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Date:   Tue, 27 Oct 2020 12:59:07 +0100
From:   Jiri Olsa <jolsa@redhat.com>
To:     Alexey Budankov <alexey.budankov@linux.intel.com>
Cc:     Arnaldo Carvalho de Melo <acme@kernel.org>,
        Namhyung Kim <namhyung@kernel.org>,
        Alexander Shishkin <alexander.shishkin@linux.intel.com>,
        Adrian Hunter <adrian.hunter@intel.com>,
        Andi Kleen <ak@linux.intel.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Ingo Molnar <mingo@redhat.com>,
        linux-kernel <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v2 03/15] perf data: open data directory in read access
 mode
Message-ID: <20201027115907.GC2900849@krava>
References: <1ec29ed6-0047-d22f-630b-a7f5ccee96b4@linux.intel.com>
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 <20201024154317.GB2589351@krava>
 <a368355b-4bf3-05b8-9fa0-ee3feb58f8bf@linux.intel.com>
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On Mon, Oct 26, 2020 at 08:47:06PM +0300, Alexey Budankov wrote:
> 
> On 24.10.2020 18:43, Jiri Olsa wrote:
> > On Wed, Oct 21, 2020 at 06:57:53PM +0300, Alexey Budankov wrote:
> >>
> >> Open files located at trace data directory in case read access
> >> mode is requested. File are opened and its fds assigned to
> >> perf_data dir files especially for loading data directories
> >> content in perf report mode.
> >>
> >> Signed-off-by: Alexey Budankov <alexey.budankov@linux.intel.com>
> >> ---
> >>  tools/perf/util/data.c | 4 ++++
> >>  1 file changed, 4 insertions(+)
> >>
> >> diff --git a/tools/perf/util/data.c b/tools/perf/util/data.c
> >> index c47aa34fdc0a..6ad61ac6ba67 100644
> >> --- a/tools/perf/util/data.c
> >> +++ b/tools/perf/util/data.c
> >> @@ -321,6 +321,10 @@ static int open_dir(struct perf_data *data)
> >>  		return -1;
> >>  
> >>  	ret = open_file(data);
> >> +	if (!ret && perf_data__is_dir(data)) {
> >> +		if (perf_data__is_read(data))
> >> +			ret = perf_data__open_dir(data);
> >> +	}
> > 
> > perf_data__open_dir is also called from perf_session__new
> > is it called twice?
> 
> It is not called twice. It is in different branches.
> This one is for write and the other one is for read.

hum, is that right?

	# ./perf record --threads 
	^C[ perf record: Woken up 15 times to write data ]
	[ perf record: Captured and wrote 1.421 MB perf.data (515 samples) ]

	# gdb ./perf
	GNU gdb (GDB) Fedora 9.1-6.fc32

	(gdb) b perf_data__open_dir
	Breakpoint 1 at 0x5b4753: file util/data.c, line 72.

	(gdb) r --no-pager report --stdio
	Starting program: /home/jolsa/kernel/linux-perf/tools/perf/perf --no-pager report --stdio

	Breakpoint 1, perf_data__open_dir (data=0x7fffffffb0e0) at util/data.c:72
	72      {
	(gdb) bt
	#0  perf_data__open_dir (data=0x7fffffffb0e0) at util/data.c:72
	#1  0x00000000005b538d in open_dir (data=0x7fffffffb0e0) at util/data.c:326
	#2  0x00000000005b546d in perf_data__open (data=0x7fffffffb0e0) at util/data.c:351
	#3  0x00000000005627e8 in perf_session__new (data=0x7fffffffb0e0, repipe=false, tool=0x7fffffffb220) at util/session.c:210
	#4  0x000000000045a572 in cmd_report (argc=0, argv=0x7fffffffd7a8) at builtin-report.c:1372
	#5  0x00000000004f49ec in run_builtin (p=0xaadab0 <commands+240>, argc=2, argv=0x7fffffffd7a8) at perf.c:312
	#6  0x00000000004f4c59 in handle_internal_command (argc=2, argv=0x7fffffffd7a8) at perf.c:364
	#7  0x00000000004f4da0 in run_argv (argcp=0x7fffffffd5ec, argv=0x7fffffffd5e0) at perf.c:408
	#8  0x00000000004f516c in main (argc=2, argv=0x7fffffffd7a8) at perf.c:538

	(gdb) c
	Continuing.

	Breakpoint 1, perf_data__open_dir (data=0x7fffffffb0e0) at util/data.c:72
	72      {
	(gdb) bt
	#0  perf_data__open_dir (data=0x7fffffffb0e0) at util/data.c:72
	#1  0x0000000000562883 in perf_session__new (data=0x7fffffffb0e0, repipe=false, tool=0x7fffffffb220) at util/session.c:234
	#2  0x000000000045a572 in cmd_report (argc=0, argv=0x7fffffffd7a8) at builtin-report.c:1372
	#3  0x00000000004f49ec in run_builtin (p=0xaadab0 <commands+240>, argc=2, argv=0x7fffffffd7a8) at perf.c:312
	#4  0x00000000004f4c59 in handle_internal_command (argc=2, argv=0x7fffffffd7a8) at perf.c:364
	#5  0x00000000004f4da0 in run_argv (argcp=0x7fffffffd5ec, argv=0x7fffffffd5e0) at perf.c:408
	#6  0x00000000004f516c in main (argc=2, argv=0x7fffffffd7a8) at perf.c:538


AFAICS the second (current) call to perf_data__open_dir will
do the job, because the call you added still does not see
directory with proper version and will bail out on call to
  perf_data__is_single_file

perf_session__open call will read headers and update dir version
so the current perf_data__open_dir will open the directory

jirka