Now that vhost_task provides an API to safely wake a task without relying
on the caller to react to signalas, make handle_sigkill() optional and
WARN if the "unsafe" vhost_task_wake() is used without hooking sigkill.
Requiring the user to react to sigkill adds no meaningful value, e.g. it
didn't help KVM do anything useful, and adding a sanity check in
vhost_task_wake() gives developers a hint as to what needs to be done in
response to sigkill.
Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
---
kernel/vhost_task.c | 10 +++++++++-
1 file changed, 9 insertions(+), 1 deletion(-)
diff --git a/kernel/vhost_task.c b/kernel/vhost_task.c
index 5aa8ddf88d01..e0ec6bfe61e6 100644
--- a/kernel/vhost_task.c
+++ b/kernel/vhost_task.c
@@ -59,7 +59,8 @@ static int vhost_task_fn(void *data)
*/
if (!test_bit(VHOST_TASK_FLAGS_STOP, &vtsk->flags)) {
set_bit(VHOST_TASK_FLAGS_KILLED, &vtsk->flags);
- vtsk->handle_sigkill(vtsk->data);
+ if (vtsk->handle_sigkill)
+ vtsk->handle_sigkill(vtsk->data);
}
mutex_unlock(&vtsk->exit_mutex);
complete(&vtsk->exited);
@@ -81,6 +82,13 @@ static void __vhost_task_wake(struct vhost_task *vtsk)
*/
void vhost_task_wake(struct vhost_task *vtsk)
{
+ /*
+ * Waking the task without taking exit_mutex is safe if and only if the
+ * implementation hooks sigkill, as that's the only way the caller can
+ * know if the task has exited prematurely due to a signal.
+ */
+ WARN_ON_ONCE(!vtsk->handle_sigkill);
+
/*
* Checking VHOST_TASK_FLAGS_KILLED can race with signal delivery, but
* a race can only result in false negatives and this is just a sanity
--
2.51.0.261.g7ce5a0a67e-goog
