Re: [PATCH] perf test: Handle fd gaps in test__dso_data_reopen

[Arnaldo Carvalho de Melo <acme@kernel.org>]

Em Fri, Jul 30, 2021 at 02:19:58PM +0200, Michael Petlan escreveu:
> On Wed, 30 Jun 2021, Michael Petlan wrote:
> > On Fri, 25 Jun 2021, Eirik Fuller wrote:
> > > https://github.com/beaker-project/restraint/issues/215 describes a file
> > > descriptor leak which revealed the test failure described here.
> > > 
> > > The 'DSO data reopen' perf test assumes that RLIMIT_NOFILE limits the
> > > number of open file descriptors, but it actually limits newly opened
> > > file descriptors. When the file descriptor limit is reduced, file
> > > descriptors already open remain open regardless of the new limit. This
> > > test failure does not occur if open file descriptors are contiguous,
> > > beginning at zero.
> > > 
> > > The following command triggers this perf test failure.
> > > 
> > > perf test 'DSO data reopen' 3>/dev/null 8>/dev/null
> > > 
> > > This patch determines the file descriptor limit by opening four files
> > > and then closing them. The limit is set to the fourth file descriptor,
> > > leaving only the first three available because any newly opened file
> > > descriptor must be less than the limit.
> > > 
> > > Signed-off-by: Eirik Fuller <efuller@redhat.com>
> > 
> > Acked-by: Michael Petlan <mpetlan@redhat.com>
> 
> Hi Arnaldo,
> kindly reminder, could this get merged?

Thanks, applied. Sorry for the delay.

- Arnaldo

 
> Thank you.
> 
> > 
> > > ---
> > >  tools/perf/tests/dso-data.c | 14 ++++++++++++--
> > >  1 file changed, 12 insertions(+), 2 deletions(-)
> > > 
> > > diff --git a/tools/perf/tests/dso-data.c b/tools/perf/tests/dso-data.c
> > > index 627c1aaf1c9e..43e1b01e5afc 100644
> > > --- a/tools/perf/tests/dso-data.c
> > > +++ b/tools/perf/tests/dso-data.c
> > > @@ -308,10 +308,20 @@ int test__dso_data_cache(struct test *test __maybe_unused, int subtest __maybe_u
> > >  	return 0;
> > >  }
> > >  
> > > +static long new_limit(int count)
> > > +{
> > > +	int fd = open("/dev/null", O_RDONLY);
> > > +	long ret = fd;
> > > +	if (count > 0)
> > > +		ret = new_limit(--count);
> > > +	close(fd);
> > > +	return ret;
> > > +}
> > > +
> > >  int test__dso_data_reopen(struct test *test __maybe_unused, int subtest __maybe_unused)
> > >  {
> > >  	struct machine machine;
> > > -	long nr_end, nr = open_files_cnt();
> > > +	long nr_end, nr = open_files_cnt(), lim = new_limit(3);
> > >  	int fd, fd_extra;
> > >  
> > >  #define dso_0 (dsos[0])
> > > @@ -334,7 +344,7 @@ int test__dso_data_reopen(struct test *test __maybe_unused, int subtest __maybe_
> > >  
> > >  	/* Make sure we are able to open 3 fds anyway */
> > >  	TEST_ASSERT_VAL("failed to set file limit",
> > > -			!set_fd_limit((nr + 3)));
> > > +			!set_fd_limit((lim)));
> > >  
> > >  	TEST_ASSERT_VAL("failed to create dsos\n", !dsos__create(3, TEST_FILE_SIZE));
> > >  
> > > -- 
> > > 2.27.0
> > > 
> > > 
> > 
> > 
> 

-- 

- Arnaldo