @@ -30,6 +30,7 @@ #include <linux/interval_tree_generic.h> #include <linux/nospec.h> #include <linux/kcov.h> +#include <linux/livepatch.h> #include "vhost.h" @@ -366,6 +367,9 @@ static int vhost_worker(void *data) if (need_resched()) schedule(); } + + if (unlikely(klp_patch_pending(current))) + klp_switch_current(); } kthread_unuse_mm(dev->mm); return 0; -- b4 0.10.1
