Messages in this thread | | | Date | Mon, 6 Aug 2018 15:07:31 +0200 | From | Oleg Nesterov <> | Subject | Re: [PATCH 2/2] perf/hw_breakpoint: Modify breakpoint even if the new attr has disabled set |
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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.
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