On Tue, 15 Jul 2025 12:29:12 +0200
Peter Zijlstra [off-list ref] wrote:
quoted hunk ↗ jump to hunk
@@ -170,41 +193,62 @@ static void unwind_deferred_task_work(st
int unwind_deferred_request(struct unwind_work *work, u64 *cookie)
{
struct unwind_task_info *info = ¤t->unwind_info;
- int ret;
+ unsigned long bits, mask;
+ int bit, ret;
*cookie = 0;
- if (WARN_ON_ONCE(in_nmi()))
- return -EINVAL;
-
if ((current->flags & (PF_KTHREAD | PF_EXITING)) ||
!user_mode(task_pt_regs(current)))
return -EINVAL;
+ /* NMI requires having safe cmpxchg operations */
+ if (WARN_ON_ONCE(!UNWIND_NMI_SAFE && in_nmi()))
+ return -EINVAL;
I don't think we want to have a WARN_ON() here as the perf series tries
to first do the deferred unwinding and if that fails, it will go back
to it's old method.
By having a WARN_ON(), we need to make perf aware of this limitation
too. Do we want to do that?
-- Steve