On Fri, Oct 23, 2020 at 03:53:47PM -0400, Michael Jeanson wrote:
> -#define __DO_TRACE(tp, proto, args, cond, rcuidle) \
> +#define __DO_TRACE(tp, proto, args, cond, rcuidle, tp_flags) \
> do { \
> struct tracepoint_func *it_func_ptr; \
> void *it_func; \
> void *__data; \
> int __maybe_unused __idx = 0; \
> + bool maysleep = (tp_flags) & TRACEPOINT_MAYSLEEP; \
> \
> if (!(cond)) \
> return; \
> @@ -170,8 +178,13 @@ static inline struct tracepoint *tracepoint_ptr_deref(tracepoint_ptr_t *p)
> /* srcu can't be used from NMI */ \
> WARN_ON_ONCE(rcuidle && in_nmi()); \
> \
> - /* keep srcu and sched-rcu usage consistent */ \
> - preempt_disable_notrace(); \
> + if (maysleep) { \
> + might_sleep(); \
The main purpose of the patch set is to access user memory in tracepoints, right?
In such case I suggest to use stronger might_fault() here.
We used might_sleep() in sleepable bpf and it wasn't enough to catch
a combination where sleepable hook was invoked while mm->mmap_lock was
taken which may cause a deadlock.
> + rcu_read_lock_trace(); \
> + } else { \
> + /* keep srcu and sched-rcu usage consistent */ \
> + preempt_disable_notrace(); \
> + } \
