summaryrefslogtreecommitdiff
path: root/samples/livepatch/livepatch-sample.c
diff options
context:
space:
mode:
authorMiroslav Benes <mbenes@suse.cz>2018-01-10 11:01:28 +0100
committerJiri Kosina <jkosina@suse.cz>2018-01-11 10:58:03 +0100
commitd0807da78e11d46f18399cbf8c4028c731346766 (patch)
tree7421d9d68ae0d159c816995564984a0c0cfcc26a /samples/livepatch/livepatch-sample.c
parentc99a2be790b07752d8cc694434d3450afd4c5a00 (diff)
livepatch: Remove immediate feature
Immediate flag has been used to disable per-task consistency and patch all tasks immediately. It could be useful if the patch doesn't change any function or data semantics. However, it causes problems on its own. The consistency problem is currently broken with respect to immediate patches. func a patches 1i 2i 3 When the patch 3 is applied, only 2i function is checked (by stack checking facility). There might be a task sleeping in 1i though. Such task is migrated to 3, because we do not check 1i in klp_check_stack_func() at all. Coming atomic replace feature would be easier to implement and more reliable without immediate. Thus, remove immediate feature completely and save us from the problems. Note that force feature has the similar problem. However it is considered as a last resort. If used, administrator should not apply any new live patches and should plan for reboot into an updated kernel. The architectures would now need to provide HAVE_RELIABLE_STACKTRACE to fully support livepatch. Signed-off-by: Miroslav Benes <mbenes@suse.cz> Acked-by: Josh Poimboeuf <jpoimboe@redhat.com> Signed-off-by: Jiri Kosina <jkosina@suse.cz>
Diffstat (limited to 'samples/livepatch/livepatch-sample.c')
-rw-r--r--samples/livepatch/livepatch-sample.c15
1 files changed, 0 insertions, 15 deletions
diff --git a/samples/livepatch/livepatch-sample.c b/samples/livepatch/livepatch-sample.c
index 84795223f15f..2d554dd930e2 100644
--- a/samples/livepatch/livepatch-sample.c
+++ b/samples/livepatch/livepatch-sample.c
@@ -71,21 +71,6 @@ static int livepatch_init(void)
{
int ret;
- if (!klp_have_reliable_stack() && !patch.immediate) {
- /*
- * WARNING: Be very careful when using 'patch.immediate' in
- * your patches. It's ok to use it for simple patches like
- * this, but for more complex patches which change function
- * semantics, locking semantics, or data structures, it may not
- * be safe. Use of this option will also prevent removal of
- * the patch.
- *
- * See Documentation/livepatch/livepatch.txt for more details.
- */
- patch.immediate = true;
- pr_notice("The consistency model isn't supported for your architecture. Bypassing safety mechanisms and applying the patch immediately.\n");
- }
-
ret = klp_register_patch(&patch);
if (ret)
return ret;