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Date: Tue, 11 Jan 2011 09:28:25 +0100 (CET)
From: Thomas Gleixner <tglx@linutronix.de>
To: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
cc: David Ahern <daahern@cisco.com>, Ingo Molnar <mingo@elte.hu>,
        Peter Zijlstra <peterz@infradead.org>, tzanussi@gmail.com,
        Paul Mackerras <paulus@samba.org>, imunsie@au1.ibm.com,
        linux-kernel@vger.kernel.org, linux-perf-users@vger.kernel.org
Subject: Re: perf: commit 55b4462 causes perf record to hang
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On Mon, 10 Jan 2011, Arnaldo Carvalho de Melo wrote:

> Em Mon, Jan 10, 2011 at 11:47:43AM -0700, David Ahern escreveu:
> > With latest version of perf-core branch, a variant of perf record hangs:
> > # /tmp/build-perf/perf record -v -e cs -fo /tmp/perf.data  -- sleep 1
> > [ perf record: Captured and wrote 0.003 MB /tmp/perf.data (~120 samples) ]
> > 
> > It sits there forever. Back trace is:
> > 
> > (gdb) bt
> > #0  0x0000000000447658 in __perf_session__process_events (session=0xab9500, data_offset=208, data_size=2896, file_size=3104, ops=0x685580) at util/session.c:1006
> > #1  0x00000000004107dd in process_buildids () at builtin-record.c:466
> > #2  0x000000000041084d in atexit_header () at builtin-record.c:477
>  
> > git bisect traced the hang to
> > 
> > commit 55b44629f599a2305265ae9c77f9d9bcfd6ddc17
> > Author: Thomas Gleixner <tglx@linutronix.de>
> > Date:   Tue Nov 30 17:49:46 2010 +0000
> 
> Can you try with this patch, not reverting tglx's patch?
> 
> diff --git a/tools/perf/util/session.c b/tools/perf/util/session.c
> index 6fb4694..313dac2 100644
> --- a/tools/perf/util/session.c
> +++ b/tools/perf/util/session.c
> @@ -1007,7 +1007,7 @@ more:
>  	if (size == 0)
>  		size = 8;
>  
> -	if (head + event->header.size >= mmap_size) {
> +	if (head + event->header.size > mmap_size) {
>  		if (mmaps[map_idx]) {
>  			munmap(mmaps[map_idx], mmap_size);
>  			mmaps[map_idx] = NULL;
> 

/me feels stupid

      tglx