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Date: Tue, 23 Sep 2014 14:24:37 +0200
From: Jiri Olsa <jolsa@redhat.com>
To: Namhyung Kim <namhyung@kernel.org>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>,
        Peter Zijlstra <a.p.zijlstra@chello.nl>,
        Ingo Molnar <mingo@kernel.org>, Paul Mackerras <paulus@samba.org>,
        Namhyung Kim <namhyung.kim@lge.com>,
        LKML <linux-kernel@vger.kernel.org>,
        Jean Pihet <jean.pihet@linaro.org>, Arun Sharma <asharma@fb.com>
Subject: Re: [PATCH 1/2] perf callchain: Create an address space per thread
Message-ID: <20140923122437.GE2979@krava.brq.redhat.com>
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On Tue, Sep 23, 2014 at 03:30:27PM +0900, Namhyung Kim wrote:
> The unw_addr_space_t in libunwind represents an address space to be
> used for stack unwinding.  It doesn't need to be create/destory
> everytime to unwind callchain (as in get_entries) and can have a same
> lifetime as thread (unless exec called).
> 
> So move the address space construction/destruction logic to the thread
> lifetime handling functions.  This is a preparation to enable caching
> in the unwind library.
> 
> Cc: Jiri Olsa <jolsa@redhat.com>
> Cc: Jean Pihet <jean.pihet@linaro.org>
> Cc: Arun Sharma <asharma@fb.com>
> Signed-off-by: Namhyung Kim <namhyung@kernel.org>
> ---
>  tools/perf/util/thread.c           |  8 ++++++++
>  tools/perf/util/unwind-libunwind.c | 30 +++++++++++++++++++++++++-----
>  tools/perf/util/unwind.h           | 17 +++++++++++++++++
>  3 files changed, 50 insertions(+), 5 deletions(-)
> 
> diff --git a/tools/perf/util/thread.c b/tools/perf/util/thread.c
> index a9df7f2c6dc9..c1fa4a3597ea 100644
> --- a/tools/perf/util/thread.c
> +++ b/tools/perf/util/thread.c
> @@ -7,6 +7,7 @@
>  #include "util.h"
>  #include "debug.h"
>  #include "comm.h"
> +#include "unwind.h"
>  
>  int thread__init_map_groups(struct thread *thread, struct machine *machine)
>  {
> @@ -48,6 +49,12 @@ struct thread *thread__new(pid_t pid, pid_t tid)
>  			goto err_thread;
>  
>  		list_add(&comm->list, &thread->comm_list);
> +
> +		if (unwind__prepare_access(thread) < 0) {

you could call list_add below this call and thus save
the list_del call below in error path

looks like you dont need comm to be on comm_list within
the unwind__prepare_access call

> +			list_del(&comm->list);
> +			free(comm);
> +			goto err_thread;
> +		}
>  	}

SNIP

jirka