linux-kernel - Re: [PATCH 3/4] perf map: Set kmap->kmaps backpointer for main kernel map chunks

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Date:   Mon, 10 Feb 2020 16:46:49 +0530
From:   Ravi Bangoria <ravi.bangoria@...ux.ibm.com>
To:     Jiri Olsa <jolsa@...hat.com>
Cc:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        Ingo Molnar <mingo@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Jiri Olsa <jolsa@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Clark Williams <williams@...hat.com>,
        linux-kernel@...r.kernel.org, linux-perf-users@...r.kernel.org,
        Arnaldo Carvalho de Melo <acme@...hat.com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Ravi Bangoria <ravi.bangoria@...ux.ibm.com>
Subject: Re: [PATCH 3/4] perf map: Set kmap->kmaps backpointer for main kernel
 map chunks



On 2/10/20 6:07 AM, Jiri Olsa wrote:
> On Sun, Feb 09, 2020 at 08:32:38PM +0100, Jiri Olsa wrote:
> 
> SNIP
> 
>>>>
>>>> perf top from perf/core has started crashing at __map__is_kernel():
>>>>
>>>>    (gdb) bt
>>>>    #0  __map__is_kernel (map=<optimized out>) at util/map.c:935
>>>>    #1  0x000000000045551d in perf_event__process_sample (machine=0xbab8f8,
>>>>        sample=0x7fffe5ffa6d0, evsel=0xba7570, event=0xbcac50, tool=0x7fffffff84e0)
>>>>        at builtin-top.c:833
>>>>    #2  deliver_event (qe=<optimized out>, qevent=<optimized out>) at builtin-top.c:1192
>>>>    #3  0x000000000050b9fb in do_flush (show_progress=false, oe=0x7fffffff87e0)
>>>>        at util/ordered-events.c:244
>>>>    #4  __ordered_events__flush (oe=oe@...ry=0x7fffffff87e0, how=how@...ry=OE_FLUSH__TOP,
>>>>        timestamp=timestamp@...ry=0) at util/ordered-events.c:323
>>>>    #5  0x000000000050c1b5 in __ordered_events__flush (timestamp=<optimized out>,
>>>>        how=<optimized out>, oe=<optimized out>) at util/ordered-events.c:339
>>>>    #6  ordered_events__flush (how=OE_FLUSH__TOP, oe=0x7fffffff87e0) at util/ordered-events.c:341
>>>>    #7  ordered_events__flush (oe=oe@...ry=0x7fffffff87e0, how=how@...ry=OE_FLUSH__TOP)
>>>>        at util/ordered-events.c:339
>>>>    #8  0x0000000000454e21 in process_thread (arg=0x7fffffff84e0) at builtin-top.c:1104
>>>>    #9  0x00007ffff7f2c4e2 in start_thread () from /lib64/libpthread.so.0
>>>>    #10 0x00007ffff76086d3 in clone () from /lib64/libc.so.6
>>>>
>>>> I haven't debugged it much but seems like the actual patch that's causing the
>>>> crash is de90d513b246 ("perf map: Use map->dso->kernel + map__kmaps() in
>>>> map__kmaps()").
>>>>
>>>> Did you face this / aware of it?
>>>
>>> hum, looks like there are few more places where we don't set
>>> kmaps pointer, patch below fixes that for me
>>>
>>> I'll still need to do more checking and I'll send a fix
>>>
>>> jirka
>>>
>>>
>>> ---
>>
>> I found one more place.. please check the attached patch
> 
> and third time's the charm.. hopefully ;-)
> 
> I made the fix more central.. it still needs to be split
> into several small fixes, but I'm running perf top for
> few hours now without the crash

I also kept it running for ~20 mins but didn't see the crash.
Feel free to add:

Tested-by: Ravi Bangoria <ravi.bangoria@...ux.ibm.com>