On 08/06, Oleg Nesterov wrote: > > But, with or without this fix, shouldn't we set .disabled = 1 if modify_() > fails? > IIUC this doesn't matter, bp->attr.disabled is not really used anyway, but > looks a > bit confusing.
I am looking at another caller perf_event_modify_breakpoint(). It too doesn't set attr.disabled = 1 on failure, it does _perf_event_enable() instead so attr.disabled should be correct. But this looks wrong. If modify_user_hw_breakpoint_check() paths fails after arch_validate_hwbkpt_settings() was called, then we can not simply restore bp_addr/bp_type/bp_len and do _perf_event_enable(). We need another modify_user_hw_breakpoint_check() or validate_hw_breakpoint(). Note that arch_validate_hwbkpt_settings() updates arch_hw_breakpoint according to bp.attr, the restored bp->attr.bp_addr/bp_typebp_len have no effect if we call _perf_event_enable() after the failure. Or I am totally confused? Oleg.
