Well. I am not familiar with this code, and when I tried to read it I feel I will be never able to understand it ;) On 05/20, Vince Weaver wrote: > > on 3.10-rc1 with the trinity fuzzer patched to exercise the > perf_event_open() syscall I am triggering this WARN_ONCE: > > [ 75.864822] ------------[ cut here ]------------ > [ 75.864830] WARNING: at arch/x86/kernel/hw_breakpoint.c:121 arch_install_hw_breakpoint+0x5b/0xcb() ... > [ 75.864916] [<ffffffff81006fff>] ? arch_install_hw_breakpoint+0x5b/0xcb > [ 75.864919] [<ffffffff810ab5a1>] ? event_sched_in+0x68/0x11c I am wondering if we should check attr->pinned before WARN_ONCE... But it seems that hw_breakpoint.c is buggy anyway. Suppose that attr.task != NULL and event->cpu = -1. __reserve_bp_slot() tries to calculate slots.pinned and calls fetch_bp_busy_slots(). In this case fetch_bp_busy_slots() does for_each_online_cpu(cpu) ... nr += task_bp_pinned(cpu, bp, type); And task_bp_pinned() (in particular) checks cpu == event->cpu, this will be never true. IOW, it seems that __reserve_bp_slot(task, cpu => -1) always succeeds because task_bp_pinned() returns 0 and thus we can create more than HWP_NUM breakpoints. Much more ;) As for _create, I guess we probably need something like --- x/kernel/events/hw_breakpoint.c +++ x/kernel/events/hw_breakpoint.c @@ -156,7 +156,7 @@ fetch_bp_busy_slots(struct bp_busy_slots if (!tsk) nr += max_task_bp_pinned(cpu, type); else - nr += task_bp_pinned(cpu, bp, type); + nr += task_bp_pinned(-1, bp, type); if (nr > slots->pinned) slots->pinned = nr; But I simply can't understand toggle_bp_task_slot()->task_bp_pinned(). Oleg. -- To unsubscribe from this list: send the line "unsubscribe trinity" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
