On Wed, 24 Apr 2019, Petr Mladek wrote: > WARN_ON_ONCE() could not be called safely under rq lock because > of console deadlock issues. Fortunately, simple printk_deferred() > is enough because the warning is printed from a well defined > location and context. > > Also klp_try_switch_task() is called under klp_mutex. > Therefore, the buffer for debug messages could be static. > > Signed-off-by: Petr Mladek <[email protected]> > --- > kernel/livepatch/transition.c | 19 ++++++++++++++----- > 1 file changed, 14 insertions(+), 5 deletions(-) > > diff --git a/kernel/livepatch/transition.c b/kernel/livepatch/transition.c > index 9c89ae8b337a..e8183d18227f 100644 > --- a/kernel/livepatch/transition.c > +++ b/kernel/livepatch/transition.c > @@ -254,6 +254,7 @@ static int klp_check_stack_func(struct klp_func *func, > static int klp_check_stack(struct task_struct *task, char *err_buf) > { > static unsigned long entries[MAX_STACK_ENTRIES]; > + static int enosys_warned; > struct stack_trace trace; > struct klp_object *obj; > struct klp_func *func; > @@ -263,8 +264,16 @@ static int klp_check_stack(struct task_struct *task, > char *err_buf) > trace.nr_entries = 0; > trace.max_entries = MAX_STACK_ENTRIES; > trace.entries = entries; > + > ret = save_stack_trace_tsk_reliable(task, &trace); > - WARN_ON_ONCE(ret == -ENOSYS); > + if (ret == -ENOSYS) { > + if (!enosys_warned) { > + printk_deferred(KERN_WARNING "%s: > save_stack_trace_tsk_reliable() not supported on this architecture.\n", > + __func__); > + enosys_warned = 1;
... abusing the fact that you are also printk maintainer :) ... looking at the above, wouldn't it make sense to introduce generic printk_deferred_once() instead? -- Jiri Kosina SUSE Labs
